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Publisher: Elsevier   (Total: 3160 journals)

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Showing 1201 - 1400 of 3160 Journals sorted alphabetically
Growth Factors and Cytokines in Health and Disease     Full-text available via subscription   (Followers: 1)
Growth Hormone & IGF Research     Hybrid Journal   (Followers: 17, SJR: 1.059, CiteScore: 2)
Gynecologic Oncology     Hybrid Journal   (Followers: 25, SJR: 2.339, CiteScore: 4)
Gynecologic Oncology Reports     Open Access   (Followers: 10, SJR: 0.307, CiteScore: 1)
Gynécologie Obstétrique & Fertilité     Full-text available via subscription   (Followers: 1)
Habitat Intl.     Hybrid Journal   (Followers: 6, SJR: 1.336, CiteScore: 3)
Hand Clinics     Full-text available via subscription   (Followers: 5, SJR: 0.556, CiteScore: 1)
Hand Surgery and Rehabilitation     Full-text available via subscription   (Followers: 4, SJR: 0.358, CiteScore: 1)
Handai Nanophotonics     Full-text available via subscription  
Handbook of Adhesives and Sealants     Full-text available via subscription   (Followers: 2)
Handbook of Agricultural Economics     Full-text available via subscription   (Followers: 3)
Handbook of Algebra     Full-text available via subscription  
Handbook of Analytical Separations     Full-text available via subscription   (Followers: 3)
Handbook of Behavioral Neuroscience     Full-text available via subscription   (Followers: 3)
Handbook of Biological Physics     Full-text available via subscription  
Handbook of Chemical Neuroanatomy     Full-text available via subscription  
Handbook of Clinical Neurology     Full-text available via subscription   (Followers: 2, SJR: 1.007, CiteScore: 2)
Handbook of Clinical Neurophysiology     Full-text available via subscription  
Handbook of Complex Analysis     Full-text available via subscription  
Handbook of Computational Economics     Full-text available via subscription   (Followers: 2, SJR: 4.16, CiteScore: 2)
Handbook of Defense Economics     Full-text available via subscription   (Followers: 2)
Handbook of Development Economics     Full-text available via subscription   (Followers: 8)
Handbook of Differential Equations: Evolutionary Equations     Full-text available via subscription  
Handbook of Differential Equations: Ordinary Differential Equations     Full-text available via subscription  
Handbook of Differential Equations: Stationary Partial Differential Equations     Full-text available via subscription   (Followers: 2)
Handbook of Differential Geometry     Full-text available via subscription  
Handbook of Dynamical Systems     Full-text available via subscription   (Followers: 1)
Handbook of Econometrics     Full-text available via subscription   (Followers: 10)
Handbook of Economic Forecasting     Full-text available via subscription   (Followers: 3)
Handbook of Economic Growth     Full-text available via subscription   (Followers: 3)
Handbook of Environmental Economics     Full-text available via subscription   (Followers: 3)
Handbook of Experimental Economics Results     Full-text available via subscription   (Followers: 6)
Handbook of Exploration and Environmental Geochemistry     Full-text available via subscription   (Followers: 2)
Handbook of Exploration Geochemistry     Full-text available via subscription   (Followers: 1)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Game Theory with Economic Applications     Full-text available via subscription   (Followers: 1)
Handbook of Geophysical Exploration: Seismic Exploration     Full-text available via subscription  
Handbook of Health Economics     Full-text available via subscription   (Followers: 13)
Handbook of Immunohistochemistry and in Situ Hybridization of Human Carcinomas     Full-text available via subscription   (Followers: 1)
Handbook of Income Distribution     Full-text available via subscription   (Followers: 4)
Handbook of Industrial Organization     Full-text available via subscription   (Followers: 5)
Handbook of Intl. Economics     Full-text available via subscription  
Handbook of Labor Economics     Full-text available via subscription   (Followers: 14)
Handbook of Law and Economics     Full-text available via subscription   (Followers: 17)
Handbook of Macroeconomics     Full-text available via subscription   (Followers: 6, SJR: 0, CiteScore: 2)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2, SJR: 0.467, CiteScore: 2)
Handbook of Mathematical Economics     Full-text available via subscription  
Handbook of Mathematical Fluid Dynamics     Full-text available via subscription   (Followers: 2)
Handbook of Metal Physics     Full-text available via subscription  
Handbook of Monetary Economics     Full-text available via subscription   (Followers: 7)
Handbook of Natural Resource and Energy Economics     Full-text available via subscription   (Followers: 5)
Handbook of Numerical Analysis     Full-text available via subscription   (Followers: 5)
Handbook of Perception and Action     Full-text available via subscription   (Followers: 2)
Handbook of Petroleum Exploration and Production     Full-text available via subscription   (Followers: 2)
Handbook of Population and Family Economics     Full-text available via subscription   (Followers: 4)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 6)
Handbook of Public Economics     Full-text available via subscription   (Followers: 1)
Handbook of Regional and Urban Economics     Full-text available via subscription   (Followers: 3)
Handbook of Sensors and Actuators     Full-text available via subscription   (Followers: 10)
Handbook of Social Choice and Welfare     Full-text available via subscription   (Followers: 3)
Handbook of Statistics     Full-text available via subscription   (Followers: 8, SJR: 0.102, CiteScore: 0)
Handbook of Surface Science     Full-text available via subscription   (Followers: 4, SJR: 0.193, CiteScore: 0)
Handbook of Systemic Autoimmune Diseases     Full-text available via subscription   (Followers: 2)
Handbook of the Economics of Art and Culture     Full-text available via subscription   (Followers: 3)
Handbook of the Economics of Education     Full-text available via subscription   (Followers: 9, SJR: 0, CiteScore: 2)
Handbook of the Economics of Finance     Full-text available via subscription   (Followers: 6)
Handbook of the Economics of Giving, Altruism and Reciprocity     Full-text available via subscription   (Followers: 2)
Handbook of the Geometry of Banach Spaces     Full-text available via subscription   (Followers: 1)
Handbook of the History of Logic     Full-text available via subscription   (Followers: 1)
Handbook of Thermal Analysis and Calorimetry     Full-text available via subscription   (Followers: 1)
Handbook of Thermal Conductivity     Full-text available via subscription   (Followers: 4)
Handbook of Vapor Pressure     Full-text available via subscription  
Handbook on the Physics and Chemistry of Rare Earths     Full-text available via subscription   (Followers: 3, SJR: 0.755, CiteScore: 3)
Handbooks of Management Accounting Research     Full-text available via subscription   (Followers: 4)
HardwareX     Open Access  
Harmful Algae     Hybrid Journal   (Followers: 5, SJR: 1.531, CiteScore: 4)
HBRC J.     Open Access   (Followers: 2)
Health & Place     Hybrid Journal   (Followers: 15, SJR: 1.506, CiteScore: 3)
Health Outcomes Research in Medicine     Hybrid Journal   (Followers: 3)
Health Policy     Hybrid Journal   (Followers: 43, SJR: 1.252, CiteScore: 2)
Health Policy and Technology     Hybrid Journal   (Followers: 4, SJR: 0.322, CiteScore: 1)
Health Professions Education     Open Access   (Followers: 3)
Healthcare : The J. of Delivery Science and Innovation     Full-text available via subscription   (Followers: 1)
Hearing Research     Hybrid Journal   (Followers: 11, SJR: 1.35, CiteScore: 3)
Heart & Lung: The J. of Acute and Critical Care     Hybrid Journal   (Followers: 11, SJR: 0.757, CiteScore: 2)
Heart Failure Clinics     Full-text available via subscription   (Followers: 2, SJR: 1.153, CiteScore: 2)
Heart Rhythm     Hybrid Journal   (Followers: 11, SJR: 3.231, CiteScore: 4)
Heart, Lung and Circulation     Full-text available via subscription   (Followers: 9, SJR: 0.599, CiteScore: 1)
HeartRhythm Case Reports     Open Access   (SJR: 0.232, CiteScore: 0)
Heliyon     Open Access   (SJR: 0.355, CiteScore: 1)
Hellenic J. of Cardiology     Open Access   (Followers: 1, SJR: 0.479, CiteScore: 1)
Hematology, Transfusion and Cell Therapy     Open Access   (Followers: 1)
Hematology/Oncology and Stem Cell Therapy     Open Access   (Followers: 4, SJR: 0.532, CiteScore: 1)
Hematology/Oncology Clinics of North America     Full-text available via subscription   (Followers: 6, SJR: 1.282, CiteScore: 3)
Hepatobiliary & Pancreatic Diseases Intl.     Full-text available via subscription   (Followers: 2, SJR: 0.711, CiteScore: 2)
High Energy Density Physics     Hybrid Journal   (Followers: 2, SJR: 0.933, CiteScore: 2)
Hipertensión y Riesgo Vascular     Full-text available via subscription   (SJR: 0.115, CiteScore: 0)
Historia Mathematica     Full-text available via subscription   (Followers: 1, SJR: 0.174, CiteScore: 0)
History of CERN     Full-text available via subscription   (Followers: 1)
History of Neuroscience in Autobiography     Full-text available via subscription   (Followers: 3)
HIV & AIDS Review     Full-text available via subscription   (Followers: 12, SJR: 0.134, CiteScore: 0)
Homeopathy     Hybrid Journal   (Followers: 6, SJR: 0.678, CiteScore: 1)
HOMO - J. of Comparative Human Biology     Hybrid Journal   (Followers: 2, SJR: 0.335, CiteScore: 1)
Hong Kong J. of Nephrology     Open Access   (Followers: 2, SJR: 0.137, CiteScore: 0)
Hong Kong J. of Occupational Therapy     Open Access   (Followers: 43, SJR: 0.237, CiteScore: 1)
Hong Kong Physiotherapy J.     Open Access   (Followers: 14, SJR: 0.183, CiteScore: 0)
Hormigón y Acero     Full-text available via subscription  
Hormones and Behavior     Hybrid Journal   (Followers: 13, SJR: 1.638, CiteScore: 4)
Horticultural Plant J.     Open Access   (Followers: 5)
Hospital Medicine Clinics     Full-text available via subscription   (Followers: 2, SJR: 0.107, CiteScore: 0)
Human Factors in Information Technology     Full-text available via subscription   (Followers: 35)
Human Immunology     Hybrid Journal   (Followers: 18, SJR: 0.856, CiteScore: 2)
Human Movement Science     Hybrid Journal   (Followers: 15, SJR: 0.756, CiteScore: 2)
Human Pathology     Hybrid Journal   (Followers: 26, SJR: 1.304, CiteScore: 3)
Human Pathology : Case Reports     Open Access   (Followers: 2, SJR: 0.136, CiteScore: 0)
Human Resource Management Review     Hybrid Journal   (Followers: 54, SJR: 1.675, CiteScore: 4)
Hydrometallurgy     Hybrid Journal   (Followers: 13, SJR: 1.208, CiteScore: 3)
IATSS Research     Open Access   (SJR: 0.37, CiteScore: 1)
Icarus     Hybrid Journal   (Followers: 74, SJR: 2.037, CiteScore: 3)
ICT Express     Open Access   (SJR: 0.234, CiteScore: 1)
IDCases     Open Access   (SJR: 0.344, CiteScore: 1)
IERI Procedia     Open Access   (Followers: 1)
IFAC-PapersOnLine     Open Access   (SJR: 0.26, CiteScore: 1)
IIMB Management Review     Open Access   (Followers: 9, SJR: 0.24, CiteScore: 1)
IJC Heart & Vessels     Open Access   (Followers: 1)
IJC Heart & Vasculature     Open Access   (Followers: 1, SJR: 0.342, CiteScore: 1)
IJC Metabolic & Endocrine     Open Access   (Followers: 1, SJR: 0.4, CiteScore: 1)
Image and Vision Computing     Hybrid Journal   (Followers: 15, SJR: 0.612, CiteScore: 3)
Imagen Diagnóstica     Full-text available via subscription   (SJR: 0.106, CiteScore: 0)
Imagerie de la Femme     Full-text available via subscription   (Followers: 1, SJR: 0.124, CiteScore: 0)
Immunity     Full-text available via subscription   (Followers: 55, SJR: 13.393, CiteScore: 16)
Immuno-analyse & Biologie Spécialisée     Full-text available via subscription   (Followers: 2)
Immunobiology     Hybrid Journal   (Followers: 9, SJR: 1.1, CiteScore: 3)
Immunology and Allergy Clinics of North America     Full-text available via subscription   (Followers: 6, SJR: 1.132, CiteScore: 3)
Immunology Letters     Hybrid Journal   (Followers: 13, SJR: 1.168, CiteScore: 3)
Immunotoxicology of Drugs and Chemicals: an Experimental and Clinical Approach     Full-text available via subscription   (Followers: 1)
Implantodontie     Full-text available via subscription  
Indagationes Mathematicae     Open Access   (Followers: 1, SJR: 0.685, CiteScore: 1)
Indian Heart J.     Open Access   (Followers: 5, SJR: 0.333, CiteScore: 1)
Indian J. of Medical Specialities     Hybrid Journal   (SJR: 0.118, CiteScore: 0)
Indian J. of Tuberculosis     Full-text available via subscription   (SJR: 0.221, CiteScore: 0)
Indian Pacing and Electrophysiology J.     Open Access   (Followers: 1, SJR: 0.273, CiteScore: 0)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Crops and Products     Hybrid Journal   (Followers: 6, SJR: 1.091, CiteScore: 4)
Industrial Marketing Management     Hybrid Journal   (Followers: 23, SJR: 1.663, CiteScore: 4)
Industrial Safety Series     Full-text available via subscription   (Followers: 17)
Infant Behavior and Development     Hybrid Journal   (Followers: 14, SJR: 0.784, CiteScore: 2)
Infectio     Open Access   (SJR: 0.133, CiteScore: 0)
Infection, Disease & Health     Open Access   (Followers: 8, SJR: 0.23, CiteScore: 1)
Infection, Genetics and Evolution     Hybrid Journal   (Followers: 5, SJR: 1.278, CiteScore: 3)
Infectious Disease Clinics of North America     Full-text available via subscription   (Followers: 5, SJR: 2.359, CiteScore: 5)
Informatics in Medicine Unlocked     Open Access   (SJR: 0.224, CiteScore: 1)
Information & Management     Hybrid Journal   (Followers: 56, SJR: 1.628, CiteScore: 5)
Information and Computation     Hybrid Journal   (Followers: 4, SJR: 0.504, CiteScore: 1)
Information and Organization     Hybrid Journal   (Followers: 39, SJR: 1.202, CiteScore: 3)
Information and Software Technology     Hybrid Journal   (Followers: 6, SJR: 0.581, CiteScore: 4)
Information Economics and Policy     Hybrid Journal   (Followers: 5, SJR: 0.63, CiteScore: 1)
Information Fusion     Hybrid Journal   (Followers: 2, SJR: 1.832, CiteScore: 7)
Information Processing & Management     Hybrid Journal   (Followers: 417, SJR: 0.92, CiteScore: 4)
Information Processing in Agriculture     Open Access   (SJR: 0.352, CiteScore: 2)
Information Processing Letters     Hybrid Journal   (Followers: 6, SJR: 0.412, CiteScore: 1)
Information Sciences     Hybrid Journal   (Followers: 476, SJR: 1.635, CiteScore: 5)
Information Security Technical Report     Full-text available via subscription   (Followers: 12)
Information Systems     Hybrid Journal   (Followers: 13, SJR: 0.805, CiteScore: 4)
Infosecurity     Full-text available via subscription   (Followers: 11)
Infrared Physics & Technology     Hybrid Journal   (Followers: 12, SJR: 0.54, CiteScore: 2)
Injury     Hybrid Journal   (Followers: 18, SJR: 0.99, CiteScore: 2)
Injury Extra     Open Access   (Followers: 2)
Inmunología     Full-text available via subscription   (Followers: 2)
Innovative Food Science & Emerging Technologies     Hybrid Journal   (Followers: 5, SJR: 1.201, CiteScore: 3)
Inorganic Chemistry Communications     Hybrid Journal   (Followers: 13, SJR: 0.43, CiteScore: 2)
Inorganica Chimica Acta     Hybrid Journal   (Followers: 9, SJR: 0.485, CiteScore: 2)
Insect Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 3, SJR: 1.912, CiteScore: 4)
Instabilities in Silicon Devices     Full-text available via subscription   (Followers: 1)
Insulin     Full-text available via subscription   (Followers: 6)
Insurance: Mathematics and Economics     Hybrid Journal   (Followers: 9, SJR: 1.083, CiteScore: 2)
Integration, the VLSI J.     Hybrid Journal   (Followers: 6, SJR: 0.223, CiteScore: 1)
Integrative Medicine Research     Open Access   (Followers: 3)
Intellectual Economics     Open Access  
Intelligence     Hybrid Journal   (Followers: 7, SJR: 1.633, CiteScore: 3)
Intensive and Critical Care Nursing     Hybrid Journal   (Followers: 31, SJR: 0.611, CiteScore: 2)
Interdisciplinary Neurosurgery     Open Access   (SJR: 0.164, CiteScore: 0)
Interface Science and Technology     Full-text available via subscription  
Intermetallics     Hybrid Journal   (Followers: 22, SJR: 1.568, CiteScore: 4)
Internet Interventions : The application of information technology in mental and behavioural health     Open Access   (Followers: 4, SJR: 1.962, CiteScore: 4)
Interventional Cardiology Clinics     Full-text available via subscription   (Followers: 3, SJR: 0.156, CiteScore: 0)
Intl. Biodeterioration & Biodegradation     Hybrid Journal   (Followers: 1, SJR: 1.086, CiteScore: 4)
Intl. Business Review     Hybrid Journal   (Followers: 10, SJR: 1.012, CiteScore: 3)
Intl. Communications in Heat and Mass Transfer     Hybrid Journal   (Followers: 21, SJR: 1.553, CiteScore: 5)
Intl. Comparative Jurisprudence     Open Access   (Followers: 2)
Intl. Dairy J.     Hybrid Journal   (Followers: 6, SJR: 1.051, CiteScore: 2)
Intl. Economics     Hybrid Journal   (Followers: 3, SJR: 0.451, CiteScore: 1)
Intl. Emergency Nursing     Hybrid Journal   (Followers: 10, SJR: 0.461, CiteScore: 1)
Intl. Geophysics     Full-text available via subscription   (Followers: 3)
Intl. Immunopharmacology     Hybrid Journal   (Followers: 2, SJR: 1.051, CiteScore: 3)
Intl. J. for Parasitology     Hybrid Journal   (Followers: 11, SJR: 1.638, CiteScore: 4)
Intl. J. for Parasitology : Drugs and Drug Resistance     Open Access   (Followers: 4, SJR: 1.556, CiteScore: 4)
Intl. J. for Parasitology : Parasites and Wildlife     Open Access   (Followers: 2, SJR: 1.455, CiteScore: 3)
Intl. J. of Accounting     Hybrid Journal   (Followers: 1)
Intl. J. of Accounting Information Systems     Hybrid Journal   (Followers: 5, SJR: 0.399, CiteScore: 2)

