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ENGINEERING (1307 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
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at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
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Journal Cover
Applied Clay Science
Journal Prestige (SJR): 0.992
Citation Impact (citeScore): 4
Number of Followers: 6  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0169-1317
Published by Elsevier Homepage  [3155 journals]
  • Exchange reactions of zinc hydroxide-sulfate minerals in halide solutions
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Tsveta Stanimirova The possibilities of exchange reactions in two types of layer Zn-hydroxy sulfate minerals with neutral and negatively charged hydroxide layer – namuwite (Zn4(OH)6(SO4)·4H2O) and gordaite (NaZn4(OH)6(SO4)Cl·6H2O) – were studied. As starting materials, synthetic analogs of these minerals are used. Through direct synthesis, besides the known namuwite, gordaite, and its Ca2+ form, a series of new cationic (K+, NH4+) and anionic (Cl− and Br−) gordaite forms were synthesized. The K+, NH4+ content is respectively about 1/3 and 2/3 of the nominal compositions. The determined characteristics of Br-forms showed similarity with corresponding chloride forms.The results of the experimental study of the interaction between gordaites and namuwite and various halide solutions showed the realization of three types of solid-state exchange reactions: cation exchange, simultaneous cation-anion exchange, and water molecule-halide anion exchange. All samples were characterized by powder XRD and EDS chemical analysis, and the transformation mechanism was monitored by SEM investigation.By cation exchange, the all cationic gordaite forms were formed, and in addition, Sr2+-form was also obtained. Mutual conversions between the isovalent cations Na+-K+, Ca2+-Sr2+, and between all possible combinations of heterovalent cation pairs were established.Regardless of the charge of the hydroxide layer – neutral (namuwite) or negatively charged (gordaites), due to the stronger interaction of halide anion with the interlayer cations than that with the hydroxide layer's tetrahedral Zn2+ cation, the anion exit together with the leaving cations was observed, causing the simultaneous cation-anion exchange or mutual substitution of H2O molecules and halide anions. In the first case, the gordaite Br-forms from chloride one are formed. However, under treatment of the all various gordaite forms with iodide solutions, no exchange was observed. The big size of I− anion probably prevents its occupation of the apical position of hydroxide layer's Zn-tetrahedron and provokes the formation of new pure zinc-hydroxy-sulfate-hydrate phase with unknown specific structure.In the second case, the solid-state mutual substitution of H2O molecules and halide anions halide in the apex of the Zn-tetrahedron resulted in the formation of different zinc hydroxy sulfate hydrates, depending on the treating water amount. The reversible reaction caused a formation of different cationic gordaite forms under treatment of namuwite with chloride solutions of Na+, K+, NH4+, Ca2+, and Sr2+.The treatment of gordaites and namuwite with chloride solutions of some of the other alkaline and alkaline earth metals Li+, Mg2+, and Ba2+ resulted in gordaite dissolution and subsequent pseudomorphic simonkolleite crystallization. The simonkolleite formation is probably due to geometric difficulties for Li+ and Mg2+ interlayer incorporation caused by their great hydration capability and for Ba2+ due to its ability to form insoluble barite.
       
  • Folic acid-layered double hydroxides hybrids in skin formulations:
           Technological, photochemical and in vitro cytotoxicity on human
           keratinocytes and fibroblasts
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Cinzia Pagano, Luana Perioli, Loredana Latterini, Morena Nocchetti, Maria Rachele Ceccarini, Marco Marani, Daniele Ramella, Maurizio Ricci Folic acid (FA) is a key factor in the physiological processes of cell metabolism; as it is involved in DNA synthesis and repair, it can be used in the treatment of aged and photo-damaged skin. The main drawbacks associated to FA use, particularly for topical applications, are the limited solubility and the sensitivity to UV rays.Hybrids of FA with two kinds of layered double hydroxides (ZnAl-LDH and MgAl-LDH) were prepared and characterized showing suitable particle size, flow properties and UV photoprotection. The introduction of FA-LDHs in the external water phase of O/W emulgels produced an enhancement of their flow properties; moreover, the spectrophotometric analyses showed that very good photostability is maintained even after their introduction into the formulations. In-vitro release studies showed that the FA-LDH containing emulgels promoted a sustained FA release as expected. Finally, the safety of FA-LDH was evaluated by in-vitro studies performed on human keratinocytes (HaCaT) and human primary dermal fibroblasts (as a skin representative). The obtained results showed a high cytotoxic effect of ZnAl-LDH-FA in both cell lines.Graphical abstractUnlabelled Image
       
  • Organic functionalization of clay aerogel and its composites through
           in-situ crosslinking
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Omar Abo Madyan, Mizi Fan Clay aerogel composites have great potential for a wide range of applications; however, their high moisture absorbance and inferior mechanical properties have to be addressed. This paper presents crosslinking techniques to develop clay/PVA aerogel composites through an environmentally freeze-drying process using water as a solvent. Water soluble isocyanate and organosilane compounds, namely aliphatic polyisocyanate (Wcro1™) and 3-glycidoxypropyltrimethoxysilane (Wcro2™) were employed and their crosslinking mechanisms were studied. The results of the aerogels characterizations showed that the chosen crosslinkers were able to generate substantial crosslinking reactions. The crosslinked clay/PVA aerogel gave rise to significant improvements in their mechanical and physical properties. The moisture absorbance of the composites was reduced by 27%, while retaining dimensional stability. The developed functionalized clay/PVA aerogels also increased the liquid absorption capacity by 3 times, the compressive modulus increased by 6 folds from 0.48 to 3.6 MPa and the thermal conductivity reduced from the 0.043 to 0.039 W/mK.Graphical abstractUnlabelled Image
       
  • Equilibrium and kinetic studies of caffeine adsorption from aqueous
           solutions on thermally modified Verde-lodo bentonite
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Maria Fernanda Oliveira, Meuris G.C. da Silva, Melissa G.A. Vieira The removal of pharmaceutical compounds from water and wastewater is a subject of interest to the scientific community, since these substances have been related to several environmental and health problems. Usual techniques are not effective to remove pharmaceuticals and adsorption is an alternative technology with high potential to treat contaminated water. This work aimed to investigate the use of thermally modified bentonite Verde-lodo for batch adsorption of caffeine from aqueous solution. A kinetic study occurred at atmospheric pressure and 25 °C. The adsorption equilibrium time was 40 h, and the models adjusted to experimental data were pseudo-first order, pseudo-second order, Boyd and intraparticle diffusion and the pseudo-second order model showed the best fit. The resistance to external film was the limiting step on mass transfer. The equilibrium study was performed at temperatures of 15, 25, 40 and 60 °C. The Langmuir model was adjusted to data and the highest adsorption capacity was obtained at 60 °C (0.73 mmol/g). The Freundlich and Dubinin-Radushkevich models were also fitted to the experimental curves. The first one showed the best fit for temperatures of 40 and 60 °C and the second was the best for temperatures of 15 and 25 °C. The characterization techniques of scanning electron microscopy, mercury porosimetry, helium pycnometry and nitrogen physisorption indicated changes on bentonite's surface, such as increase on the bulk density, reduction on skeletal density and reduction in the volume of micropores and mesopores.Graphical abstractUnlabelled Image
       
  • Retention of Pb and Cr(VI) onto slurry trench vertical cutoff wall
           backfill containing phosphate dispersant amended Ca-bentonite
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Yu-Ling Yang, Krishna R. Reddy, Yan-Jun Du, Ri-Dong Fan This study investigated the potential use of sodium hexametaposphate (SHMP) as an amendment in calcium bentonite (Ca-bentonite) and sand/Ca-bentonite backfill to enhance retention of two heavy metals, lead (Pb) and hexavalent chromium (Cr(VI)), commonly encountered in contaminated groundwater by conducting batch equilibrium experiments. The pH of the equilibrated bentonites and backfills was also measured. The results showed that the SHMP amendment and the presence of source chemicals lowered the equilibrium pH of the bentonites and backfills. All the tested bentonites and backfills exhibited nonlinear retention behavior of Pb and Cr(VI) which was well described by Langmuir and Freundlich models. SHMP amendment increased the Pb retention capacity of the bentonite and backfill by a factor of 1.45 and 1.72 respectively, whilst it helped little on improving Cr(VI) retention capacity of the bentonite and backfill. Moreover, the percent retention (PR) and partition coefficient (Kp) were found to increase first and then decrease with the initial metal concentrations, and the peak PS or Kp occurred at initial concentration of 874 mg/L for Pb retention on all tested bentonites and backfills, whilst 1 and 48 mg/L for Cr(VI) retention on the tested bentonites and backfills respectively. Based on the variations of PR and Kp with initial metal concentration, the enhanced retention of Pb on bentonite and backfill with SHMP amendment was pronounced when the initial Pb concentration was higher than the threshold value of 1642 mg/L. However, the bentonite, even though amended with SHMP, is not an ideal barrier material for Cr(VI) retention.
       
  • Assessing and modifying China bentonites for aflatoxin adsorption
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Fangqun Gan, Xiaoshuai Hang, Qiaoyun Huang, Youjun Deng Bentonites have been used to reduce or to diminish the toxicity of aflatoxins to animals and humans. Due to bentonites' large variations in mineral composition, and the dominant mineral smectite can differ in interlayer cation composition, charge density, charge origin, bentonites demonstrated more than ten fold of differences in aflatoxin adsorption capacity. To maximize the efficiency of local bentonites for aflatoxin detoxification, modifications of bentonites are often needed. The objectives of this study are to asses and to modify selected bentonites from China for aflatoxin detoxification. Thirteen Chinese bentonites were collected and evaluated for montmorillonite contents. A 6-fold difference in aflatoxin B1 (AfB1) adsorption capacity among these 13 natural bentonites were observed. Six bentonites, representing the low-, medium-, and high- adsorption for AfB1, were selected for detailed assessment and modification. The clay fractions of the bentonites (Na-saturated) were harvested and exposed to the following three treatments: (1) Ca saturation (Ca_), (2) Mg saturation and heating (Mg_Heat), (3) Mg saturation and heating then Ca saturation (Mg_Heat_Ca), respectively. These three treatments enhanced the AfB1 adsorption capacity of the six bentonites and the relative efficiency of the treatments follows the order of Mg_Heat_Ca>Mg_Heat>Ca_ in most of the six bentonites. Calcium saturation or heating can improve the clays' adsorption affinity and capacity for AfB1 mainly because of the reduction of cation exchange capacity (CEC). This assumption was confirmed by the change of CEC and single-point AfB1 adsorption capacity of bulk bentonites before and after heating. Our adsorption data suggest that some Chinese bentonites are generally suitable for AfB1 adsorption, and high selectivity can be achieved by optimizing their charge density. Similar approach should be applicable to other local bentonites worldwide.
       
  • Ethylene glycol monoethyl ether (EGME) adsorption by organic matter
           (OM)-clay complexes: Dependence on the OM Type
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Hongling Bu, Dong Liu, Peng Yuan, Xiang Zhou, Hongmei Liu, Peixin Du The ethylene glycol monoethyl ether (EGME) adsorption method has been used as an available technique for measuring the total specific surface area (TSSA) of soils and clay-rich rocks. However, the existence of organic matters (OM) has recently been proposed to affect the accurate measurement of the TSSA. To explore the effects of OM on the TSSA evaluation of clay-rich samples, EGME adsorption experiments were performed on OM and the OM-clay minerals (OM-clay) complexes that widely exist in soil and clay-rich rocks. Two types of OM, 12-aminolauric acid (ALA) and lauric acid (LA) were used, and montmorillonite (Mt) was selected as the representative clay mineral. OM-clay complexes with OM in interlayer space or OM-clay mixture with OM on the external surface of an expanding clay mineral were prepared to investigate the influence of occurrence sites of OM on the EGME adsorption. The combined methods of X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) were used to study the structural characteristics of the OM-clay complexes before and after EGME adsorption for revealing the EGME adsorption mechanisms. The results showed both the occurrence sites and the functional groups of OM significantly influence the EGME adsorption behaviour and TSSA for OM-clay complexes. As ALA intercalated into interlayer space of Mt, it can occupy parts of adsorption sites of EGME leading to a lower TSSA than that of Mt. While as LA located on the external surface of Mt, it affects access to the interlayer surface by the EGME and occupies parts of EGME adsorption sites of the external surface of Mt, resulting in lower adsorption capability and the slight smaller TSSA than Mt. In addition, EGME reacted strongly with LA producing excess TSSA, which brings about a great difference between LA-Mt and ALA-Mt on EGME adsorption behaviour. These fundamental results demonstrated that OM could strongly affect the EGME adsorption on the OM-Mt complexes and further influence detection of TSSA. The occurrence sites and the functional groups of OM in OM-clay complex must be considered when the EGME adsorption method is used for TSSA evaluation of such clay-rich rocks and soil samples.
       
  • On the potential of microbeam analyses in study of the ceramics, slip and
           paint of Late Bronze Age White Slip II ware: An example from the Canaanite
           site Tel Esur
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Golan Shalvi, Shlomo Shoval, Shay Bar, Ayelet Gilboa Microbeam Analyses using EPMA, pXRF, LA-ICP-MS and FT-IR were conducted in this study of Late Bronze Age (LBA) White Slip II ware (WS-ware) imports at the Canaanite site Tel Esur (Tel Esur WS). The WS-ware is typically decorated with black-brown geometric patterns painted over a white slip layer. The study of the WS-ware provides useful information and a multi-analytical database regarding the composition, ceramic technology, raw materials, origin and cultural issues. The results demonstrate that the LBA potters select raw materials suitable for production of ceramics, slip and paint. The ceramic-body of the WS-ware was made of raw material that has been an appropriate selection to produce a hard and thin-walled vessel. For accentuating the black decoration over the dark reddish-grey ceramic-body, the latter was covered with white slip layer. The black decoration was made of ferromanganese-based pigment, which allows black decoration through firing of the vessels at an oxidizing atmosphere. The raw materials for the production of the ceramics, slip and paint were selected from Cypriot red basaltic clay of weathered basalt province, white hydrothermal clay of altered basalt zone and umber ore, respectively. The Tel Esur White Slip II ware is proved analytically to be imported from Cyprus.
       