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Similar Journals
Journal Cover
Hydrometallurgy
Journal Prestige (SJR): 1.208
Citation Impact (citeScore): 3
Number of Followers: 13  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0304-386X
Published by Elsevier Homepage  [3160 journals]
  • The impact of sulfate ions on the ion exchange of rare earth elements
    • Abstract: Publication date: Available online 20 March 2019Source: HydrometallurgyAuthor(s): Michael J. Page, James E. Quinn, Karin H. Soldenhoff The influence of sulfate versus chloride media on the adsorption of rare earth elements (REE) by strong acid and iminodiacetic acid resins was investigated. For the strong acid resin, Lewatit MonoPlus SP 112, the adsorption constants recorded for La, Sm and Er from MgSO4 solution were much lower compared to the values recorded from MgCl2 solution. The adsorption isotherms constructed for Sm from 0.5 M MgSO4 and 0.5 M MgCl2 solution also showed a substantial decrease in the equilibrium resin capacity that could be attained from sulfate solution. In addition, it was determined that the extraction strength of Sm from 0.5 M MgSO4 solution was unaffected by a change in solution pH from 1 to 3, despite the significant change in the aqueous speciation of SO42− and Sm3+ over this range. For the iminodiacetic acid resin, Purolite S930Plus, a similarly large decrease in the La adsorption constants was recorded from MgSO4 solution compared to MgCl2 solution which resulted in a large shift in the extraction curve to higher pH (pH50 = 1.9 in 1 M MgCl2 solution and 2.8 in 1 M MgSO4 solution). For both resins the decreased adsorption strength of the REE in sulfate solution also resulted in a decreased selectivity for the REE over key impurity ions. For instance the selectivity of the strong acid resin for Sm over Al was more than halved in MgSO4 versus MgCl2 solution, whereas the selectivity of the iminodiacetic acid resin for La over Mg decreased by an order of magnitude in MgSO4 versus MgCl2 solution (pH 4).
       
  • A detailed spectrophotometric investigation of the stability constants of
           [PdCln(OH)4-n]2− and [PdBrn(OH)4-n]2− (n = 0–4)
    • Abstract: Publication date: Available online 20 March 2019Source: HydrometallurgyAuthor(s): C.J. le Roux, R.J. Kriek Complex formation of mixed palladium (II) chloro-hydroxo and palladium(II) bromo-hydroxo complexes have been investigated employing spectrophotometry at 25 °C and an ionic strength of 1.0 M. Hyperquad Simulation and Speciation (HySS) was employed to determine the ideal titration conditions and an autotitrator (equipped with a flow-through cell) was used to accurately vary the pH over 80 and 90 intervals respectively. The stability constants (log βn) for the mixed chloro-hydroxo complexes [PdCl4-n(OH)n]2− (n = 0–4), are: log β1 = 18.36, log β2 = 23.21, log β3 = 26.91 and log β4 = 29.68. These newly obtained values represent a more accurate representation for the stability constants of the mixed palladium(II) chloro-hydroxo speciation. The same experimental procedure was employed to calculate, for the first time, the stepwise stability constants of the palladium(II) bromo-hydroxo system, [PdBr4-n(OH)n]2− (n = 0–4), i.e. log β1 = 18.73, log β2 = 22.25, log β3 = 25.58 and log β4 = 28.47. Molar absorption spectra for all the complexes in question have been obtained. For both systems, complete Pourbaix diagrams were constructed from the new speciation data showing the predominant species for each system.Graphical abstractUnlabelled Image
       
  • Leaching characteristics and mechanism of the synthetic calcium-aluminate
           slags for alumina recovery
    • Abstract: Publication date: Available online 19 March 2019Source: HydrometallurgyAuthor(s): Fabian Imanasa Azof, Yongxiang Yang, Dimitrios Panias, Leiv Kolbeinsen, Jafar Safarian The leaching characteristics and mechanism of synthetic CaO-Al2O3 slags in alkaline solution at atmospheric pressure have been studied. The purpose of the study is to have a better understanding of the leaching part of the Pedersen process, as an alternative to the Bayer process for alumina production. The crystalline slags containing CaAl2O4, Ca3Al2O6, CaAl4O7, and Ca12Al14O33 phases, and leaching residues (predominantly CaCO3) are characterized by X-ray Diffraction and semi-quantitative analysis. Of the leaching characteristics in a solution containing 120 g/L Na2CO3, the slag with the highest amount of Ca12Al14O33 phase is the most leachable one in the CaO-Al2O3 system with about 95% of alumina extraction. The leaching extent is confirmed employing Inductively Coupled Plasma-High Resolution-Mass Spectrometer (ICP-HR-MS) analysis, and it decreases by 0.4% for every percent of the bayerite (Al(OH)3) formation during the leaching. The less stable form of CaCO3, i.e., vaterite, is formed over the leached slag particles that consist 33–49 wt% CaO, while Ca3Al2(OH)12 (tricalcium alumina hydrate) precipitated at relatively low concentrations (< 6 wt%) in all residue. The non-bridging oxygen (NBO) over tetrahedral structure (T) index shows that the atomic structure may affect the leaching extent of the slags, the lower NBO/T index of the phase is the more difficult for the phase to leach or depolymerize. However, the Ca12Al14O33 phase is an exception case where it has “free” O-ions at the center of the cage structure, which makes it easily depolymerize, therefore, the NBO/T index for the Ca12Al14O33 phase becomes irrelevant. Furthermore, the morphology and size evolution of the obtained residue measured with laser particle analyzer indicates the agglomeration behavior of the residue particles during the leaching process.
       
  • Precious metals recovery from waste printed circuit boards using
           thiosulfate leaching and ion exchange resin
    • Abstract: Publication date: Available online 19 March 2019Source: HydrometallurgyAuthor(s): Sebastián Gámez, Karla Garcés, Ernesto de la Torre, Alicia Guevara Precious metals recovery from secondary sources is a novel alternative since they hold higher contents of several metals than average ores. In this research gold and silver were recovered from Waste Printed Circuit Boards (WPCBs) with the use of ammonia-thiosulfate solutions and the MTA 5011 ion exchange resin. First, it was necessary to remove the excess of copper from WPCBs since it could be detrimental for precious metals dissolution during leaching with thiosulfate. Nitric acid was the best reagent for decreasing copper concentration within WPCBs from 27% to 1.5%. Then, precious metals were dissolved with ammonia-thiosulfate solutions during 6 h at room temperature. Since copper was still within WPCBs, there was no need to add copper salts in order to form the copper tetramine complex required for accelerating precious metals dissolution. MTA 5011 ion exchange resin was used for precious metals recovery from leachates. It was determined that at higher resin: solution ratios, gold and silver recovery on the resin increased whereas selectivity towards gold diminished. The 87% of the gold was recovered and only 29% of copper was adsorbed too. Afterwards, a pre-elution stage was performed with sodium thiosulfate for a selective elution of copper. The 83% of the copper was desorbed while 28% of gold was eluted as well. For precious metals elution, several reagents were tested and KSCN was the most efficient of all since it desorbed the 98% of gold and only the 15% of the remaining copper. A combined solution of NaCl and Na2SO3 was assessed as well since they can regenerate the resin during the elution process. Finally, electrodeposition was better with solutions coming from elution with NaCl and NaSO3 (82% of Au and 94% of Ag recovery on cathodes surface) compared to those from thiocyanate elution (62% of Au and 87% of Ag).
       
  • Selective silica gel free scandium extraction from Iron-depleted red mud
           slags by dry digestion
    • Abstract: Publication date: Available online 19 March 2019Source: HydrometallurgyAuthor(s): Gözde Alkan, Bengi Yagmurlu, Lars Gronen, Carsten Dittrich, Yiqian Ma, Srecko Stopic, Bernd Friedrich A combination of pyrometallurgical and hydrometallurgical processes showed promising results for the sustainable valorisation of red mud with selective iron recovery. However; high Si content in red mud and its slags produced by pyrometallurgical treatment for the Fe removal makes these secondary resources untreatable with conventional acid leaching routes due to the formation of silica gel. In this study, red mud and slags synthesized by electric arc furnace smelting, which contain both moderate and extensive SiO2, were exposed to dry digestion aiming selective Sc recovery with suppressed Ti and Si dissolution. Various additions of concentrated sulfuric acid were investigated to find out the optimum acid consumption for this process. A promising Sc leaching efficiency was found for acidic slag (~80%), where Ti dissolution was suppressed to
       
  • Preparation of phosphor-tungstic acids (H3PW12O40) by solvent extraction
           with 2-octanol
    • Abstract: Publication date: Available online 18 March 2019Source: HydrometallurgyAuthor(s): Yongli Li, Zhongwei Zhao For more than a hundred years, extraction with ethyl ether has been the most used method for synthetizing H3PW12O40. However, the use of ethyl ether as the extraction agent faced many problems, such as strict regulation by public safety and environment authorities, poor operating environment, significant dissolution loss, low yields (approximately 80%), and difficulty in realizing continuous production.To overcome these problems, a new extraction method has been proposed in this paper, which uses 2-octanol as the extraction agent and water as the stripping agent. Under optimal conditions (30% 2-octanol in kerosene, O:A = 1:1, 180 g/L H2SO4, 20 g/L H3PO4, 45 °C, and a contact time of 2 min), 90.2% of H3PW12O40 contained in the solution was extracted in a single stage; the loaded H3PW12O40 could then be stripped completely via 3-stage continuous countercurrent stripping by maintaining O:A = 5:1, 65 °C, and t = 5 min. Finally, the obtained strip liquor, containing more than 550 g/L H3PW12O40, was evaporated to obtain crystals, resulting in an increased recovery rate of 10%.Graphical abstractUnlabelled Image
       
  • Hydrometallurgical production of LiNi0.80Co0.15Al0.05O2 cathode material
           from high-grade nickel matte
    • Abstract: Publication date: Available online 18 March 2019Source: HydrometallurgyAuthor(s): Zhao Xi, Zhixing Wang, Guochun Yan, Huajun Guo, Xinhai Li, Qiyang Hu, Wenjie Peng, Jiexi Wang In this study, a material-oriented metallurgical strategy, which is of such characteristics as short process, energy conservation and cost saving, is proposed to treat high-grade nickel matte and simultaneously produce LiNi0.80Co0.15Al0.05O2 cathode material for lithium ion batteries. This process is mainly composed of four steps, which is oxidation roasting, two-stage leaching, purification and material synthesis. First, high-grade nickel matte is roasted to eliminate sulfur under air atmosphere. Then the roasted product is first leached to selectively remove 78.10% Cu with little Ni and Co extraction at atmospheric temperature under optimum conditions (25 °C, HCl 1.50 mol L−1, L/S 7.0, 30 min). After that, 96.23% Ni, 96.58% Cu and 84.18% Co are extracted in thermal leaching process under optimum conditions (70 °C, HCl 3.0 mol L−1, L/S 10.0, 120 min), leaving Fe, Zn and Ca in residue. The obtained lixivium is purified by solvent extraction method to adjust the mass ratio of Cu and Ni to the range that meets the requirement for preparation of cathode material. Finally, LiNi0.80Co0.15Al0.05O2 material is produced by spray pyrolysis and sintering. The electrochemical performance of the resulting material is comparable with that prepared from analytical reagents, indicating such process can realize the comprehensive utilization of high-grade nickel matte.
       