  • Enhancing hydrophilicity and permeation flux of chitosan/kaolin composite
           membranes by using polyethylene glycol as porogen
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Sonia Bouzid Rekik, Sana Gassara, Jamel Bouaziz, André Deratani, Semia Baklouti A novel chitosan/kaolin composite membrane with high flux and enhanced hydrophilicity was prepared by solvent casting and evaporation process in the presence of polyethylene glycol (PEG). The characterization of the as-fabricated membranes indicated that the combined effect of kaolin as reinforcing agent and PEG as porogen into a chitosan matrix showed significant influence on the morphology and hydrophilicity. Highly porous membranes with finger-like structure were obtained. Both size and density of the pores increased with increasing the PEG content from 0 to 3 wt%. The incorporation of the hydrophilic polymeric additive constructed a water channel network and increased the free volume within the composite matrix, contributing to the enhanced filtration performance of the resulting membrane. Additionally, their mechanical, thermal and chemical stability showed a large improvement compared to the unmodified one.Graphical abstractUnlabelled Image
       
  • Rapid adsorption of cationic dye-methylene blue on the modified
           montmorillonite/graphene oxide composites
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Yang Yang, Weiye Yu, Shujun He, Shuaixian Yu, Ying Chen, Luhua Lu, Zhu Shu, Hongda Cui, Yong Zhang, Hongyun Jin Composite structure of montmorillonites(Mt)with graphene oxide (GO) or reduced graphene oxide (rGO) was successfully synthesized by grafting with 3-aminopropyl triethoxysilane (APTES) and hydrazine hydrate reduction. XRD, BET, FTIR, SEM and XPS analysis were used to characterize the surface and structure properties of the as-obtained products. Measurement results suggested that these two composites were similar in morphology and pore structure, but significantly different in the surface oxygenic groups. Adsorption properties of the Mt/GO and Mt/rGO were investigated using methylene blue (MB) as the target material. Compare to original Mt, APTES modified Mt and Mt/rGO, Mt/GO exhibited the highest adsorption capacity of 641.1 mg/g at the initial concentration of 750 mg/L, and MB was removed by 94.3% within 5min. Mechanism analysis suggested that the high absorption performance of the composite was determined by the high specific surface area, oxygenic groups of GO, high adsorption capacity of montmorillonite as well as the synergistic effect between the Mt and graphene oxide nanosheets.Graphical abstractUnlabelled Image
       
  • Modification of kaolinite from Pará/Brazil region applied in the anionic
           dye photocatalytic discoloration
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Joaldo da Silva Lopes, Wallonilson Veras Rodrigues, Vaeudo Valdimiro Oliveira, Aluska do Nascimento Simões Braga, Regiane Teixeira da Silva, Aline Aparecida Carvalho França, Edson Carvalho da Paz, Josy Anteveli Osajima, Edson Cavalcanti da Silva Filho The incorporation of titanium oxide and other transition metals on the surface of different materials has been shown to be a promising strategy to improve the of photocatalytic processes efficiency aiming at the decontamination of aqueous systems caused by persistent organic contaminants such as dyes. The objective of this work was to evaluate the catalytic properties of nanocomposites based on the kaolinite (Kaol) with TiO2 incorporated, obtained from the sol-gel method, used in discoloration of the coomasie brilliant blue dye (CBB) in aqueous solution. The nanocomposites were prepared from the reaction of titanium tetraisopropoxide with purified natural kaolinite and calcined at different temperatures. The samples were characterized by the XRD, FTIR, SEM-XED, BET-BJH and diffuse reflectance spectroscopy techniques, which demonstrated the structure, crystalline pattern, as well as the incorporation of titanium in the clay structure, changes caused by modification in morphology, texture and energy gap. The photocatalytic tests were performed using 5 × 10−5 mol L−1, 1.0 and 1.5 g L−1 concentration, respectively, to the CBB dye solution and to the synthesized materials. Among the nanocomposites, the sample calcined at 300 °C, KaolBT-300, presented the best photocatalytic performance. The addition of the H2O2 oxidant to the solution containing KaolBT-300 at the concentration of 1.5 g L−1 increased the discoloration percentage to 97.31% of the CBB solution dye after 120 min of irradiation. The discoloration kinetics of the CBB dye obeys the pseudo-first-order velocity law. Finally, the reuse of the KaolBT-300 sample in three consecutive cycles of photocatalysis demonstrated a significant adhesion stability of the TiO2 particles on the clay surface, indicating that it can be used in advanced oxidative processes for the degradation of organic pollutants.Graphical abstractUnlabelled Image
       
  • Effects of palygorskite on physical properties and mechanical performances
           of bone china
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Yuedan Zhang, Lijuan Wang, Fei Wang, Jianfeng Sun, Qingguo Tang, Jinsheng Liang In this work, the palygorskite with different contents upto 6 mass% was added into bone china bodies in order to improve the flexural strength, fracture toughness and thermal shock resistance of bodies. The phase composition and microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, the physical properties and mechanical performance of bone china were also studied. Results showed that the sintering temperature and thermal expansion coefficient (TEC) of bone china decreased with the increase of the addition amount of palygorskite. Specifically, adding 2 and 4 mass% palygorskite could improve the three-point flexural strength of bone china from 113 to 125.3 MPa and the fracture toughness from 2.11 to 2.21 MPa·m1/2, respectively. However, the flexural strength and fracture toughness of bone china were decreased along with the further increase of palygorskite addition. Moreover, the thermal shock resistance of bone china was improved from 160 °C to 180 °C via adding the palygorskite. The above findings provided a low-cost, simple and eco-friendly technique to improve the flexural strength, fracture toughness and thermal shock resistance of bone china.
       
  • Degradation of 2,4-dichlorophenol using palygorskite-supported bimetallic
           Fe/Ni nanocomposite as a heterogeneous catalyst
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Naeim Ezzatahmadi, Graeme J. Millar, Godwin A. Ayoko, Jianxi Zhu, Runliang Zhu, Xiaoliang Liang, Hongping He, Yunfei Xi A functional palygorskite-supported Fe/Ni (Pal-Fe/Ni) nanocomposite material is synthesised to remove 2,4-dichlorophenol (2,4-DCP) in an aqueous solution. The hypothesis is that Pal-Fe/Ni has superior efficacy than other Fe materials, such as Pal-Fe and Fe/Ni with regard to 2,4-DCP removal even though it requires less loading amount of metallic influencing the reaction. The surface morphology and surface chemical environments of Pal-Fe/Ni are studied using SEM, TEM, XRD and XPS characterisation methods. As revealed from batch experiments, initial pH, sample amount and reaction time are the key parameters influencing the 2,4-DCP removal efficiency. A further experiment reveals that iron leaching plays a main role for 2,4-DCP removal. Kinetic study reveals that removal of 2,4-DCP can be described by pseudo first-order model. A synergistic adsorption and catalytic reduction mechanism for the removal of 2,4-DCP by Pal-Fe/Ni is studied using UV–Vis, total organic carbon and HPLC-MS analyses. The results reveal complete dechlorination and 2,4-DCP degradation together with high total organic carbon removal. This study on immobilising Fe/Ni bimetallic nanoparticles onto palygorskite creates a new prospect for the practical application of Pal-Fe/Ni nanocomposite in remediation of contaminated aqueous solutions.Graphical abstractUnlabelled Image
       
  • Preparation of geopolymer inorganic membrane and purification of
           pulp-papermaking green liquor
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Meng-xue Xu, Yan He, Zi-han Liu, Zhang-fa Tong, Xue-min Cui This paper describes a low-cost and highly efficient metakaolin-based geopolymer composite membrane (support + dense layer) at normal pressure and
       
  • Influence of thermally modified clays and inexpensive pore-generating and
           strength improving agents on the properties of porous ceramic membrane
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Lorenna Alves Xavier, Thamayne Valadares de Oliveira, Walderson Klitzke, André Bellin Mariano, Daniel Eiras, Rafael Bruno Vieira The effect of the temperature of thermal treatment on the properties of ceramic membranes prepared from raw clays mixed with pore-generating and strength improving agents has been studied. Thermal treatment was performed at 500 °C (TC500) and 600 °C (TC600) and the properties of the membranes prepared from modified clays were compared with the properties of the membranes prepared from raw clay (NC). Three different additives were applied in the preparation of ceramic membranes; cationic manioc starch (CMS) was used as pore-generating agent, egg shell residue (ES) was used to improve mechanical strength and a mixture of ES/CMS was used to improve both porosity and mechanical strength of the ceramic membranes. Flat membranes were prepared from mixtures of thermally treated clays and additives with compositions of 5–15 wt% via uniaxial compression. The properties of tubular ceramics prepared by extrusion from samples NC and TC500 with ES/CMS of 5 wt% were evaluated in terms of hydraulic permeability, mechanical strength and apparent porosity using crossflow processes. The clays and their membranes were characterized by granulometric analysis, apparent porosity, three-point bending load experiments, X-ray fluorescence analysis, Fourier-transform infrared spectroscopy and X-ray diffraction experiments. The results show that the presence of thermally treated clays, independent of the type of pore-generating and mechanical strength improving agents, significantly improved the apparent porosity and hydraulic permeability, possibly due to opened pore structures. It is also suggested that the final performance is related to the structure of the clays, specifically to the presence of metakaolinite (MKaol). Besides, the addition of eggshell has increased the mechanical strength, possibly due to the increase of anorthite in the structure. Overall, these results demonstrate a potential application of thermally treated clays in development of porous ceramic membranes.
       
  • Hydraulic conductivity of geosynthetic clay liners to inorganic waste
           leachate
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Bao Wang, Jian Xu, Bin Chen, Xingling Dong, Tongtong Dou Hydraulic conductivity (k) tests were conducted to evaluate how the permeation of solidified/stabilized inorganic hazardous waste (SIHW) leachate affected the k values of two geosynthetic clay liners (GCLs): a natural sodium bentonite GCL (GCL-N) and a sodium-activated calcium bentonite GCL (GCL-S). The two GCLs were permeated with distilled water (DW) and a SIHW leachate. The effects of the type of bentonite, effective stress and prehydration were assessed. At effective stress of 30 kPa, the k to DW was 1.5 × 10–11 m/s and 5.1 × 10–11 m/s for GCL-N and GCL-S, respectively. In contrast, at the same effective stress, permeation with SIHW leachate caused the k to increase by factors ranging from 1.2 to 3733 for GCL-N and from 86 to 5294 for GCL-S, respectively. Compared with GCL-N, GCL-S had poorer hydraulic performance. Increasing the effective stress and prehydration with DW reduced the detrimental effect induced by permeation with SIHW leachate. Some GCL specimens maintained low k values to SIHW leachate even though the corresponding bentonites had small or modest swell indexes in SIHW leachate. The results of this study suggest that further evaluation is needed before using swell index test to assess the effect of SIHW leachate on the hydraulic performance of GCLs.
       
  • A contrastive study of effects of different organic matter on the smectite
           illitization in hydrothermal experiments
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Jiazong Du, Jingong Cai, Zewen Chen, Tianzhu Lei, Shoupeng Zhang, Zhonghuai Xie Although influence of organic matter (OM) on smectite illitization has received considerable attention in previous studies, the effect of different OM types on smectite illitization mechanism has rarely been examined. In the present study, hydrothermal experiments were conducted with N,N-dimethylhexadecylamine (16DMA)-smectite (M2) and lysine-smectite (M3) complexes to explore the effect of OM types on smectite illitization mechanisms. X-ray diffraction (XRD) analysis showed that mineral contents, illite percentage in mixed-layer illite-smectite (I% in ISm), the average number of layers (Nave), and stacking mode of ISm changed weakly at 300 °C. The changes varied obviously between M2 and M3 at>300 °C, indicating characteristics of solid-state transformation illitization mechanism in M2 and dissolution crystallization mechanism in M3. Moreover, the mid-infrared and thermo-XRD analyses indicated that the OM was mainly adsorbed in smectite interlayers at
       
  • A step ahead on efficient microwave heating for kaolinite
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): J.J. Reinosa, B. García-Baños, J.M. Catalá-Civera, J.F. Fernández The thermal evolution of kaolin clay under microwave radiation shows an unexpected large heating rate up to 500 °C/min for temperatures>650 °C. Such heating rate is associated with a resistivity drop of>103 Ω·m observed after the dehydroxylation process of the kaolin structure. The high efficiency of the microwave heating effect is correlated with the presence of surface carriers that absorbs microwaves electromagnetic field. The layered structure of the clay-based materials allows the appearance of charge carriers at the surface of the crystal lattice that is electromagnetically activated. This effect represents a breakthrough in the efficient use of microwaves energy in order to produce efficient thermal treatments in large volume of non-metallic minerals with a drastic reduction of the greenhouse gasses for mass production industries.
       
  • Mechanochemical activation of antigorite to provide active magnesium for
           precipitating cesium from the existences of potassium and sodium
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Zhiwu Lei, Xuewei Li, Pengwu Huang, Huimin Hu, Zhao Li, Qiwu Zhang Much attention has been paid to deal with cesium from the serious concern over the environmental threat as a well-known radionuclide. Radioactive cesium is usually precipitated and concentrated from aqueous waste before the final processing such as verification at high temperature for permanent storage underground somewhere. Few choices are available due to the high solubility of almost all the cesium compounds. A new idea is developed to use insoluble magnesium source to increase the efficiency of precipitating cesium as struvite (CsMgPO4.6H2O). Activated antigorite (Mg3Si2O5(OH)4) by ball-milling was used together with phosphoric acid to combine cesium chloride and form struvite at nearly stoichiometric ratio, even by simple agitation at room temperature. It is more interesting to notice that other alkali metals of potassium and sodium do not form stable struvite phase and remain in solution, giving a very high selectivity of cesium removal over potassium and sodium. This method may be applied both in cesium removal from the radioactively contaminated source and cesium concentration for metallurgical processing.Graphical abstractUnlabelled Image
       
  • 3D-microstructure analysis of compacted Na- and Cs-montmorillonites with
           nanofocus X-ray computed tomography and correlation with macroscopic
           transport properties
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Hiroaki Takahashi, Yukio Tachi Microstructural and mass transport properties of compacted Na- and Cs-montmorillonites (Na-MMT and Cs-MMT) with different swelling properties at dry densities of 0.8 and 1.25 Mg m−3 were investigated by combining three-dimensional microstructure analysis using nanofocus X-ray computed tomography (CT), X-ray diffractometry (XRD), and through diffusion measurement of deuterated water (HDO). The X-ray CT and XRD observations indicated that macropores (micrometer- and submicrometer-sized pores) in the dry state of compacted Na-MMT are filled with gel phases, and the grain sizes of clay particles shifted toward smaller values through the saturation and swelling processes. By contrast, no gel phase and no decrease in the grain and pore volumes were observed for saturated Cs-MMT. The De of HDO of Na-MMT was reduced by half compared to that of Cs-MMT owing to the high swelling capacity of Na-MMT and the occupation of macropores with gel phases. The geometrical factors of the macropores, including tortuosity (τ) and geometric constrictivity (δg), in the dry and saturated states of compacted Na-MMT and Cs-MMT were estimated from three-dimensional images of the macropores (and gel phases in saturated Na-MMT) and from the results of their statistical analysis. The estimated geometric factor (δg/τ2) of saturated Cs-MMT was consistent with the corresponding De/εD0 values derived in the HDO diffusion experiment. In the case of Na-MMT, the larger differences between the geometric factors (δg/τ2) evaluated by nanofocus X-ray CT and the De/εD0 values derived by the diffusion tests can be explained by the electrostatic constrictivity factor and the additional geometrical factors in gel phase and interlayer that are smaller than the detection limit of the nanofocus X-ray CT.
       