  • Oxidative dissolution of nickel matte in dilute sulfuric acid solutions
    • Abstract: Publication date: Available online 18 March 2019Source: HydrometallurgyAuthor(s): Mehmet Hakan Morcali, Leili Tafaghodi Khajavi, Serdar Aktas, David B. Dreisinger Nickel matte (Ni3S2) is the most common feedstock for producing nickel oxide and nickel metal in associated refineries. Nickel matte is produced from sulfide or laterite ores, and contains around 73 wt% nickel. This study investigated the dissolution parameters of nickel matte in dilute sulfuric acid media in the presence of air as oxidant with the goal of presenting a cost-effective process for leaching nickel matte. The dissolution experiments were carried out to examine the following effects: air flow rate, stirring speed, S/L ratio, acid concentration, reaction temperature, reaction time and the amount of ferrous sulfate added. Nickel extraction of 90% and cobalt extraction of 80% were achieved using dilute H2SO4 and sparging of air as a source of oxygen. To increase the dissolution percentage of the matte, ferrous sulfate addition was studied and the oxidation and reduction potential (ORP) was measured to investigate the effect of ferrous ions on nickel and cobalt recovery. The highest nickel dissolution percentage (95%) was observed with the initial addition of 1200 ppm Fe (II). Characterization of samples has been carried out with quantitative X-ray diffraction (XRD) and scanning electron microscopy, along with an energy dispersive system (SEM-EDS).
       
  • Recovery of gallium from strong acidic sulphate leach solutions of zinc
           refinery residues using a novel phosphate ester extractant
    • Abstract: Publication date: Available online 14 March 2019Source: HydrometallurgyAuthor(s): Kuifang Zhang, Zhiqiang Liu, Yi Liu, Hongyang Cao, Wei Zhu A novel phosphate ester extractant (H2R) was used to extract gallium directly from strong acidic sulphate leach solutions of zinc refinery residues. The results indicated that the application acidity of H2R significantly exceeded those of P507 and P204 (two commonly used phosphate esters), and could directly extract gallium from the solutions with relatively high acidity (20–120 g/L H2SO4). In batch tests, 98.54% of gallium was extracted from solutions containing 0.205 g/L gallium and 107.80 g/L H2SO4 in four-stage counter current extraction, by using an organic system consisting of 40% (v/v) H2R in sulfonated kerosene with an A/O ratio of 1:1 at laboratory temperature (27 ± 1 °C) for 10 min. Meanwhile, extractions of other metals (germanium, zinc, copper, arsenic, and cadmium) were negligible, except for that of iron. After scrubbing using 200 g/L H2SO4 at an A/O ratio of 1:1, 99.13% of gallium in the loaded organic was selectively stripped using 200 g/L H2SO4 solution via five-stage counter current stripping with an A/O ratio of 1:4 at 27 ± 1 °C for 10 min, followed by using 7 mol/L HCl solution to strip co-extracted iron for recycling. Over the whole process, 96.71% of gallium was recovered and enriched in the pure gallium sulphate strip liquor with a concentration of 0.793 g/L. The results of continuous running tests demonstrated that H2R could be used to selectively recover gallium from strong acidic sulphate leach solutions of zinc refinery residues, with high stability and good cycling performance.
       
  • Experimental investigation on the direct crystallization of high-purity
           AlCl3·6H2O from the AlCl3-NaCl-H2O(-HCl-C2H5OH) system
    • Abstract: Publication date: Available online 8 March 2019Source: HydrometallurgyAuthor(s): Huaigang Cheng, Lixiang Wu, Jianwei Zhang, Huibin Lv, Yanxia Guo, Fangqin Cheng Equilibrium and nonequilibrium phase diagrams of the AlCl3-NaCl-H2O(-HCl-C2H5OH) salt water system were drawn and these were used to optimize the separation technology for solving the problem of aluminum chloride hexahydrate extracted from hydrochloric acid leach liquor with low purity because of the contamination of sodium chloride. The phase diagram of the AlCl3-NaCl-H2O(-HCl-C2H5OH) system is a simple eutonic type. It is weakly dependent on temperature but is greatly affected by hydrochloric acid and ethanol. Acidity can nonselectively decrease the solubility of the two salts, and this leads to similar aluminum/sodium ratios in the co-saturated liquid phase with different acidities and temperatures. As a result, the obtained aluminum chloride hexahydrate has a maximum purity of 96.65%. Adding ethanol to the system can increase the differences in solubility and crystal size between the two salts. Thus, in accordance with the theoretical route of evaporation and ethanol-assisted re-dissolution, aluminum chloride hexahydrate crystals were precipitated with a higher purity of 99.50%.Graphical abstractUnlabelled Image
       
  • Processing anatase ores for pigment production
    • Abstract: Publication date: Available online 3 March 2019Source: HydrometallurgyAuthor(s): Keith R. Barnard, Robbie G. McDonald, Mark I. Pownceby, Graham J. Sparrow, Wensheng Zhang Compared with processing high-TiO2 concentrates such as ilmenite ores, processing an anatase ore to achieve impurity levels acceptable for pigment production is more difficult because of the extensive number of accessory minerals present, the significant intergrowths between minerals and the fact that impurity elements may be distributed in several different minerals. In this paper, conditions applicable to processing anatase ores are reviewed with an aim of identifying conditions that may produce a suitable feedstock for processing to titania pigment by either the sulphate or chloride routes.Anatase ores containing 25–35 wt% TiO2 currently are processed using mineral dressing techniques of crushing and grinding, classification, magnetic separation and flotation to produce a concentrate with around 65 wt% TiO2. This concentrate is then typically upgraded to over 90 wt% TiO2 using combinations of heating and leaching treatments, often with the addition of a fluxing reagent to assist in impurity removal. The suitability of these products as a feedstock for the sulphate and chloride routes to pigment is discussed.
       
  • Novel membrane percrystallisation process for nickel sulphate production
    • Abstract: Publication date: Available online 2 March 2019Source: HydrometallurgyAuthor(s): Rasmus S.K. Madsen, Julius Motuzas, Anne Julbe, James Vaughan, João C. Diniz da Costa This research reports on an investigation of the performance of inorganic membranes for use in the percrystallisation of nickel sulphate hydrate. In this novel process, the separation of the solvent (water) and the crystallised solute (nickel sulphate hydrate) occurs continuously in a single-step, avoiding further downstream processing (crystal filtering and drying). The inorganic membranes were synthesised with sucrose solution followed by a post vacuum-assisted impregnation of the coated film on a α-alumina substrate and carbonisation under nitrogen atmosphere. The highest fluxes measured were 22 L m−2 h−1 and 1 kg m−2 h−1 (40 g L−1) for water and nickel respectively. Interestingly, the transport of solution through the membrane also affected the hydration state of the nickel sulphate, as well as the crystal type and shape. High water fluxes delivered pure nickel sulphate heptahydrate with elongated and laminar crystal particles (~200 μm). Lower water fluxes produced both heptahydrate and hexahydrate salts with approximately spherical particles (also ~200 μm). There a number of factors that influence the crystallisation reaction such as the rate of evaporation which affects water availability and the resultant temperature at the permeate side of the membrane. Finally, the activation energy for nickel sulphate crystallisation was estimated to be approximately 16 kJ mol−1 based on feed solution temperatures.Graphical abstractUnlabelled Image
       
  • Understanding the role of natural clay minerals as effective adsorbents
           and alternative source of rare earth elements: Adsorption operative
           parameters
    • Abstract: Publication date: Available online 26 February 2019Source: HydrometallurgyAuthor(s): Aref Alshameri, Hongping He, Chen Xin, Jianxi Zhu, Wei Xinghu, Runliang Zhu, Hailong Wang To better understand the influence of structure and surface properties of NCMs towards REE, requires individual research for each NCM. The adsorption/extraction for light (La3+) and heavy (Yb3+) REE of kaolinite (Kao), montmorillonite (Mt), muscovite (Ms), illite (Ilt), were systematically investigated and compared. Additionally, all the NCMs were fully characterized by XRD, XRF, XPS, Zeta potential and nitrogen adsorption-desorption isotherms to build the relationship between adsorption/extraction mechanism and minerals' property. Our experiments show that the Mt. exhibits highest adsorption and regeneration efficiencies for both La3+ and Yb3+ and decrease in the order of Mt > Ms > Ilt > Kao, while Kao has highest extractions efficiencies for both REE in the order of Kao > Ilt > Mt > Ms 89% for La3+ and 85% for Yb3+ were achieved from Kao and the lowest extractions were obtained from Ms. (63% for La3+ and 57% for Yb3+). The lack of Ms. on both reuse and extraction characteristics is believed to be related to presence of iron oxide associated with Ms. In addition, the important role of the pH in extraction of REE from NCMs was evidenced, when REE-NCMs come into contact with the NH4+ solution, the pH is rapidly increased over initial pH solution for both Mt. and Ms., thus leading to the decrease of the availability of ion-exchangeable REE with NH4+ions. The results illustrated that the structure and surface properties of NCMs are also the key factors that affect the rare earth leaching, thus identifying the types of NCMs and associated impurities in clay materials are important, either for getting the best leaching system or in developing a new one.Graphical abstractUnlabelled Image
       
  • Dual aeration tests with heap leaching of a pyrrhotite-rich pentlandite
           ore
    • Abstract: Publication date: Available online 26 February 2019Source: HydrometallurgyAuthor(s): Antti Arpalahti, Mari Lundström A large-scale investigation into the effect of increased aeration on heap leaching of a pyrrhotite-rich pentlandite ore was commenced at the Terrafame mine in Finland. The typical reference air feed amount in operation is approximately 0.05 m3/metric ton/h, fed from one direction of the 330 to 350 m wide heap. In the current study approximately 62% higher air feed vs. reference operation was trialed by installing another layer of aeration from the opposite direction of the heap. The hypothesis was that air distribution across the ore would be improved and that the increase in air feed would result in faster oxidation of pyrrhotite, leading ultimately to improved recovery of valuable metals. The heaps were observed for 150 days after stacking. The results revealed an increase in the leaching rates of several metals: manganese, magnesium, iron, nickel and zinc leached 14, 171, 142, 1932, and 1309% more in the presence of extra aeration during the observation period. In addition, applying the extra air showed a 324% increase in the generation of acid within the heap.
       
  • Response surface modeling for lab-scale column bioleaching of low-grade
           uranium ore using a new isolated strain of Acidithiobacillus Ferridurans
    • Abstract: Publication date: Available online 26 February 2019Source: HydrometallurgyAuthor(s): F. Jalali, J. Fakhari, A. Zolfaghari The microbial-assisted dissolution of minerals from low-grade ore resources has been recently developed into interesting processes to recover valuable metals, because of limitation in high- grade ore resources.In the present study, lab-scale column bioleaching of low-grade uranium ore by a new isolated strain of chemolithotrophic Acidithiobacillus Ferridurans, SBU-SH2 KY497231, which is isolated from a sulfur hot spring in Ardabil, NW of Iran, is investigated. Influence of bioleaching parameters is evaluated by setting up continues column experiments and using uranium samples provided from Sghand uranium mine, Yazd, central Iran. Furthermore, response surface methodology is used for statistical optimization of uranium recovery rate and its compliance with empirical results is examined. The statistical results show maximum 95.5% uranium extraction is obtained during 26 days at pH = 2.5, the temperature of 35 °C, at particle size of 4.64 mm, aeration and irrigation rate 0.78 ml/cm2/min and 1.03 ml/cm2/min respectively which are confirmed by experimental results.Analysis of experimental data by a statistical mathematical model indicates the most key factors on column uranium bioleaching are aeration and irrigation rate respectively. Maximum uranium recovery from leaching of control solution without bacterial cells is 11.33% which shows the isolated bacterium has a considerable influence on uranium recovery. In comparison to the other research reporters of column uranium bioleaching, the new strain of Acidithiobacillus Ferridurans, SBU-SH2, KY497231, indicates its salient features.
       