  • Effect of layer-by-layer self-assembled sepiolite-based nanocoating on
           flame retardant and smoke suppressant properties of flexible polyurethane
           foam
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Ying Pan, Longxiang Liu, Wei Cai, Yuan Hu, Shudong Jiang, Hongting Zhao In this study, a facile and water-based route was developed for fabricating flame retardant and smoke suppressant flexible polyurethane foam (FPUF). FPUF was deposited with a multilayered coating by layer-by-layer (LbL) self-assembled method, which was composed of the positively charged polyethyleneimine (PEI) and negatively charged alginate and sepiolite. The prepared coatings were shown to be successfully constructed on the surface of FPUF, as characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Subsequently, the combustion behavior of FPUF was evaluated by cone calorimeter. Results showed that, with 6 bilayers PEI/sepiolite + alginate coating, the peak heat release rate and total heat release of PU-6 were reduced 76% and 27%, respectively, as compared with those of untreated sample. Meanwhile, the deposited coating could effectively reduce the smoke production of FPUF, as evidenced by the remarkable reduction of smoke production rate and total smoke production for the treated FPUF.
       
  • Development of broad-acting clays for the tight adsorption of
           benzo[a]pyrene and aldicarb
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Meichen Wang, Sara E. Hearon, Natalie M. Johnson, Timothy D. Phillips People and animals can be unintentionally exposed to complex mixtures of hazardous chemicals that can threaten the safety of food and water supplies following natural and man-made disasters and emergencies. Our research has focused on the development of broad-acting adsorbents that will tightly bind environmental contaminants in the gastrointestinal tract and decrease their bioavailability to humans and animals during these events. In this study, benzo[a]pyrene (BaP) and aldicarb were used as representative chemicals due to their high toxicity and extensive distribution in the environment. Both chemicals have been commonly detected in water and sediments in the US, and their distribution and concentrations can be enhanced during disasters. To address this problem, we have amended and functionalized montmorillonite clays with the nutrients, l-carnitine and choline to enhance their attraction for lipophilic toxins, such as BaP and aldicarb. Based on equilibrium isothermal analyses, we have demonstrated a significantly increased binding capacity (Qmax) and affinity (Kd) for BaP and aldicarb compared to the parent clay. Adsorption isotherms also showed that talc bound strongly to BaP with the highest Qmax, which was twice that of activated carbon. Additionally, cultures of adult hydra with a metabolism activation package were used as an in vivo toxicity indicator to confirm the ability of test adsorbents to protect against toxicity at low inclusion levels. We anticipate that the optimal adsorbents developed can be delivered in food and flavored water, or administered by sachet or capsule during emergencies and disasters to decrease human and animal exposures to environmental toxins.Graphical abstractUnlabelled Image
       
  • A novel magnetic heterogeneous catalyst based on decoration of halloysite
           with ionic liquid-containing dendrimer
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Samahe Sadjadi, Masoumeh Malmir, Majid M. Heravi A magnetic catalyst is synthesized through growth of dendrimer of generation 3 (G3) on the surface of halloysite (Hal) nanotubes followed by decoration of dendrimer terminal groups with ionic liquid (IL) and incorporation of Fe species. The structure of the catalyst was confirmed by using several characterization techniques. Moreover, the catalytic activity of the catalyst for oxidation of benzaldehydes to the corresponding benzoic acids in the presence of hydrogen peroxide was investigated. Notably, to improve the yield of the reaction, β-cyclodextrin (β-CD) was employed as phase transfer agent. The contribution of dendrimer and IL to the catalysis was confirmed by comparing the catalytic activity of the catalyst with that of control the catalysts (the catalyst without IL, Fe species and dendrimer). Furthermore, the effect of dendrimer generation was elucidated by comparing the catalytic activities of the catalysts prepared by growth of dendrimers of G1, G2 and G3 on Hal. Studying the recyclability of the catalyst, it was found that the catalyst could be recovered and recycled for several reaction times with slight loss of leaching of Fe species.Graphical abstractUnlabelled Image
       
  • Cetylpyridinium bromide-modified montmorillonite as filler in low density
           polyethylene nanocomposite films
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Cristina Muñoz-Shugulí, Francisco J. Rodríguez, Julio E. Bruna, María J. Galotto, Claire Sarantópoulos, Mary A. Favaro Perez, Marisa Padula The development of clay polymer nanocomposites has been presented as an interesting alternative for design of new active food packaging materials. In this work, low density polyethylene (LDPE) nanocomposites with cetylpyridinium bromide (CPB) – modified montmorillonite (Mt) were developed. In a first stage, Mt. was modified with different CPB proportions based on cation exchange capacity (1:1 and 2:1), resulting in two different organoclays. These modified clays were hydrophobic and presented a good thermal stability that favored their capacity for extrusion to develop LDPE nanocomposites. Based on the incorporated organoclay, nanocomposite films showed important changes in morphology, and differences in mechanical properties, crystallinity, and gas permeability in comparison to polyethylene. All nanocomposites showed greater opacity than LDPE, however, their color changes did not exceed the visual perception limit. Finally, electrical conductivity (EC) measurements showed that CPB was able to migrate from the nanocomposite films to an aqueous food simulant. This behavior was dependent on the availably of free CPB in the matrix, its disposition in the organoclay and the organoclay distribution into the polymer matrix. These results highlight the migration of the surfactant from LDPE nanocomposites with Mt./CPB organoclays, making montmorillonite a potential surfactant carrier that increases compatibility and function in polymers allowing the generation of novel materials that could be used in the design of food packaging.Graphical abstractUnlabelled Image
       
  • Novel hierarchically porous allophane/diatomite nanocomposite for benzene
           adsorption
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Liangliang Deng, Peixin Du, Wenbin Yu, Peng Yuan, Faïza Annabi-Bergaya, Dong Liu, Junming Zhou Allophane/diatomite (Allo/Dt) nanocomposite with a hierarchically porous structure was prepared via an in situ hydrothermal method. This hierarchically porous structure consists of i) micropores remaining from the initial stacked coating allophane particles; ii) mesopores formed by the transformation of the macropores of diatom frustules due to the filling of allophane particles in the inner walls, and iii) preserved macropores of diatom frustules. The coating amount of allophane particles in Allo/Dt nanocomposite was 59.1%, leading to a specific surface area of 155.9 m2/g, which was substantially higher than that of diatomite (17.9 m2/g). The benzene adsorption performance and related adsorption mechanisms of Allo/Dt nanocomposite were investigated. The larger benzene dynamic adsorption capacity of 121.6 mg/g, compared to that of the synthetic allophane (105.9 mg/g), resulted from the adequate adsorption space provided by the hierarchically porous structure. Moreover, Allo/Dt nanocomposite displayed a higher efficiency for benzene adsorption in mesopores of the coating allophane particles because of their improved dispersity. These results demonstrated that the fabrication process of Allo/Dt nanocomposite can overcome not only the aggregation of allophane but also diatomite's shortcoming of low specific surface area, making the nanocomposite to be a promising adsorbent for the treatment of volatile organic compounds.
       
  • Facile fabrication of the polyaniline/layered double hydroxide nanosheet
           composite for supercapacitors
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Xi Cao, Hong-Yan Zeng, Sheng Xu, Jian Yuan, Jing Han, Gao-Fei Xiao To overcome the structural instability of polyaniline (PANI) due to repeated volumetric swelling and shrinking during charge/discharge process, the LDH/PANI composite was designed and prepared via the assembly of organic PANI and 2D host nanosheets from the MgFe layered double hydroxide (MgFe-LDH) through incorporation of PANI between the nanosheets gap using in situ polymerization. Owing to the combined advantages of conducting PANI and 2D nanosheets, the LDH/PANI composite exhibited excellent supercapacitive performance, including low resistance, high specific capacitance, good charge/discharge stability and long-term cycling life, which greatly improved faradaic redox reaction and mass transfer. As electrode material for supercapacitors, the LDH/PANI composite showed a maximum specific capacitance of 592.5 F·g−1 at a current density of 2 A·g−1, and achieved remarkable capacitance retentions of 87% after 500 cycles. The LDH/PANI material may be a potential economical alternative electrode material for supercapacitors.
       
  • Halloysite based nanocomposites and photocatalysis: A Review
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): D. Papoulis Heterogeneous photocatalysis is an efficient, relatively cheap and environmentally friendly technology for decomposing various organic and air pollutants. Halloysite is a natural clay mineral usually in the form of nanotubes that has many applications as well as potential uses including photocatalysis. In this paper the photocatalytic activities of halloysite-based nanocomposites in combination with various photocatalysts that have been synthesized and tested in decomposing organic and air pollutants are reviewed. Many photocatalysts have been synthesized and among them TiO2 in the form of anatase, or rutile, or a mixture of both is the most common photocatalyst due to its effectiveness and low cost. Researches by many investigators are summarized and discussed. The possibilities and limitations of halloysite-based nanocomposites for future applications are also discussed and new fields of research are proposed. It is suggested that Halloysite-based nanocomposites are more promising in positively charged organic substrates like tetracycline and Rhodamine B where the organic pollutant is attracted by halloysite's negatively charged external surfaces close to the photocatalysts, than neutral like paracetamol or negatively charged which that attraction does not occur.Graphical abstractSchematic representation of preparation of HNTs-TiO2 nanocomposites and TEM images of TiO2-HNTs.Unlabelled Image
       
  • Acid activated montmorillonite for gas-phase catalytic dehydration of
           monoethanolamine
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Gui-Qiu Huang, Yong-Hong Song, Chang Liu, Jian-Ming Yang, Jian Lu, Zhao-Tie Liu, Zhong-Wen Liu The acid activated montmorillonite (Acid-Mt) was investigated for the first time as a catalyst for the gaseous-phase dehydration of monoethanolamine (MEA). A series of Acid-Mt was obtained by treating the Na-type montmorillonite (NaMt) at 104 °C in 3.2 mol L−1 HNO3 aqueous solution for 4–24 h followed by calcining at 450–1150 °C for 4 h, respectively. The Acid-Mts were characterized by X-ray diffraction, temperature programmed desorption of NH3, temperature programmed desorption of CO2, and N2 adsorption-desorption, and were evaluated as catalysts for the gaseous-phase dehydration of MEA. With increasing the activation time or calcination temperature, both the amounts of acidic and basic sites over Acid-Mt were decreased, and more pronounced extent was observed in the case of changing the calcination temperature. By correlating the catalytic results with the characterization results, the acidity of the catalyst was revealed to be the key factor in determining the MEA conversion. In contrast, a complex picture was observed in the case of the product selectivity. Generally, a higher acidity over Acid-Mt favored the intermolecular dehydration and 1,2-elimination reactions of MEA, leading to a higher selectivity of piperazine (PIP) and triethylenediamine (TEDA). When the acidity of Acid-Mt was lower, the intramolecular dehydration and deamination reactions were improved resulting in an increasing selectivity of ethyleneimine (EI). Importantly, the product distribution of the MEA dehydration was greatly regulated by the simply changing the acid activation parameters of Mt. Thus, Acid-Mt is a promising catalyst for selectively synthesizing different N-containing fine chemicals via the MEA dehydration reaction.Graphical abstractUnlabelled Image
       
  • Cationic and anionic clay nanoformulations of imazamox for minimizing
           environmental risk
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Rachid Khatem, Rafael Celis, M. Carmen Hermosín A synthesized anionic clay (layered double hydroxide or LDH) and a commercial cationic organoclay (Cloisite 10A, Clo10A) were assayed as host nanocarriers for imazamox (Imz) herbicide. Imz-LDH complexes were obtained by direct synthesis (DS) and regeneration (RE), whereas Imz-Clo10A complexes were prepared by ground mixing (GM) and through methanol addition (weak [WC] and strong [SC] complexes). Characterization of the complexes showed that Imz was partially hosted in the interlayer structure of the resulting nanoherbicides, as anion or as neutral molecule, with some of the herbicide at the external surfaces, depending on the carrier and preparation. The nanoherbicides showed a total water release from 73 (Imz-LDH DS) to 98% (Imz-Clo10A GM) with an immediate release from 67 (Imz-LDH DS) to 93% (Imz-Clo10A GM), while technical Imz released instantaneously>98%. The herbicide maximum concentration in the leachates from Imz-treated soil columns decreased between 20 and 35% for nanoherbicides with respect to the technical Imz, and between 10 and 30% with respect to a commercial Imz formulation. Total herbicide soil leaching losses were reduced from 95 or 98%, for technical and commercial Imz, to 77–67% for nanoherbicides. Bioassays showed similar efficacy for nanoherbicides and commercial product. The diverse Imz-clay complexes are revealed as smart delivery systems for this systemic herbicide by decreasing Imz water pollution risk while maintaining efficacy, with the advantages of their soil compatible matrix and the possibility to be located at action point in the subsoil.Graphical abstractUnlabelled Image
       
  • Thermal behavior of samarium oxide – Ball clay mixtures for high
           macroscopic neutron capture cross section ceramic materials
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): M.S. Herrera, M.F. Hernández, M. Cipollone, M.S. Conconi, N.M. Rendtorff The effect of the addition of samarium oxide (Sm2O3) in the thermal behavior of (66%) kaolinitic ball clay was studied and compared with the pure clay.The incorporation of Sm2O3 is of technological interest for the design of smart traceable ceramic proppants used for unconventional gas and oil well stimulation. These high macroscopic neutron capture cross section proppants are used to obtain relevant information, such as the location and height of the created hydraulic fractures, through a neutron based detection technology.The study comprised a set of thermal analysis up to 1400 °C and the sintering behavior of the clay, up to 5% of addition. The developed texture and microstructure was also assessed. A simple mechanical characterization was performed as well.No important effects in kaolinite dehydration temperature (500–600 °C); and mullites formation (primary and secondary) were observed (990 and ≈1200 °C). The sintering range of the studied clay is 1080–1360 °C; the 5% wt. addition resulted in 80 °C decrease of the final sintering temperature, due to the more active flux nature of the added oxide.Mixtures fired at 1250 and 1400 °C resulted in dense ceramic materials with mullite as principal crystalline phase accompanied by quartz and cristobalite; imbibed in a viscous glassy phase which was proportionally increased by the added oxide. The mullite content and cell parameters were not affected. No samarium containing binary or ternary crystalline phases were detected, inferring that the rare earth is dissolved by the active viscous glassy phase thermally formed from the clay crystalline phases. No significant effect was observed in the spherical diametral compression test.Low concentration addition of the oxide did not affect the porosity or water absorption of the developed ceramics. Only the 5% wt. addition resulted in a noticeably higher de-sinterization with the appearance of macro-porosity if fired at 1400 °C.
       