  • Novel and green metallurgical technique of selective recovery of lead from
           galena-sphalerite by electro-oxidation
    • Abstract: Publication date: Available online 26 February 2019Source: HydrometallurgyAuthor(s): Jinyong Tan, Zhan-fang Cao, Shuai Wang, Hong Zhong It is difficult to selectively obtain the qualified lead and zinc from the galena-sphalerite ore by using the existing pyrometallurgical process. A novel method by using electro-oxidation in Fe ion solution has been identified which facilitates the selective separation of lead from the galena-sphalerite concentrate. Fe was used as the leaching catalyst. The leaching process of galena and sphalerite has been systematically investigated. Adding galena-sphalerite to the solution, over 89.2% lead extraction has been demonstrated with
       
  • Microfluidic study of sustainable gold leaching using glycine solution
    • Abstract: Publication date: Available online 25 February 2019Source: HydrometallurgyAuthor(s): M.R. Azadi, A. Karrech, M. Elchalakani, M. Attar The purpose of this paper is to investigate the in-situ leaching of gold using a microfluidic system with controlled flow, temperature and fluid composition. The microfluidic system is a microchannel embedding a nano-scale layer of gold over which the fluid can flow and etch (erode) gold at various temperatures and concentrations of lixiviant. The lixiviant in this case is an alkaline glycine system that has been identified as an environmentally friendly substance to dissolve precious metals, it is used to extract gold within the engineered micro-cavity. As the fluid flows in the microchannel, the thickness of the gold layer is monitored to control its reduction with respect to time and space. The experimental conditions were varied to evaluate their effects on the recovery rate. The results show that compared to traditional methods being used in laboratory testing, this technique can provide real time measurements with low consumption of chemicals and the results can be obtained in shorter periods of time.
       
  • Improvement of Scorodite stability by addition of crystalline Polyferric
           Sulfate
    • Abstract: Publication date: Available online 25 February 2019Source: HydrometallurgyAuthor(s): Pingchao Ke, Kezhou Song, Ahmand Ghahreman, Zhihong Liu The stability of scorodite and scorodite with crystalline polyferric sulfate (PFS) added was investigated using the Toxicity Characteristic Leaching Procedure (TCLP) and leaching tests using NaOH solutions. The leaching behaviors of iron and arsenic were analyzed using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results indicated that the addition of PFS reduced the concentration of arsenic dissolved into the leaching solution significantly from 10 to 30 mg/L to below 0.01 mg/L through its adsorption and effect on the equilibrium of scorodite dissolution. The PFS addition facilitated the leaching of iron from the scorodite to precipitate as two-line ferrihydrite that coated the surface of scorodite particles. This potentially slowed down the diffusion of arsenic from the scorodite to the leaching solution. The thermodynamic calculations for the scorodite dissolution process showed that the formation/addition of ferrihydrite was effective in controlling the equilibrium arsenic concentration. With consideration of the ferrihydrite formation in the calculations, the scorodite was shown to be stable between pH 2.0–8.8, which was a wider range than the scorodite stability range of pH 2.0–5.8.
       
  • Energy-efficient and simultaneous extraction of lithium, rubidium and
           cesium from lepidolite concentrate via sulfuric acid baking and water
           leaching
    • Abstract: Publication date: Available online 23 February 2019Source: HydrometallurgyAuthor(s): Xiufeng Zhang, Xiumin Tan, Chun Li, Yuejun Yi, Weizao Liu, Lizhen Zhang Lepidolite is a valuable mineral resources of lithium, rubidium and cesium. However, most researches only focused on the lithium extraction without recovery of rubidium and cesium, and most of these processes involved energy-intensive high-temperature roasting and/or mechanical activation. In this study, simultaneous extractions of lithium, rubidium and cesium from a lepidolite concentrate were conducted through a low-temperature sulfuric acid baking and water leaching route. The influence of the extraction process parameters were systematically investigated. An optimized baking and leaching condition was determined as follows: H2SO4 concentration 85 wt%, baking temperature 200 °C, acid-to-concentrate mass ratio 1.7:1, baking time 4 h, 88% concentrate particles
       
  • Recovery of molybdenum and rhenium in scrub liquors of fumes and dusts
           from roasting molybdenite concentrates
    • Abstract: Publication date: Available online 22 February 2019Source: HydrometallurgyAuthor(s): Hossein Salehi, Hamed Tavakoli, M.R. Aboutalebi, H.R. Samim The present work addresses the recovery of rhenium from scrub liquor of molybdenite concentrate roasting fume and dust by solvent extraction method. According to the results, recovery of rhenium from the scrub liquor is not practical unless molybdenum is removed in advance. The extraction of molybdenum was carried out using a D2EHPA-TBP system which resulted in up to 99.8% Mo extraction in a two-stage solvent extraction at pH = 1 and O/A = 1. Up to 99.6% of Re was extracted subsequently using TOA in a single-stage extraction at pH = −0.3 and O/A = 1:20. The organic phase was stripped by ammonium hydroxide 32% and the resultant liquor was further subjected to evaporation as a result of which, an enriched purified solution was obtained. Ammonium perrhenate was precipitated from the enriched liquor by adjusting the pH to 6.5–7.
       
  • Grafting of organic sulfur-containing functional groups on activated
           carbon for gold(I) adsorption from thiosulfate solution
    • Abstract: Publication date: May 2019Source: Hydrometallurgy, Volume 185Author(s): Yunlong Chen, Futing Zi, Xianzhi Hu, Hong Yu, Yanhe Nie, Peng Yang, Huiling Cheng, Qiang Wang, Xuecong Qin, Shuliang Chen, Yan Zhang In the present study, sulfur-containing functional groups were grafted onto activated carbon and adsorption behavior for [Au(S2O3)2]3− was studied. Activated carbon grafted with sulfur-containing functional groups (S-AC) was developed with MBT (2-Mercaptobenzothiazole). The effects of MBT dosage and contact time in the preparation process were optimized; solution pH, thiosulfate ion concentration, and temperature of the surroundings in the adsorption stage over gold adsorption were studied. With a contact time of 24 h and MBT dosage of 0.7 g, S-AC had better gold adsorption ability and the prepared adsorbents worked well at a pH of about 9.0 and thiosulfate concentration of about 0.1 mol/L. The Freundlich model and pseudo-second order kinetics model fit the [Au(S2O3)2]3− adsorption process well. A total gold amount of 18.402 kg/t for five stages was attained with S-AC. The presence of thiol and disulfide linkages on the surface of activated carbon was proved using XPS, FT-IR, BET, and SEM. The adsorption of [Au(S2O3)2]3− onto S-AC involved a gold(I) thiolate and disulfide interchange mechanism. This study made the adsorption of [Au(S2O3)2]3− on activated carbon possible via a simple and feasible method, and this is of great significance for future research in leaching gold with thiosulfate.Graphical abstractUnlabelled Image
       
  • Hydrometallurgical preparation of lithium carbonate from lithium-rich
           electrolyte
    • Abstract: Publication date: May 2019Source: Hydrometallurgy, Volume 185Author(s): Wei Wang, Weijie Chen, Haitao Liu Recovery of lithium from lithium-rich electrolytes has attracted worldwide attention because of issues related to the electrolytic production of aluminum and its environmental impacts. Lithium carbonate preparation from a lithium-rich electrolyte by H2SO4 leaching, followed by removal of impurities and lithium precipitation with Na2CO3 was investigated. About 98% Li leaching efficiency was achieved in 1 h using 6% H2SO4 at 80 °C while maintaining a liquid-to- solid ratio of 2:1. Li2SO4 in the resulting leach solution was sequentially purified by NaOH addition to an end pH of 11 and then addition of 3 g/L ethylenediaminetetraacetic acid. Li2CO3 of 99.5% purity was then obtained by precipitation with addition of 290 g/L Na2CO3 at 95 °C for 50 min. This research is expected to improve understanding of requirements for the stable operation of electrolytic aluminum production and to potentially design processes for recycling of industrial lithium-rich electrolytes with high viability.
       
  • Separation of scandium from the other rare earth elements with a novel
           macro-porous silica-polymer based adsorbent HDEHP/SiO2-P
    • Abstract: Publication date: Available online 18 February 2019Source: HydrometallurgyAuthor(s): Wei Zhang, Shuqi Yu, Shichang Zhang, Jie Zhou, Shunyan Ning, Xinpeng Wang, Yuezhou Wei A novel macro-porous silica-polymer (SiO2-P) based di(2-ethylhexyl) phosphonate adsorbent (HDEHP/SiO2-P) was synthesized by vacuum impregnation method for separating Sc from the other rare earth elements (REEs). The as-prepared HDEHP/SiO2-P exhibited excellent selectivity towards Sc (III) over the other REEs(III) with SFSc/M over 50 in 0.1–5 M H2SO4 solutions. The adsorption was spontaneous and endothermic with the capacity of 14.1, 14.8, 15.5 mg Sc/g in 5 M H2SO4 solution at 298 K, 308 K, 318 K, respectively. The adsorption equilibrium was obtained within 5 min. Moreover, the FT-IR, XPS analysis and IC test suggested that the adsorption mechanism of Sc(III) performed through ion exchange at low acidity (≤0.5 M H2SO4) while the solvation effect by sharing the electron pairs in the oxygen atoms from PO dominated at high acidity, which was very different from that of the other REEs such as Lu(III) whose adsorption mechanism is dominated by ion exchange at the experimental acidity (pH 2.39–4 M H2SO4). The relatively fast adsorption kinetics, high adsorption capacity and high selectivity of HDEHP/SiO2-P towards Sc(III) indicate its potential candidate for separating Sc(III) from the other REEs(III).Graphical abstractUnlabelled Image
       
  • Innovative technology for the production of high-purity sand silica by
           thermal treatment and acid leaching process
    • Abstract: Publication date: Available online 18 February 2019Source: HydrometallurgyAuthor(s): Marouan Khalifa, Rachid Ouertani, Messaoud Hajji, Hatem Ezzaouia The production of high purity silica out of natural sand plays a critical role as a starting material in the industry of glass and high grade silicon. In this paper, we expose a novel processing method for the purification of sand silica. This method is a subsequent combination of thermal treatment and acid leaching. Firstly, samples of Tunisian natural sand were submitted to a rapid thermal annealing in an infra-red furnace under O2 atmosphere at fixed temperature and time 1000 °C and 1 h, respectively. Subsequently, the samples were soaked in an aqueous acid solution composed hydrofluoric acid and a hydrochloric acid concentration. This last acid leaching step was intended to remove the gettered impurities during the annealing step. Various characterization techniques such as optical absorption, energy dispersive X-ray analysis, electronic paramagnetic resonance analysis and atomic absorption spectroscopy were used aiming to evaluate the effectiveness of this impurity gettering technology. The results show substantial reduction in all metallic impurities in silica after three successive purification cycles improving the purity from 99.7 to 99.9%.
       
  • The role of glycine in the ammonium thiocyanate leaching of gold
    • Abstract: Publication date: Available online 18 February 2019Source: HydrometallurgyAuthor(s): Wu Hao, Yali Feng, Wanfu Huang, Li Haoran, Shengde Liao Thiocyanate leaching is an efficient and environmentally friendly method to extract gold due to fast leaching speed, excellent reaction selectivity and slight environmental risks, but thiocyanate is easily oxidized to decompose by oxidant in the leaching process, resulting in large consumption of leaching agent. In this work, synergistic leaching experiments were carried out with a mixed reagent system of ammonium thiocyanate and glycine for exploring the role of glycine in thiocyanate leaching. And the theoretical mechanism of glycine in thiocyanate leaching was also investigated. The results showed that as glycine was added into the thiocyanate leaching solution, the decomposition reaction of thiocyanate would be lessened, resulting in lower ammonium thiocyanate consumption. Meanwhile, owing to its characteristic of gold dissolution, glycine can be used as an additional leaching agent to increase the gold leaching ratio. Optimized gold-extraction efficiency (93.15%) of gold-bearing flotation concentrate was achieved under the following conditions: a concentration of thiocyanate, glycine and oxidant Fe3+ at 0.6 mol/dm3, 5 g/dm3 and 0.05 mol/dm3, respectively; stirring speed at 600 rpm; pH at 2; temperature at 298 K; leaching time of 3 h and a liquid-solid ratio of 4:1.
       
  • Improving gold recovery from a refractory ore via Na2SO4 assisted roasting
           and alkaline Na2S leaching
    • Abstract: Publication date: Available online 17 February 2019Source: HydrometallurgyAuthor(s): Xiaoliang Liu, Qian Li, Yan Zhang, Tao Jiang, Yongbin Yang, Bin Xu, Yinghe He Gold recovery from refractory gold ores with controlled roasting remained well below 80%. Na2SO4 was added in an O2-enriched single stage roasting of a refractory gold ore to improve its gold recovery. Changes in physicochemical properties of the calcines suggested that this reduced the sintering as well as facilitated the formation of pores and a water soluble phase within the calcine. Thermodynamic analysis and leaching results demonstrated that Na2S solutions could effectively remove Sb species from the calcine. An extraction process that includes Na2SO4 assisted roasting and alkaline Na2S leaching is shown to be able to achieve a gold recovery of over 95% from the refractory ore.
       
  • Recovery of rare earth elements from coal fly ash using TEHDGA impregnated
           resin
    • Abstract: Publication date: Available online 16 February 2019Source: HydrometallurgyAuthor(s): S. Mondal, A. Ghar, A.K. Satpati, P. Sinharoy, D.K. Singh, J.N. Sharma, T. Sreenivas, V. Kain Coal fly ash samples from different power plants of India have been collected and studied for their rare earth content and recovery. These samples were dissolved in nitric acid by (1) acid-digestion method and (2) by fusion with NaOH + NaNO3 mixture at 600 °C followed by successive hydrothermal treatment of the fused mass. The analysis of major and trace elements was done by ICP-AES.All the samples have similar element distribution with total rare earth content found in the range of 300 to 500 mg/kg and major elements as silicon, aluminum, iron, calcium and magnesium. Separation of bulk of the rare earth from matrix elements were carried out by using TEHDGA (N,N,N′,N′-tetrakis-2-ethylhexyldiglycolamide) impregnated XAD-7 resin. Quantitative separation of rare earth was obtained with no uptake of major elements. Simulated solution containing La, Nd, Y and Er, representing lighter and heavier rare earth, was prepared and studied for their adsorption behavior. The adsorption isotherm fitted well with Langmuir modelindicating monolayer adsorption of rare earth elements. Desorption of loaded rare earth elements was achieved by elution with 0.01 M nitric acid solution. The resin was recycled for 10 times and found to retain its extraction and elution properties.
       
  • An environmentally friendly hydrothermal method of vanadium precipitation
           with the application of oxalic acid
    • Abstract: Publication date: Available online 12 February 2019Source: HydrometallurgyAuthor(s): Qian Kang, Yimin Zhang, Shenxu Bao During the traditional metallurgical process of vanadium (V), an ammonium salt is often employed as the precipitator to form an ammonium vanadate, which converted into V2O5 in the subsequent calcination. Due to the restriction of ammonia emissions by the Chinese government, the vanadium-bearing shale industry in China urgently needs to find out a new environmentally friendly vanadium precipitation method. As the widely used method in the synthesis of VO2, hydrothermal reduction with oxalic acid was firstly introduced into vanadium precipitation in this study. Several factors that affect the vanadium precipitation were studied in the batch tests, such as initial reaction pH, temperature, time, and n(H2C2O4·2H2O)/n(V(V)). A product with 99.53% purity of VO2(B) and 99.47% extent of vanadium precipitation was obtained under the optimized reaction conditions: initial reaction pH of 0.80, time of 8 h, temperature of 493 K, and n(H2C2O4·2H2O)/n(V(V)) of 1.00. Raman spectroscopy, inductively coupled plasma with optical emission spectrometry (ICP-OES) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were also carried out to characterize the product and the results indicated that the product was pure VO2(B) in the form of nanorods. The reaction mechanism of VO2 prepared from stripped vanadium solution is put forward and the transformation of V from stripped vanadium solution to VO2 is proposed as: VO2+ → VO2(C2O4)− → VOC2O4 → VO2. Overall, the present hydrothermal method of vanadium precipitation with the application of oxalic acid has the characteristics of environmentally friendly, short process, simple and efficient.
       
  • Effect of sulfide mineral content in copper-zinc concentrates on the rate
           of leaching of non-ferrous metals by biogenic ferric iron
    • Abstract: Publication date: Available online 7 February 2019Source: HydrometallurgyAuthor(s): Natalya V. Fomchenko, Maxim I. Muravyov The leaching of copper-zinc concentrates with different sulfide mineral content by biogenic ferric iron has been studied. It was determined that chalcopyrite, sphalerite, pyrrhotite, and pyrite were in the range of 29.0–55.2, 11.0–3.9, 33.5–14.4, and 12.1–12.8%, respectively. The rate of copper leaching was shown to decrease from 5.1 to 2.6 g/L/h, while its content in the concentrate decreased from 19.2 to 10.1%. The rate of zinc leaching increased from 2.9 to 5.3 g/L/h, while its content in these concentrates increased from 2.6 to 7.4%. The results indicate that the specific rates of copper leaching remained unchanged in all the concentrates studied and were within 0.2 and 0.27 g/g/h. We suggest that this was primarily associated with the dependence of this parameter on the rest potential of chalcopyrite. The specific rate of zinc leaching varied from 0.73 to 1.14 g/g/h and depended significantly on the ratio of contents of sulfide minerals in the concentrates. This rate was also found to increase with an increase in the chalcopyrite content in the concentrate, which indicated the presence of galvanic interactions between the minerals. At the same time, sphalerite and pyrrhotite, which are the minerals with a low rest potential, acted as dissolving anodes, while chalcopyrite and pyrite, having high rest potentials, were cathodes. The possibility of predicting the efficiency of zinc and iron removal during ferric leaching of the copper-zinc concentrates was shown in the context of sulfide mineral content.
       
  • Recovery of Ga(III) from chloride solutions by solvent extraction with
           Cextrant 230
    • Abstract: Publication date: Available online 3 February 2019Source: HydrometallurgyAuthor(s): Xueke Zhou, Zhifeng Zhang, Shengting Kuang, Yanling Li, Yuqin Ma, Yunhui Li, Wuping Liao In the present work, an α-aminophosphonate extractant di(2-ethylhexyl) [N-(2-ethylhexyl)aminomethyl] phosphonate (Cextrant 230, L) was applied for the selective extraction and recovery of Ga(III) from the chloride solutions. The extraction of Ga(III) was compared with that of other metal ions such as Fe3+, Fe2+, Zn2+, Al3+, Mg2+ and Sn2+. The extracted complex of Ga(III) was deduced to be HGaCl4·L. The extraction equilibrium constant and thermodynamic parameters (ΔG, ΔH and ΔS) were calculated. The positive value of ΔH indicates that the extraction reaction of Ga(III) is an endothermic process. The loading capacity of 30% (v/v) Cextrant 230 for Ga(III) was determined to be 0.38 mol/L. The loaded gallium can be complete stripped by distilled water. A process was established for the selective recovery of Ga(III), by which the purity of the gallium product reached 94% with a yield of 89.5%
       
  • Ultrasound and Microwave assisted leaching of neodymium from waste magnet
           using organic solvent
    • Abstract: Publication date: Available online 3 February 2019Source: HydrometallurgyAuthor(s): S.S. Behera, Subhendu K. Panda, D. Mandal, P.K. Parhi Application of ultrasound and microwave assisted technology on the dissolution of neodymium (Nd) from waste magnet using organic reagent (s) was investigated. Amongst all the organic solvents, acetic acid appears to be effective while yielding higher Nd leaching efficiency. The characteristics pattern of XRD and SEM-EDAX study ascertained the magnet waste phase as Nd-Fe-B. Factors influencing the leaching of Nd such as time (0-5 h), [CH3COOH] (0.1–0.5 M), ultrasound power (0 W–120 W), pulp density(S/L) (1–5%) and microwave power (450-900 W) have been studied. Quantitative (~99.99%) Nd recovery was achieved under optimum ultrasound assisted leaching condition; time: 120 min, ultrasound power: 90 W, [CH3COOH]: 0.4 mol/L and particle size range: 75–106 μm. Almost all Nd dissolution was attained at the suitable MW power of 900 W leading to reduce leaching time by 120 min than the regular mechanical stirring leaching (65.03% Nd resulted in 240 min). The enhancement of Nd leaching was mainly due to unique cavitation action of ultrasoundation and high heating energy produced from microwave to break the solid matrix of waste magnet, leading to diffuse the Nd metal ion into lixivaint phase as ascertained from SEM results of the magnet waste sample before and after ultrasound wave / microwave treatment.Graphical abstractUnlabelled Image
       
  • Reviews the research on some dimensionally stable anodes (DSA) based on
           titanium
    • Abstract: Publication date: Available online 30 January 2019Source: HydrometallurgyAuthor(s): Vesna Krstić, Branka Pešovski The metal mixed oxides (MMO) such as RuO2, IrO2, TiO2 as excellent catalysts on the surface of dimensionally stable anodes (DSAs) preparing by aqueous solutions of platinum-group metals (PGMs) chlorides for the copper electrolysis has been discussed. One of the possible surface modifications of the new titanium DSAs could be the alloying of the PGMs at low temperatures. This possibility has been described using the synthesis of catalysts for the reaction of crotonaldehyde hydrogenation and their characterization. The discussed results are related to the increase of current density by using alternative types of anodes and charge transfer between specific PGMs as well as chemical reaction engineering, and surface acidity in the catalysts.Graphical abstractUnlabelled Image
       
  • Extraction of lithium from wastewaters using a synergistic solvent
           extraction system consisting of Mextral EOL and Cyanex 923
    • Abstract: Publication date: Available online 29 January 2019Source: HydrometallurgyAuthor(s): E. Ender Çelebi, M. Salim Öncel, Mehmet Kobya, Mahmut Bayramoğlu A process-controlled synergistic solvent extraction (SSX) system consisting Mextral EOL (β-diketone derivative) and Cyanex 923 (mixture of four alkyl phosphine oxides) has been developed for the extraction of lithium from borate and sodium rich wastewaters induced by boron industry. In order to determine regression models and determine optimum conditions, a D-optimal experimental plan was created. Reduced cubic models were chosen for all lithium and sodium extraction studies. Accordingly, the most negative effect in lithium extraction was the aqueous phase/organic phase ratio (A/O), while the pH was the most positively effective parameter. Mextral EOL had no effect on sodium extraction. Notably, it was found that Mextral EOL and Cyanex 923 had up to 1.6 times synergistic effect on lithium extraction. In optimization, the sodium extraction efficiency is minimized while the lithium yield is maximized. Three different optimization criteria were determined in each wastewater and three different optimum alternatives were established. Accordingly, the highest lithium yield was predicted to be above 91.0% and sodium yield was below 4.70%. In back-extraction studies, water and different concentrations of HCl acid solutions were used as scrubbing and stripping agents. As a result, the Mextral EOL/Cyanex 923/Kerosene SSX system has been proven to be an effective method for maximizing lithium extraction from borate-rich wastewaters and for minimizing sodium extraction.
       
  • Recovery and separation of silver and mercury from hazardous zinc refinery
           residues produced by zinc oxygen pressure leaching
    • Abstract: Publication date: Available online 26 January 2019Source: HydrometallurgyAuthor(s): Fupeng Liu, Jinliang Wang, Chao Peng, Zhihong Liu, Benjamin P. Wilson, Mari Lundström Hazardous zinc refinery residues that contain Ag and Hg are a typical complex material obtained from zinc oxygen pressure leaching and currently there are few economically viable methods for disposal or reuse. The research presented here offers an effective approach for the comprehensive recovery of Zn, Fe, Cu, Ag and Hg from this highly toxic waste. During the initial hot-acid leaching stage, leaching efficiencies of 96.3% Zn, 96.0% Fe and 97.5% Cu were obtained, whereas the leaching of Ag and Hg were
       
  • Recovery of nitric and acetic acids from etching waste solutions using a
           synergistic system consisting of N235 and TRPO in cyclohexane
    • Abstract: Publication date: Available online 26 January 2019Source: HydrometallurgyAuthor(s): Ye Wang, Fang Chen, Xiaodong Ma, Guoquan Zhang To purify and recover phosphoric acid (H3PO4) from laboratory synthetic etching waste, Alamine 336 (N235) and trialkyl phosphine oxide (TRPO) were used in a mixed extractant to extract nitric (HNO3) and acetic acids (HAc). The effects of the extraction temperature, extractant concentration, and ratio of the organic phase to the liquid phase on the separation process were investigated. Using an organic system containing 3.5% (v/v) N235, 46.5% (v/v) TRPO, and 50% (v/v) cyclohexane, 70% of the HAc and 85% of the HNO3 were extracted, with 8.5% H3PO4 co-extracted through single-stage contact. Furthermore, more than 99% HAc and 99.5% HNO3 were removed after three counter-current extractions, with only ~15% of the H3PO4 being co-extracted. A stripping rate of more than 99% was achieved for HNO3, HAc, and H3PO4 using 0.25 mol·L−1 NH3·H2O. UV–vis and FT-IR analyses indicated that the N235 and TRPO mixture had a synergistic effect on HNO3 and HAc extraction. The mechanisms of HNO3 and HAc extraction involve ion-pair association and hydrogen bonding, respectively.
       
  • Separation of Re(VII) from Mo(VI) by anion exchange resins synthesized
           using microwave heat
    • Abstract: Publication date: Available online 24 January 2019Source: HydrometallurgyAuthor(s): Piotr Cyganowski, Agata Cierlik, Anna Leśniewicz, Paweł Pohl, Dorota Jermakowicz-Bartkowiak A microwave-assisted method for the synthesis of Re(VII)-selective anion exchange resins is proposed within this paper. The procedure involved (1) the copolymerization of vinylbenzyl chloride (VBC) and divinylbenzene (DVB), followed by (2) the modification thereof using 1-(3-aminopropyl)imidazole. Synthesis was carried out by applying different sets of microwave heating. Then, samples based on VBC-co-DVB copolymer, obtained conventionally or under exposure to microwaves, were applied by adsorbing ReO4− ions from solutions acidified at 0.1 M HCl containing oxoanions of Re(VII), Mo(VI) and V(V), as well as Cu(II). The studies covered adsorption behavior at equilibrium and the selective properties of the prepared resins.The maximum Re(VII) adsorption capacity of 303 mg g−1 was achieved by the resin, and was obtained under constant exposure to microwaves at each stage of the synthesis procedure. All the resins selectively separated Re(VII) from Mo(VI). Selectivity of the adsorption towards ReO4− ions was up to 200-fold greater when compared to the 6-fold molar excess of Mo(VI) ions.Terms and symbols.CeEquilibrium solute concentration (mg dm−3)DVBDivinylbenzeneKDPartition coefficient, mL g−1KfFreundlich constantKLLangmuir constant (L mg−1)nFreundlich parameter, dimensionlessQ0Monolayer capacity (mg g resin)qeEquilibrium adsorption capacity (mg g−1)R2Correlation coefficientRLSeparation factor, dimensionlessSStyrenesiSelectivity index, dimensionlessVBCVinylbenzyl chlorideGraphical abstractUnlabelled Image
       
  • Investigation of alumina preparation from aluminum chloride aqueous
           solution by electrical transformation
    • Abstract: Publication date: Available online 23 January 2019Source: HydrometallurgyAuthor(s): Xiuxiu Han, Ting-an Zhang, Guozhi Lv, Xijuan Pan, Daxue Fu High-alumina fly ash is an alumina-rich mineral resource that can potentially replace low-grade bauxite. While a wide range of different traditional processes are available for extracting alumina from high-alumina fly ash, these processes have many disadvantages. Northeastern University has recently proposed a new electrotransformation processing technique for transforming AlCl3 into Al2O3 in the process of extracting Al2O3 from high-alumina fly ash by the hydrochloric acid method. The feasibility of this new electrotransformation method was studied in this paper. The effects of the current intensity, electrotransformation time, initial electrotransformation temperature and initial HCl concentration on the electrotransformation process and roasting products were investigated. The results show that the pH of the electrolyte increases with increasing current strength, electrolytic time, initial electrotransformation temperature and HCl initial concentration, and its value tends to be 3.2. Under these conditions, XRD and SEM examinations confirm that the roasting products are Al2O3 sheets with a cubic crystal system. An examination of the grain size shows that the grain sizes are uniform. Elemental content examinations show that the Cl contents of the obtained products are
       
  • Characterization, modeling, and optimization of a single-step process for
           leaching metallic ions from LiNi1/3Co1/3Mn1/3O2 cathodes for the recycling
           of spent lithium-ion batteries
    • Abstract: Publication date: Available online 23 January 2019Source: HydrometallurgyAuthor(s): Qian Cheng, William M. Chirdon, Meiduan Lin, Kuber Mishra, Xiaodong Zhou This work is focused on modeling and optimization of a single-step process for simultaneous leaching of Li, Ni, Co, and Mn from LiNi1/3Co1/3Mn1/3O2 cathodes for the recycling of spent lithium-ion batteries (LIBs). The response surface methodology based on a central composite face-centered design was used to comprehend the effect of the process parameters on the leaching efficiency of metallic ions. Characterization by X-ray diffraction and scanning electron microscopy confirmed the leaching process of spent cathode material was effective. The operating parameters investigated include H2SO4 concentration, H2O2 concentration, and the solid-to-liquid ratio. The leaching efficiency of Li was highly dependent on these independent parameters, while interactions between process parameters were found to significantly affect the leaching efficiencies of Ni, Co, and Mn. 80.2%, 91.5%, 93.2% and 90.3% of the Li, Ni, Co, and Mn, respectively, can be simultaneously recovered from the spent cathode materials considering the economics under optimal conditions. The optimal process could provide an alternative way for the recovery of metals from spent LIBs in industry for considering recycling cost and economic profitability.
       