  • Modification, hybridization and applications of saponite: An overview
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Chun Hui Zhou, Qian Zhou, Qi Qi Wu, Sabine Petit, Xue Chao Jiang, Shu Ting Xia, Chun Sheng Li, Wei Hua Yu Modification of saponite (Sap) by surface engineering and intercalation chemistry introduces guest species into the structure of Sap and enhances the functionalities of the resultant Sap-based hybrids or composites. This review summarizes and evaluates latest scientific advances in the strategies for surface engineering, intercalation and hybridization of Sap, the insights into the relevant mechanisms, and the properties and applications of the resultant Sap-based materials. Studies have indicated that Sap can be inorganically modified by acid activation, inorganic cation exchange, pillaring, and adsorption. The methods of preparing organo-saponite (OSap) hybrids can be categorized as follows: 1) exchanging the inorganic cations in the interlayer space of Sap with organic cations; 2) covalent grafting of organic moieties or groups onto the surface of Sap; 3) intercalating polymer into the interlayer space of Sap by solution intercalation, and melt mixing or in situ polymerization. Organic-inorganic modified Sap can be made through the reactions between organic species and inorganic-modified Sap, or by the combination of inorganic species with organic-modified Sap. Modified Sap exhibits exceptional thermal stability, surface acidity, optical effects and adsorption. As such, the modified Sap can be used for optical materials, adsorbents, catalysts and clay/polymer nanocomposites (CPN). Literature survey suggests that future studies should place emphasis on optimizing and scaling up the modification of Sap, probing the thermodynamics, kinetics and mechanisms of the modification of Sap, endowing Sap with novel functionalities, and accordingly advancing the practical applications of the resultant Sap-based materials.Graphical abstractUnlabelled Image
       
  • Wastewater treatment test by removal of the sulfamethoxazole antibiotic by
           a calcined layered double hydroxide
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): El Hassane Mourid, Mohamed Lakraimi, Lhaj Benaziz, El Hassan Elkhattabi, Ahmed Legrouri In this study, we investigated the removal of the sulfamethoxazole drug (SMX) by calcined layered double hydroxides (CLDHs) at 500 °C. The characterization of the fresh CLDH solids and after removal of SMX, by X-ray diffraction, infrared spectroscopy and scanning electron microscopy, shows that the removal is carried out by reconstruction of LDH phases intercalated by SMX via the memory effect of mixed oxides. The thermodynamic parameters indicate that the adsorption is governed by physisorption.The removal capacity of SMX by CLDHs, under optimal conditions, reaches 4314 mg/g with an SMX/CLDH mass ratio of 1.6 and the elimination rate reaches 93%. This result is a good sign for fighting the development of bacterial resistance to such antibiotics because the quantity that may remain in natural environments is very low. Recycling of the intercalated phases remains efficient after six cycles.Graphical abstractUnlabelled Image
       
  • Clay-based electrospun nanofibrous membranes for colored wastewater
           treatment
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Seyed Abolhassan Hosseini, Manouchehr Vossoughi, Niyaz Mohammad Mahmoodi, Mohtada Sadrzadeh Novel montmorillonite (Mt) chitosan/poly(vinyl alcohol) (PVA) nanocomposite electrospun nanofibrous membranes (ENM) were prepared and utilized for the treatment of colored wastewater. The Mt. with different mass percentages (0, 1.0, 2.0 and 3.0 mass%) was added to the membrane structure, and its effect on morphology, pore size, porosity, mechanical strength, and permeation properties of ENM were investigated. The fabricated membranes were used as affinity membranes for dye removal with ultrafast permeating adsorption. The results showed that incorporating Mt. as a reinforcing agent improved the nanocomposite ENM resistance to compaction. Young's modulus for the prepared membranes increased from 0.89 MPa for chitosan/PVA ENM to 2.09 MPa for a nanocomposite ENM containing 1.0 mass% of Mt. The optimum concentration of Mt. that increased both water flux and dye removal was found to be 2.0 mass%. The optimized membrane provided 95% rejection of Basic Blue 41 (BB41) with a significantly high flux of 1765 L/m2 h under 0.4 bar operating pressure, effectively overcoming the trade-off between permeability and selectivity. Moreover, the prepared nanoclay-based ENM was found to be antifouling and reusable for several cycles of dye removal.
       
  • Effect of γ-manganite particle size on Zn2+ coordination environment
           during adsorption and desorption
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Zhangjie Qin, Fan Liu, Shuai Lan, Wei Li, Hui Yin, Lirong Zheng, Qin Zhang The nanostructured manganese oxyhydroxides are great importance in controlling the environmental pollution. Here we investigated the properties of γ-manganite (γ-MnOOH) having two different particle sizes and their effects on Zn2+ coordination during adsorption and desorption, using a combination of X-ray diffraction analysis, thermal gravimetry, pore structure analysis, high-resolution transmission electron microscopy, acid-base titration and X-ray absorption spectroscopy. The small-particle-sized (SPS) γ-MnOOH with short aging time has a low degree of crystallinity, a large specific surface area, a low point of zero change and a low structural stability relative to the big-particle-sized (BPS) one. Comparison of natural sample with synthetic γ-MnOOH by atom distances indicates that the growth force along [11-1] direction is larger than that along [101] direction, although the particle size along the former direction is much smaller. Regarding the adsorption and desorption of Zn2+, the SPS γ-MnOOH has a higher adsorption density and lower desorption percentage than the BPS one under the same condition. Based on the desorption of Zn2+ adsorbed in corner-sharing linkage on γ-MnOOH surface, the linear combination fitting results indicate that, Zn2+ is mainly desorbed as Zn2+ four-fold coordination (ZnO4) complexes for low initial concentration of Zn2+ ([Zn]initial) and as Zn2+ six-fold coordination (ZnO6) complexes for high [Zn]initial; SPS γ-MnOOH has a higher ZnO4 percentage than the BPS one. The compensating charge capacity of ZnO6 and ZnO4 complexes in γ-MnOOH may increase in the linkage order: ZnO6-corner-sharing 
       