  • Biosynthesis of iron oxide nanoparticles from mineral coal tailings in a
           stirred tank reactor
    • Abstract: Publication date: Available online 23 January 2019Source: HydrometallurgyAuthor(s): Danielle Maass, Alexsandra Valério, Luís Antonio Lourenço, Débora de Oliveira, Dachamir Hotza Chemical oxidation of mineral coal tailings is one of the most important environmental issues during the lifetime of a mine. The presence of sulfur compounds favors the occurrence of metal acid leaching, which contaminates water with bioaccumulative metals, rendering it unsuitable for domestic and agricultural use. The biomining of residual iron present in these tailings and its transformation into high added-value by-products is economically and environmentally attractive. The extraction of residual iron from rhomboclase and its transformation into nanoparticles by Rhodococcus erythropolis ATCC 4277 free-cells in a stirred tank reactor was studied. R. erythropolis ATCC 4277 biomining capacity was improved by diminishing stirring rate and oxygen flow rate of stirred tank reactor. According to the results of the 22 full factorial design, smaller sizes of iron-based nanoparticles (
       
  • Recovery of potassium hydroxide from strong potassium aluminate solutions
           using solvent extraction with alkyl phenols
    • Abstract: Publication date: Available online 23 January 2019Source: HydrometallurgyAuthor(s): Jin Xue, Cheng-Lin Liu, Meng-Jie Luo, Yong-Xing Bao, You-Fa Jiang, Sohrab Rohani, Ping Li, Jian-Guo Yu Solvent extraction of potassium hydroxide from strong potassium aluminate solutions was investigated systematically, where alkyl phenols with the stereo-hindrance of alkyl substituents to the hydroxyl functional group were used as extractants. The research focused on organic phase, phase equilibrium, multi-stage counter current extraction/stripping and extraction mechanism. The alkyl phenol, namely 2,4-di-tert-butylphenol, was found to be a promising extractant. When it was dissolved in 1-octanol diluent to form an organic phase, this organic phase would have a higher K/Al selectivity and a good stability for KOH extraction from the strong potassium aluminate solution. The extraction mechanism of KOH by alkyl phenol was analyzed and found to agree with the so-called pseudo-hydroxide extraction mechanism. The phase equilibrium curves in both KOH-H2O-organic phase system and KOH-KAlO2-H2O-organic phase system were measured at different temperatures with different extractant concentrations. Based on the measured phase equilibrium data, a multi-stage counter current extraction/stripping process was designed, and experiments by single-stage, two-stage and three-stage processes were carried out to evaluate the feasibility and efficiency of the KOH extraction from the strong alkaline potassium aluminate solutions. Through a three-stage extraction process at 40 °C, KOH concentration in potassium aluminate solution with 3.7 mol/L Al can be decreased from 528 g/L to 312 g/L, satisfying the Al(OH)3 seeded precipitation condition.
       
  • A bio-hydrometallurgical approach towards leaching of lanthanum from the
           spent fluid catalytic cracking catalyst using Aspergillus niger
    • Abstract: Publication date: Available online 23 January 2019Source: HydrometallurgyAuthor(s): H.M. Mouna, Saroj Sundar Baral Spent fluid catalytic cracking catalysts (SFCCC) are the wastes generated from oil refineries, which accounts for 700,000–900,000 metric ton/year worldwide. Lanthanum, a short-term near critical element is the key component of SFCCC and accounts for 8170 mg/Kg. The current research intends to recover lanthanum from SFCCC by Aspergillus niger and compare the results with strong organic and inorganic acid leaching. Batch studies of one-step bioleaching (OSB) at 1, 3 and 5% pulp densities yielded 63%, 52%, and 33% lanthanum recovery, respectively. The decrease in leaching efficiency with an increase in pulp density may be attributed to the inhibition effect of SFCCC on A. niger. Citric acid was the main lixiviant produced by A. niger, whose production was triggered by SFCCC at ≤1% pulp density. Acidic pH of the leaching medium suggested acidolysis as the key mechanism. Cell-free spent medium bioleaching (cfSMB) resulted in 30.8% leaching recovery, which was significantly less than the OSB. In chemical leaching, sulfuric and nitric acid showed 38% efficiency whereas oxalic acid showed 5% recovery. Hydrochloric, citric and gluconic acids resulted in 68%, 65%, and 64% leaching recoveries, respectively, which is nearly the same as that offered by OSB. OSB being the greener process, suggested for lanthanum leaching from SFCCC over other processes.
       
  • A novel process on separation of manganese from calcium and magnesium
           using synergistic solvent extraction system
    • Abstract: Publication date: Available online 23 January 2019Source: HydrometallurgyAuthor(s): Yingsong Wang, Li Zeng, Guiqing Zhang, Wenjuan Guan, Zhen Sun, Dong Zhang, Jialin Qing The synergistic solvent extraction (SSX) system consisting of di-2-ethylhexyl phosphoric acid (P204) and alkyl-4-pyridinecarboxylate ester (4PC) in sulfonated kerosene was used to separate manganese from magnesium and calcium and to prepare pure manganese sulfate solutions with battery grade. In batch tests, over 99.9% of Mn2+ was extracted after a four-stage counter current extraction using an organic solution consisting of 0.25 mol/L P204 and 0.5 mol/L 4PC in sulfonated kerosene and a feed containing 22 g/L Mn2+, 4 g/L Mg2+ and 0.1 g/L Ca2+ with an A/O ratio of 1:6 at 25 °C for 10 min, while extractions of magnesium and calcium were negligible. After scrubbing using 0.025 mol/L H2SO4 at an A/O ratio of 1:8, the loaded organic solution was stripped using 0.7 mol/L H2SO4 at an A/O ratio of 1:8 to prepare pure manganese sulfate solutions with battery grade. The results of continuous operation test indicated that the mass ratios of Ca/Mn and Mg/Mn in strip liquors were below 5.6 × 10−5 and 2.5 × 10−4, respectively, further demonstrating the efficient separation of manganese from magnesium and calcium using the SSX system.
       
  • Interactions of iron and titanium-bearing minerals under high-temperature
           Bayer digestion conditions
    • Abstract: Publication date: Available online 18 January 2019Source: HydrometallurgyAuthor(s): Yi-lin Wang, Xiao-bin Li, Biao Wang, Qiu-sheng Zhou, Tian-gui Qi, Gui-hua Liu, Zhi-hong Peng, Ke-chao Zhou Clarifying the interactions among iron and titanium-bearing minerals in the treatment of diasporic bauxite with Bayer liquor at elevated temperature is crucial to understanding reductive Bayer digestion, in which the inhibition of sodium titanate on diaspore digestion is eliminated by the use of non-lime additive. In this work, we carried out a thermodynamic analysis, which predicted that ilmenite (FeTiO3), ulvite (Fe2TiO4), and sodium iron titanium oxide (NaFeTiO4) will result from the interactions among iron and titanium bearing minerals in Bayer digestion, whereas pseudobrookite (Fe2TiO5) cannot be generated. In addition, the perovskite (CaTiO3) is more stable than the produced Ti-Fe compounds, thus, the Ti-Fe compounds could be converted into this perovskite by the addition of extra lime. In order to confirm the thermodynamic analysis results, we then carried out both typical and reductive Bayer digestion experiments. Unlike the dense sodium titanate layer formed on the other minerals present in typical Bayer digestion, the fibrous porous sodium iron titanium oxide layer produced in reductive Bayer digestion allows the passage of the alkaline solution through the precipitated layer to the mineral particles beneath, and thus ensures the efficient digestion of the diaspore. The reaction of HFeO2− and titanium-bearing mineral to form Ti-Fe compounds occurs prior to the reaction of HFeO2− and hematite to form magnetite, meanwhile some of the insoluble Ti-Fe compounds have low iron content, therefore only a small amount of iron powder is needed to eliminate the inhibition. These results are important for the efficient digestion of diasporic bauxite through the addition of iron powder, which avoids the loss of alumina through the hydro-garnet produced by adding excess lime.
       
  • Selective rare earth element extraction using high-pressure acid leaching
           of slags arising from the smelting of bauxite residue
    • Abstract: Publication date: Available online 17 January 2019Source: HydrometallurgyAuthor(s): Rodolfo Marin Rivera, Buhle Xakalashe, Ghania Ounoughene, Koen Binnemans, Bernd Friedrich, Tom Van Gerven During acid leaching of bauxite residue (red mud), the increase in dissolution of rare-earth elements (REEs) is associated with a substantial co-dissolution of iron; this poses problems in the downstream processing (i.e. solvent extraction or ion exchange). Six different slags generated by reductive smelting of the same bauxite residue sample were treated by high-pressure acid leaching (HPAL) with HCl and H2SO4 to selectively extract REEs. Thus, up to 90 wt% of scandium was extracted from the slags using H2SO4 at 150 °C, while with HCl the extraction of scandium reached up to 80 wt% at120 °C. The extraction of yttrium, lanthanum and neodymium was above 95 wt% when HCl was used as a reagent, but it was much lower (90 wt%, 18 g L−1), while the concentration of the remaining iron (>60 wt%) was of3 g L−1 in the leachate. The co-dissolution of silicon and titanium was lower than 5 wt%.
       
  • Energy-efficient mineral carbonation of CaSO4 derived from wollastonite
           via a roasting-leaching route
    • Abstract: Publication date: Available online 11 January 2019Source: HydrometallurgyAuthor(s): Xingliang Xu, Weizao Liu, Guanrun Chu, Guoquan Zhang, Dongmei Luo, Hairong Yue, Bin Liang, Chun Li Mineral carbonation is an important technique for the sequestration of carbon dioxide (CO2) on a large scale. In this article, indirect carbonation of abundant wollastonite [CaSiO3] mineral combined with the use of a CO2 mineralization cell (CMC) for the recovery of mineralization energy has been proposed. The results of thermodynamic analysis reveal that the described process consumes 73% less energy than that required for the route, in which serpentine is utilized as the mineralization agent. During this process, calcium sulfate (CaSO4) was first derived with recyclable ammonium sulfate (AS) via a roasting-leaching route. The gaseous ammonia produced during the roasting stage was used to capture CO2 from a mixture of flue gases and simultaneously generate ammonium bicarbonate (NH4HCO3) and electricity by the CMC. The obtained NH4HCO3 solution reacted directly with the leaching slurry to mineralize CO2 and regenerate AS at the same time. In this study, process parameters of this route were investigated in detail, and the related extraction mechanism was discussed. It was found that 94.5% of calcium species in wollastonite was converted into CaSO4, 94.8% of which was subsequently carbonated. The extraction efficiency of the roasting stage did not exceed 39% due to its low mass transfer rate resulting from the high viscosity of liquid ammonium bisulfate and presence of silicon dioxide (SiO2) and CaSO4 species on the surface of unreacted wollastonite. Preliminary energy analysis showed that a net reduction of CO2 emission of about 347 kg could be achieved for the mineralization of 1000 kg of CO2.
       
  • Uranium and molybdenum recovery from copper leaching solutions using ion
           exchange
    • Abstract: Publication date: Available online 5 January 2019Source: HydrometallurgyAuthor(s): Pedro Orrego, José Hernández, Alonso Reyes This work shows the technical feasibility to recover uranium and molybdenum from industrial copper leaching solutions (PLS). Both were obtained as by-products from hydrometallurgical operations of the Chilean copper mining industry, using the ion exchange technique. This process recovered uranium and molybdenum, without disturbing or changing the normal operation of the overall copper production process. Uranium concentration was 17 mg/L, while molybdenum concentration was 50 mg/L. Four different anionic resins were tested, along with the influence of impurities over the breakthrough and saturation points achieved. In a first instance, two resins were chosen based on their Langmuir parameters, namely, maximum load capacity (Qmax) and separation factor (RL): L-MP62 and M43. The overall dynamic process consisted in a pre-conditioning step for the resin, using a weak hydrochloric acid solution. Next, the copper PLS solution feeds the fixed bed of the ion exchange column. Once the PLS solution saturates the anionic resin, a hydrochloric solution extracts uranium, and a sodium hydroxide solution extracts molybdenum. The final products were purified elution solutions with 500 mg/L uranium and 800 mg/L molybdenum, respectively.
       
  • Recovery of nickel and molybdate from ammoniacal leach liquors of spent
           HDS catalysts using chelating ion exchange resin
    • Abstract: Publication date: Available online 3 January 2019Source: HydrometallurgyAuthor(s): Bharat Padh, P.C. Rout, G.K. Mishra, K.R. Suresh, B. Ramachandra Reddy Spent hydrodesulphurization (HDS) catalysts containing valuable Mo and Ni ions are potential source for the recovery of Mo and Ni from the point of commercial, environmental and conservation of natural mineral resources. In the present study, oxidative roasting of spent HDS catalyst followed by ammonia leaching results in the leach liquor with about 15.3 g/L Mo (~85% recovery), ~125 g/L (NH4)2SO4 and ~0.9 g/L Ni as impurity. Therefore Ni separation from this ammoniacal molybdate leach liquor is essentially the first step to obtain high pure molybdate and ammonium sulfate solution. In this study, separation of nickel from ammoniacal molybdate leach liquor was reported using commercial chelating iminodiacetate resin, Lewatit TP207 by batch and column methods. Optimization of process parameters include equilibration time, acidity of leach liquor, aqueous flow rate, metal concentration, loading capacity of resin for Ni during sorption of Ni, desorption of nickel from loaded resin and stability and reuse of resin in continuous column experiments. Feed leach liquor of pH>8.0 is important to achieve clear separation of Ni from Mo. Loading capacity of resin and break through curves are optimized to achieve
       
  • Recovery of Pd(II) and Pt(IV) from leach liquors of automotive catalysts
           with calixarene-based di-n-alkylamino extractants in saturated hydrocarbon
           diluents
    • Abstract: Publication date: Available online 3 January 2019Source: HydrometallurgyAuthor(s): Manabu Yamada, Yu Kaneta, Muniyappan Rajiv Gandhi, Uma Maheswara Rao Kunda, Atsushi Shibayama The solubilities of eight p-di-n-alkylaminomethylcalix[4]arenes (alkyl: methyl to n-octyl = 1–8) in saturated hydrocarbon diluents commonly used as industrial diluents were investigated. Calixarene-based amino extractants with longer alkyl chains dissolved more readily in the saturated hydrocarbon diluents. Although 8 dissolved in kerosene, 1-decanol had to be added as a “phase modifier’” in order to inhibit the formation of a third phase on the Pd(II) and Pt(IV) extraction systems. The optimal mixing ratio of kerosene with 1-deconol was found to be 50:50 (v/v%). Pd(II) and Pt(IV) were effectively recovered from the leach liquors of automotive catalysts using 8 and this kerosene/1-decanol mixed diluent. Furthermore, the results of reusability tests performed using the regenerated organic phase consisting of 8 and the kerosene/1-decanol mixed diluent indicate that Pd(II) and Pt(IV) were extracted at relatively high efficiencies even after five extraction/stripping cycles.Graphical abstractUnlabelled Image
       
  • Can hydrogen sulphide gas be produced during alkaline leach of enargitic
           copper concentrates'
    • Abstract: Publication date: Available online 3 January 2019Source: HydrometallurgyAuthor(s): Gonzalo Montes-Atenas, Rodrigo Ladrón de Guevara, Katherine Lizama-Allende, F. Valenzuela The usual answer to the question stated in the title of this manuscript would be a definitive no due to the high stability of dissolved sulphide ions in water under strong alkaline conditions; nevertheless, experimental results presented in this research shows the opposite. Two arsenic-bearing copper concentrates coming from two different Chilean mine sites were used to carry out alkaline sulphide leach experiments. One of them (Concentrate 1) exhibits a P80 of 45 μm and 3.8% arsenic while the other (Concentrate 2) has a P80 of 98 μm and 2.3% arsenic. The arsenic extractions at 60 and 90 °C after 2 h reaction for concentrates 1 and 2 are around 10 and 80% and 14 and 93%, respectively.More relevantly, notwithstanding the strong alkaline conditions used in the experiments, the production of toxic hydrogen sulphide gas was detected and measured in tests performed at 90 °C. The molar ratio between the arsenic leached and the formation of hydrogen sulphide is 20:1 and 5:1 for concentrate 1 and 2, respectively. Stoichiometric computations associated to the mechanisms of carbonation of alkaline solutions and to the thermodynamic predominance of H2S at high pH values cannot fully explain the significant quantity of gas formed during the leaching process. One hypothesis to explain the formation of the gas is mineralogy related. It involves the occurrence of specific parallel secondary reactions taking place at the solid-liquid interface triggering the increase of the local acidity and producing the gas. Due to the high concentration of sulphide ions in solution and the high temperature conditions, the gas is not fully scrubbed by the strong alkaline solution. Looking at the mineralogy of the gangue material in both concentrates, the mass ratio of the gas produced between both concentrate matches the mass ratio of galena, haematite, goethite and kaolinite present in both concentrates suggesting that these minerals would be responsible for producing the gas. Reactions associated to each one of the mentioned species are presented suggesting two different mechanisms for local acidification. This finding would have a strong impact on the implementation of the process at large scale safety-wise.
       
  • Dephosphorization of unroasted oolitic ores through alkaline leaching at
           low temperature
    • Abstract: Publication date: Available online 31 December 2018Source: HydrometallurgyAuthor(s): Long Zhang, Richard Machiela, Prajesh Das, Mingming Zhang, Timothy Eisele Roasting followed by acid leaching has long been an established dephosphorization technique for processing the goethite iron ore in the past. However, given the high-energy requirement in the process, there still exists further room for improvement. The present study of phosphorus removal from an unroasted iron ore via alkaline leaching method examined the possibility of dephosphorization from goethite ore at low temperature. The iron ore concentrate used in this study is an oolitic type of iron ore consisting primarily of goethite, in which phosphorus does not form a discrete mineral phase, but instead is diffused throughout the entire volume of the ore. This study reveals that the reduction of particle size, the increase in both temperature and hydroxyl ion [OH¯] concentration all promote phosphorus removal. About 50% of the phosphorus can be removed in relatively low [OH¯] concentration (1.25 M), about 80% phosphorous removal was attained after further increasing the [OH¯] concentration to 15 M resulting in 0.1% phosphorus in final solids with no iron losses, which was comparable to roasting followed by acid-leaching route. The optimum conditions was identified as temperature of 85 °C, [OH¯] concentration of 15 M, 0.025–0.038 mm particle size, and 10 min of leaching time with S/L ratio of 0.25 g/ml, in which P level can be reduced from 0.73 to about 0.1 wt%P. Additionally, leaching solution was demonstrated to be readily regenerated using hydrated-lime with comparable leaching ability in terms of phosphorus removal compared to fresh solution. No significant mineralogical change observed other than the uniform removal of phosphorus during the process.
       
  • Leaching of synthetic Ca3WO6 with ammoniacal ammonium carbonate solution
           under atmospheric pressure: A fundamental study
    • Abstract: Publication date: Available online 31 December 2018Source: HydrometallurgyAuthor(s): Xiangming Xu, Kechao Zhou, Xiaobin Li, Qiusheng Zhou, Tiangui Qi, Guihua Liu, Zhihong Peng In (NH4)2CO3 solution, leaching Ca3WO6-bearing product converted from tungsten concentrate can directly obtain ammonium tungstate solution, and thus eliminates high-salinity wastewater discharge in ammonium paratungstate manufacture. Possible reactions of Ca3WO6 leaching in aqueous ammoniacal ammonium carbonate solution under atmospheric pressure were investigated thermodynamically and experimentally. The results show that tungsten in Ca3WO6 can be efficiently leached out by forming CaCO3(s) and (NH4)2WO4 (aq) in aqueous ammoniacal ammonium carbonate solution, while raising ratio of total ammonia to total carbon in solution and forming calcite are beneficial to increase the WO3 leaching ratio. Whereas the secondary reactions of Ca3WO6 with H2O and/or Ca (OH)2/CaCO3 with (NH4)2WO4 may occur and thus CaWO4 forms in the leaching, decreasing WO3 leaching ratio especially in concentrated (NH4)2WO4 solution and in case of forming vaterite. In addition, a three-layer cover was observed on the unreacted Ca3WO6 and hinders the leaching process. Through simultaneous grinding and leaching, both high WO3 leaching ratio and high WO3 concentration leachate can be achieved by increasing ratio of total ammonia to total carbon in NH3-(NH4)2WO4- (NH4)2CO3-H2O system. These results are helpful to optimize the leaching process of the converted product with Ca3WO6 by roasting tungsten-containing materials.
       
  • Leaching and recovery of phosphate and rare earth elements from an
           iron-rich fluorapatite concentrate: Part II: Selective leaching of calcium
           and phosphate and acid baking of the residue
    • Abstract: Publication date: Available online 30 December 2018Source: HydrometallurgyAuthor(s): Faraz Soltani, Mahmoud Abdollahy, Jochen Petersen, Rahul Ram, S.M. Javad Koleini, Davood Moradkhani Apatite concentrate is an important source of phosphate and contains significant amounts of rare earth elements (REEs). In this study, the possibility of selective phosphoric acid leaching of phosphate and calcium from the Esfordi (Yazd province, Iran) apatite concentrate, containing 16.3% phosphorus, 37.1% calcium, 2.9% iron and 1.2% REEs was investigated. REEs concentrated in the leaching residue were processed using acid baking and bicarbonate precipitation methods. In the phosphoric acid leaching process, almost all the Ca and phosphate of the concentrate were leached from the concentrate, whereas only about 1% of the REEs were leached. By leaching the concentrate with 25% phosphoric acid at 90 °C and 1200 rpm, a residue containing 17.5% REEs, 4.8% phosphorus and 28.5% iron was obtained. The residue was acid baked, water leached and processed for removal of iron and recovery of REEs. Acid baking at 270 °C with acid to solid ratio of 2 (w/w) for 5 h led to 95% leaching of REEs. By increasing the pH of the leachate to 3.9, all the iron and phosphate were precipitated within 2 h. Finally, REEs were precipitated from the iron-free solution by using the bicarbonate precipitation method, and a product containing 39% of total REEs was produced. The results demonstrate that the three-stage process is an elegant method for processing of the Esfordi concentrate to produce phosphoric acid and an iron-free REE carbonate concentrate.Graphical abstractUnlabelled Image
       
  • The effect of ore mineralogy on the electrochemical gold dissolution
           behavior in various cyanide and oxygen concentrations: Part I. Effect of
           sulfidic ores containing heavy metals
    • Abstract: Publication date: Available online 30 December 2018Source: HydrometallurgyAuthor(s): Rina Kim, Ahmad Ghahreman The effect of heavy metals-containing gold ore mineralogy on gold oxidation kinetics in solutions with various free cyanide (CN) and dissolved oxygen (DO) concentrations was studied by electrochemical tests. To effectively simulate the cyanide gold leaching conditions, the electrochemical experiments were carried out in the slurries of the ores. The results of the linear sweep voltammetry tests showed three significant gold oxidation peaks. The peak potentials and the corresponding current densities were dependent on the composition of the ores in the test slurries, and the CN and DO concentrations of the test solutions. The heavy metal concentration of the ores also effectively changed the electrochemical response of the tests.The highest gold oxidation kinetics were observed in a pyritic sample with 1800 ppm Pb, 640 ppm Ag and 195 ppm Hg (sample 1). The fastest gold oxidation kinetics were registered at −0.2 V vs. Ag/AgCl when DO was 8.3 mg/L, and the corresponding Au oxidation peak current densities were 4.75 and 7.07 mA/cm2 at 600 and 900 mg/L free CN, respectively. The Au oxidation was assisted by cementation reaction between the aqueous Hg and/or Ag species, and metallic gold. The weak lead deposition was also observed. However, the positive effect of Hg on the gold oxidation kinetics was depressed at higher DO (37.0 mg/L) concentrations. Unlike Hg, the effect of Ag on increasing the gold oxidation kinetics was shown to be independent of the solution DO.The second sample of the study, sample 2, was a sulfidic gold ore with 0.25% galena (PbS). The results showed that the presence of galena in an electrochemical gold oxidation test could increase the gold oxidation kinetics. In tests with 8.3 mg/L DO, the current densities of 2.80 and 5.23 mA/cm2 at 600 and 900 mg/L CN solutions, respectively, were obtained at −0.4 V vs. Ag/AgCl. Increasing DO to 37.0 mg/L did not improve the gold oxidation kinetics.Based on the results of this study, the presence of the specified heavy metals is most effective in gold oxidation kinetics if the free CN concentration is high and the DO concentration is low. Besides, the electrochemical methodology introduced in this study could offer a solution for determining the leaching parameters.
       
  • Recovery of lithium in seawater using a titanium intercalated lithium
           manganese oxide composite
    • Abstract: Publication date: Available online 26 December 2018Source: HydrometallurgyAuthor(s): Taegong Ryu, Junho Shin, Seyed Majid Ghoreishian, Kang-Sup Chung, Yun Suk Huh In this study, recovery of lithium in seawater using a titanium-intercalated lithium manganese oxide composite (LTMO) was investigated along with its adsorption capacity and durability. To minimize manganese dissolution during the extraction of Li+ by acidic treatment, a spinel type of LTMO was synthesized by the high-energy milling of a titania (TiO2), lithium carbonate (Li2CO3), and manganese carbonate (MnCO3) mixture and subsequent heat treatment. X-ray diffraction and thermogravimetric analyzer confirmed that Ti was well intercalated into the spinel structure of lithium manganese oxide (LMO). The effects of calcination temperature and Ti content on LTMO structure, lithium uptake, and adsorbent stability were investigated. Kinetic analysis showed that adsorption by LTMO followed pseudo-second-order kinetics, with a correlation coefficient in excess of 0.99. Adsorption by LTMO fitted the Langmuir isotherm well, with a correlation coefficient higher than 0.99, and LTMO exhibited higher theoretical maximum adsorption capacity than LMO (up to 21.9 mg g−1 vs. 19.6 mg g−1). In addition, LTMO showed high selectivity for lithium ions in the presence of competitive cations.
       
  • Oxidative precipitation of cerium in acidic chloride solutions: part I –
           Fundamentals and thermodynamics
    • Abstract: Publication date: Available online 21 December 2018Source: HydrometallurgyAuthor(s): James McNeice, Rina Kim, Ahmad Ghahreman Cerium, the most abundant rare earth element (REE), is typically the largest component of the hard rock REE ores. Demand for less prevalent REE, such as neodymium and dysprosium, have led to a market saturation and price collapse of cerium. One method of improving the economics of REE processing operations is to effectively remove cerium from the solution prior to SX. This is accomplished by the oxidation of Ce (III) to Ce (IV), which precipitates as cerium hydroxides. This study probes the efficacy of four oxidants for oxidative cerium precipitation from chloride solutions: hydrogen peroxide, sodium hypochlorite, potassium permanganate, and Caro's Acid. Cerium oxidation was tested using these oxidants at varying stoichiometry, a pH range of 1.0 to 4.0, temperatures of 25, 45, and 65 °C, and varying cerium concentrations. Kinetic constants were calculated from time sampled data. Complete cerium removal is achievable using potassium permanganate and Caro's acid in the absence of other REE. Thermodynamic data was used to create theoretical speciation and pourbaix plots illustrating the conditions in which cerium was oxidized using these reagents.
       
  • Continuous solvent extraction operations for the separation of W and Mo in
           high concentrations from ammonium solutions with acidified N1923
    • Abstract: Publication date: Available online 21 December 2018Source: HydrometallurgyAuthor(s): Zhihua Li, Guiqing Zhang, Li Zeng, Wenjuan Guan, Liansheng Xiao, Qinggang Li, Zuoying Cao, Xiuyuan Lu To separate tungsten and molybdenum from the ammonium solution containing 31.2 g/L WO3 and 32.5 g/L Mo, the continuous operations of solvent extraction were carried out using acidified primary amine extractant of N1923 in mixer-settlers. Thermodynamic analysis of the WMoH2O system showed that W(VI) could be selectively extracted over Mo (VI) by primary amine since WO42− was preferentially transformed to polymeric ions as the pH decrease. The results of 58 h continuous operations indicated that the solvent extraction process could be used effectively to separate W(VI) from ammonium molybdate solutions. The raffinate contained only 6.0–7.0 mg/L WO3 with a mass ratio of WO3/Mo less than 3.45–4.99×10−4, which can be used to produce ammonium molybdate with MSA-0 grade of Chinese National Standards. Compared with traditional methods on separation of W and Mo, the new process exhibited obvious advantages of low cost, high separation factor of W/Mo, environmental friendliness, which is expected to make good economic and social benefits.
       
  • An integrated approach to evaluating the effect of associated minerals on
           copper ammoniacal thiosulfate leaching of a gold–bearing sulfide
           concentrate
    • Abstract: Publication date: Available online 21 December 2018Source: HydrometallurgyAuthor(s): José A. Tamayo, Angel M. Meléndez, Jorge A. Calderón This work proposes a method for the evaluation of the effect of galvanic interactions between intergrown sulfide-mineral grains present in a thiosulfate leaching system, based on a combination of electrochemical measurements. Several common associated minerals in complex sulfide ore (CSO), as well as high purity sulfide minerals (pyrite, arsenopyrite, chalcopyrite, sphalerite, and galena), were used to develop and test the method. The reactivity of the CSO and each individual sulfide mineral in an ammoniacal thiosulfate solution was determined by voltammetry and chronoamperometry, using carbon paste electrodes and rotating disk electrodes (RDE). Secondary phase formation and the surface alteration of both the individual and associated minerals were evaluated by in-situ Raman spectroscopy and ex-situ cyclic voltammetry in 0.1 M NaNO3 aqueous solution. Chalcocite (Cu2S) and covellite (CuS) were identified as intermediate products of chalcopyrite leaching, while pyrite was oxidized to ferrous hydroxide and later to magnetite. Results showed that pyrite in CSO acts as a cathodic side, promoting the reduction of oxygen. Thus, the oxidation of pyrite was delayed due to the galvanic protection offered by arsenopyrite and chalcopyrite. Mineralogy and evaluation of the mineral textures both of the ore and its modification as a result of leaching were used to validate the method.Graphical abstractUnlabelled Image
       
  • The electrochemistry and kinetics of the oxidative dissolution of
           chalcopyrite in ammoniacal solutions. Part II – Cathodic reactions
    • Abstract: Publication date: Available online 21 December 2018Source: HydrometallurgyAuthor(s): T. Moyo, J. Petersen, M.J. Nicol The cathodic reduction of copper(II) and oxygen on the surface of chalcopyrite have been studied in ammonia-ammonium sulphate using cyclic voltammetry and chrono-amperometry. The predominant cathodic reaction in the oxidative dissolution of chalcopyrite in ammoniacal solutions has been established to be that of the reduction of copper (II). The rate of the cathodic reaction is inversely dependent on the total ammonia concentration and although the tetra-ammine copper(II) ion is the most dominant species under these conditions, it is suggested that the tri-ammine complex is the most electroactive under these conditions. It was shown that both the reduction of copper(II) and oxidation of copper(I) occur simultaneously at potentials close to the mixed potentials of chalcopyrite under the conditions of this study and apparent mass transfer limitations observed on the reaction were concluded to be due the outward migration of the product of Cu(I) ions from the mineral surface.
       
  • Desilication of concentrated alkali solution by novel desilication reagent
           calcium hydroferrocarbonate: Part II. Desilication reaction and kinetics
    • Abstract: Publication date: Available online 18 December 2018Source: HydrometallurgyAuthor(s): Tao Hong, Jun Luo, Manbo Liu, Shili Zheng, Yi Zhang Using a hydroferite desilication reagent, calcium hydroferrocarbonate (CHFC), the desilication reaction in concentrated caustic aluminate solution was studied. The results indicated that process parameters, such as temperature, Na2O concentration, molar ratio of Na2O to Al2O3, and initial mass ratio of alumina to silica (mass ratio of alumina to silica), significantly affected the reaction efficiency. The reaction kinetics were found to exhibit a reaction order of 1.3 ± 0.15 for desilication; the empirical rate constant k was 64.4 ± 2.4 and the apparent activation energy Ea was 25.8 ± 3.2 kJ/Mol, which was much lower than the values obtained by adding Ca(OH)2, C3AH6(calcium Hydroaluminate, 3CaO·A12O3·CaCl2·6H2O), and Friedel's salt (3CaO·A12O3·CaCl2·10H2O). In the desilication process, silica reacts with CHFC on the surface to form hydroandradite and calcium aluminum iron hydroxide. Subsequently, with an increase in Na2O concentration and temperature, hydroandradite and calcium aluminum iron hydroxide dehydrated to form calcium aluminum iron silicate and Fe(OH)3
       
  • Purification of high iron wet-process phosphoric acid via oxalate
           precipitation method
    • Abstract: Publication date: Available online 17 December 2018Source: HydrometallurgyAuthor(s): H.M. Abdel-Ghafar, E.A. Abdel-Aal, M.A.M. Ibrahim, H. El-Shall, A.K. Ismail A method has been developed to reduce the iron content in phosphoric acid produced by the dihydrate wet process from open cast phosphate rock of Abu-Tartur mine in Egypt. In this method, oxalic acid was used to precipitate iron as ferrous oxalate dihydrate (FeC2O4.2H2O). The achieved removal efficiency of iron was about 91% due to the low solubility of the precipitated salt in dilute phosphoric acid medium. The maximum P2O5 losses were less than 1.0%. The optimum conditions of oxalate precipitation method were obtained using synthetic dilute phosphoric acid (28% P2O5, 390 g/L H3PO4) with iron content amounting 2.8% (w/w) Fe2O3 (26.3 g/L Fe). It was found that, the clarification time, reaction temperature, P2O5 concentration and oxalic acid dose were 2 h, 60 °C, 28% P2O5 and 7.5 g oxalic acid/100 g 28% P2O5 acid, respectively. These conditions were applied using wet-process phosphoric acid (26% P2O5). Firstly, ferric ions in the acid were reduced to ferrous ions using iron scrap, followed by oxalic acid addition. Mostly all iron ions in the solution are in the divalent state at Electro Motive Force (EMF) values less than 275 mV. The solubility of ferrous oxalate dihydrate was measured at different temperatures and phosphoric acid concentrations. A recovery study for oxalic acid from the precipitated FeC2O4.2H2O has performed.
       
  • Effect of microwave heating on the pressure leaching of vanadium from
           converter slag
    • Abstract: Publication date: Available online 8 December 2018Source: HydrometallurgyAuthor(s): Lei Tian, Zhifeng Xu, Lijie Chen, Yan Liu, Ting-an Zhang In this paper, a comparison is made between the leaching associated with microwave heating (MHL) and electric heating (EHL) of converter vanadium slag in an autoclave under an oxygen pressure of 0.4 MPa. The comparative study of the leaching processes showed that the vanadium leaching efficiency reached 46% in 20 min using EHL, whereas it reached 96% under the same condition when MHL was used. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses of MHL residue showed that decomposition of the spinel phase in the converter vanadium slag can be accelerated through this process. In addition, MHL can reduce the granularity and make the surface of the particles more porous. In general, using MHL is more effective than EHL, for the leaching of converter vanadium slag in pressure leaching process. Through kinetic studies of MHL and EHL, the activation energies of vanadium leaching were determined to be 14.8 and 40.5 kJ/mol, respectively. The reaction rate depends on acid concentration as well as oxygen partial pressure. The order of reaction with respect to H2SO4 concentration was found to be 0.99 for MHL and 2.21 for EHL. The order of reaction with respect to the oxygen partial pressure was found to be 0.51 and 0.65 for MHL and EHL, respectively. The kinetic equations are derived and reported for MHL and EHL processes.
       
  • Cr(III) and Fe(II) recovery from the polymetallic leach solution of
           electroplating sludge by Cr(III)-Fe(III) coprecipitation on maghemite
    • Abstract: Publication date: Available online 29 November 2018Source: HydrometallurgyAuthor(s): Tong Yue, Zhen Niu, Yuehua Hu, Haisheng Han, Deliang Lyu, Wei Sun The separation of Cr(III) from the polymetallic leaching solution is a typical problem encountered during the recycling of electroplating sludge. In this paper, a novel method was proposed to recover Cr(III) and Fe(II) synchronously by forming the Cr(III)-Fe(III) coprecipitates on the surface of maghemite (γ-Fe2O3) fine particles with Fe2(SO4)3 solution as the supplemental Fe source. The results showed that high Fe(III) to Cr(III) ratio in solution promoted the hydrolysis and precipitation of Cr(III). In addition, the maghemite particles, served as the crystal nuclei, could induce the formation of the core-shell structured Cr(III)-Fe(III) coprecipitates on its surface and accelerate the sedimentation of the coprecipitates in the magnetic field. By using a two-stage Cr(III)-Fe(III) coprecipitation process, the recoveries of Cr and Fe reached 96.17% and 99.39%, and the grades of Ni, Cu, and Zn in the coprecipitates were at 0.41%, 0.38%, and 0.22%, respectively. The obtained coprecipitates can be recycled as the feed material of chromium smelting after heat treatment. This method is simple and efficient for high-concentration Cr3+ solution treatment, which is beneficial for the sustainable development of resources and environment.Graphical abstractUnlabelled Image
       
  • The adsorption of gold(I) on minerals and activated carbon (preg-robbing)
           in non-ammoniacal thiosulfate solutions - effect of calcium thiosulfate,
           silver(I), copper(I) and polythionate ions
    • Abstract: Publication date: Available online 24 October 2018Source: HydrometallurgyAuthor(s): O. Sitando, G. Senanayake, X. Dai, P. Breuer The ability of some typical gangue minerals and activated carbon to adsorb gold(I) (preg-robbing) in non-ammoniacal thiosulfate solutions was examined at different calcium thiosulfate concentrations. In the absence of calcium thiosulfate, sulfide minerals such as pyrite and chalcopyrite, and carbon were highly preg-robbing with 100% gold being adsorbed within half an hour. The oxide minerals examined including kaolinite, goethite and hematite were significantly less preg-robbing under the same conditions. The presence of free thiosulfate can significantly reduce or eliminate the preg-robbing of gold on mineral surfaces. With an initial thiosulfate concentration of 0.1 M, gold adsorption by oxide minerals was completely eliminated, while that of sulfide minerals and carbon was insignificant at 0.2 M free thiosulfate.Copper(I) was found to enhance the preg-robbing of gold by oxide minerals but to reduce the preg-robbing of gold by sulfide minerals and by carbon. Similar effect of silver(I) was observed except for chalcopyrite. Trithionate, a by-product of thiosulfate degradation, has no significant effect on the preg-robbing of gold(I). Tetrathionate, another by-product of thiosulfate degradation, significantly increases the preg-robbing of gold(I) onto pyrite. Activated carbon enhances the degradation of tetrathionate to trithionate and thiosulfate, the latter helps stabilise the gold(I) in solution.
       
  • Dissolution of calcium, phosphate, fluoride and rare earth elements (REEs)
           from a disc of natural fluorapatite mineral (FAP) in perchloric,
           hydrochloric, nitric, sulphuric and phosphoric acid solutions: A kinetic
           model and comparative batch leaching of major and minor elements from FAP
           and RE-FAP concentrate
    • Abstract: Publication date: Available online 6 September 2018Source: HydrometallurgyAuthor(s): A.M.T.S. Bandara, G. Senanayake Some rare earth phosphate minerals are associated with fluorapatite (FAP) in phosphate ores which make them a potential source of rare earth elements (REEs), to satisfy the increasing demand of REEs, especially for green energy technology and new energy materials. Previous studies have shown that the leachability of different elements which may be categorised as REEs and non-REEs in different acid solutions with the possibility of selective leaching of non-REEs by phosphoric acid to produce a REE rich leach residue which can be processed separately. This study investigates the dissolution of calcium, phosphate, fluoride and REEs from a rotating disc of a natural FAP mineral sample in perchloric, hydrochloric, nitric, sulphuric and phosphoric acid solutions under various leach conditions including different acid concentrations and temperatures and compares the results with batch leaching of natural FAP mineral and RE-FAP concentrate particles.The dissolution rate of REEs, which occur as minor elements in FAP mineral disc, are lower than that of the major elements: Ca, P and F. Higher dissolution rate of calcium from FAP disc in solutions of HCl, HNO3 and H2SO4 compared to HClO4 at high acid concentrations are due to the influence of Cl−, NO3− and SO42− ions, caused by association with Ca2+ ions in disc leaching, but precipitation of CaSO4 retard particle leaching in H2SO4. Despite the lower leaching rates of REEs due to low abundance of REEs on FAP mineral disc surface, the rates in 0.5 mol L−1 acid solutions follow the order H2SO4, HNO3 > HCl > HClO4 > H3PO4 indicating the beneficial effect of ion-association of the type RE(III)-sulfate/nitrate compared to RE(III)-phosphate precipitation. The higher leaching efficiencies of REEs in H3PO4 during first 10 min also decreases with prolonged leaching due to RE(III)-phosphate precipitation. The leaching efficiencies of Ca, Sr, Fe, Al and Mg are in the range 50–100% in 3.25 mol L−1 HCl, HNO3, HClO4 and H3PO4, compared to REEs, Th and U which vary in the range 20–80%, depending upon the formation of complex species or precipitation. A comparison between elemental composition of natural FAP mineral and a RE-FAP concentrate and their similarities in leaching behaviour in different acids is also presented highlighting the exceptional behaviour of phosphoric acid to selectively leach majority of non-REEs leaving REEs and silica in the leach residue.The surface reaction kinetic models and mechanisms are used to show that the dissolution reaction of calcium is mainly controlled by a chemical phenomenon in strong acids and phosphoric acid at the temperature range 25–50 °C. The experimental reaction orders with respect to H+ concentration in HCl, HNO3, HClO4, H2SO4 and H3PO4 in the range 0.46–0.93 for the dissolution reaction of calcium and/or phosphate are explained on the basis of stoichiometric dissolution and the influence of ion-association of anions with H+ and Ca2+.
       
 
 
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