  • Facile preparation of an efficient flame retardant and its application in
           ethylene vinyl acetate
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Jin-Ze Du, Li Jin, Hong-Yan Zeng, Bo Feng, Sheng Xu, En-Guo Zhou, Xiao-Kun Shi, Lu Liu, Xi Hu A novel phosphorus-nitrogen-clay flame retardant (PD-LDH@MF) was prepared via intercalating pentaerythritol diphosphate (PEDP) into MgAl hydrotalcite (LDH) interlayers and then capping melamine resin (MF) on the surface using in-situ copolymerization. The structure, morphology thermal stability and flame retardancy of the PD-LDH@MF material were characterized by various analytic methods. The results revealed that PEDP anions were intercalated successfully into the interlayers of the LDH, and the PEDP-intercalated LDH (PD-LDH) was also encapsulated in MF. The PD-LDH@MF exhibited better compatibility with EVA matrix than the EVA/PD-LDH due to higher hydrophobicity by capping MF on the surface of the PD-LDH particles. The incorporation of the PD-LDH@MF into EVA could improve not only the thermal stability but also the thermal oxidative resistance for EVA matrix. The limiting oxygen index (LOI) of the EVA/PD-LDH@MF composite with 15 wt% loading was about 27.5%, while the composite attained V-0 rating. The observable improvement in flame retardancy of the EVA/PD-LDH@MF composite was because intercalated PEDP could promote to remain more N and C elements, and P species in PEDP participated into the connecting reaction to form the more continuous and more compact char layer on the char surface, thus hindering heat diffusion and oxygen transmission effectively.Graphical abstractUnlabelled Image
       
  • Genesis of the Eastern Iranian bentonite deposits
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Soroush Modabberi, Alireza Namayandeh, Massimo Setti, Alberto López-Galindo Numerous bentonite deposits are located in Southern Khorasan (Eastern Iran), especially in Ferdows and Sarayan counties. We studied the genesis of these bentonites at seven deposits (Chah-Taleb, Chah-Keshmir, Chah-Golestan, Chah-Pirouz, Gholeh-Gelia, Kharman-Sar and Khal-Kooh) using petrological, mineralogical and geochemical data (including X-ray diffraction and fluorescence, and inductively coupled plasma-mass spectrometry) from both bentonites and parent rock samples. The deposits mainly consist of Na-montmorillonite and opaline silica, with lesser amounts of quartz, feldspars, carbonates, halite, zeolites, and illite. The studied deposits formed in a volcanic arc setting and their magma series are calc-alkaline, except for the Kharman-Sar deposit, which is tholeiitic in composition. The presence of significant amounts of opaline silica indicates a low fluid flow rate in these systems, in spite of the high leaching of alkalis.The strata-bound nature of the studied deposits, as well as the high amount of montmorillonite, the presence of gypsum layers alternating with those of bentonite and the lack of hydrothermal alteration suggest that these Iranian bentonite deposits were formed through diagenetic processes in lagoon environments, by means of the alteration of intermediate to acidic precursors, trachy-andesite to rhyolite, belonging to two volcanic provinces: one pyroclastic realm in Ferdows, and another volcaniclastic in Sarayan.
       
  • Effect of a calcined Westerwald bentonite as supplementary cementitious
           material on the long-term performance of concrete
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): A. Trümer, H.-M. Ludwig, M. Schellhorn, R. Diedel The objective of using supplementary cementitious materials (SCMs) in cement is to reduce costs and the overall CO2 output of the cement production. Against the background of an increasing demand for cement and a decreasing availability of common SCMs, calcined clays serve as alternative material for the industrial-scale manufacture of composite cements. In the presented study, a raw bentonite clay of high volume capacity and small exploitation options was selected to check its pozzolanic activity after suitable thermal treatment and the consequent effects on the concrete performance. The results show that, at high cement substitution rates of 30%, the properties of the concrete were not changed to a significant extent. In certain durability issues namely sulphate resistance, inhibition of alkali silica reaction (ASR) and chloride migration, the mixture with calcined clay even performed better than the reference. Other properties like final strength and frost and de-icing salt resistance were changed in an uncritical way. Negative effects were observed on the early strengths and on the carbonation velocity. However, giving careful consideration to these aspects during concrete projecting, the calcined clay would be a suitable material for the majority of concrete applications.
       
  • Determination of half maximal inhibitory concentration of CaAl layered
           double hydroxide on cancer cells and its role in the apoptotic pathway
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Arnab Bhattacharjee, Sk Hasanur Rahaman, Suman Saha, Monisha Chakraborty, Jui Chakraborty In continuation of our previous work, which proposed a new direction of application of the bare, phase pure CaAl LDH as an active anticancer agent, the efficacy of the system was assessed by determination of half maximal inhibitory concentration (IC50) of the same on human colon cancer (HCT 116) cell line and human breast cancer (MCF 7) cell line. This was in turn established by tracing the involvement of Ca2+ ion with the CAMKIIα protein- a key player in the Ca2+/Calmodulin pathway which remains overexpressed in human colon cancer cell. CAMKIIα regulates the reactive oxygen species (ROS) production by decreasing the activity of superoxide dismutase (SOD) enzyme and hence SOD activity was also evaluated in our study. The results exhibit significant involvement of the bare, phase pure CaAl LDH at cellular level to down regulate CAMKIIα and SOD gene and its active involvement in apoptosis could also be traced.
       
  • Critical review of montmorillonite/polymer mixed-matrix filtration
           membranes: Possibilities and challenges
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Derrick S. Dlamini, Jianxin Li, Bhekie B. Mamba This paper reviews the literature on clay/polymer (CP) based mixed-matrix membranes (MMM) for water treatment. Clay minerals have been credited for ultrafiltration (UF) membranes behaving like nanofiltration (NF) membranes in terms of salt rejection through the repulsion mechanism. This is interesting and more attention should be focused on this approach. There is an apparent agreement in the literature that the observed increase and then decrease in water flux with an increase in clay mineral loading is a result of viscosity changes in the casting solution. While this is true, there is still a need for studies that will consider that the clay mineral sheets are much larger compared to water molecules and are impermeable; hence, at higher loading they may impede water flow. Exfoliated clay platelets are basically similar to graphene oxide, which has gained significant attention lately in water treatment studies; however, to date, there is no information on the effect of the delaminated structures on the performance of available CP membranes.
       
  • Effect of surfactant on thermo-physical properties and spray cooling heat
           transfer performance of Cu-Zn-Al LDH nanofluid
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Samarshi Chakraborty, Iman Sengupta, Ishita Sarkar, Surjya K. Pal, Sudipto Chakraborty The focus of the present study is to investigate the effect of surfactant addition on thermo-physical properties, stability, and heat transfer performance of Cu-Zn-Al LDH nanofluid. For this purpose, both an anionic (Sodium dodecyl Sulfate (SDS), concentration: 200–800 ppm) and a non-ionic surfactant (Tween 20, concentration: 28–70 ppm) have been used at different concentrations with Cu-Zn-Al LDH nanofluid at a fixed concentration. Among both the surfactants, SDS displayed better compatibility and thermo-physical properties when combined with Cu-Zn-Al LDH nanofluid compared to LDH-Tween 20 combination. The addition of both the surfactants into the nanofluid suspension has led to reduced surface tension and viscosity value which is highly desired for better wettability and improved contact between the coolant and the hot surface. The maximum increment in thermal conductivity value was attained in the case of Cu-Zn-Al LDH at 600 ppm SDS concentration which is 20.9% higher than the water. In terms of stability analysis, the highest zeta potential value of −52.7 mV was also observed for Cu-Zn-Al LDH at 800 ppm SDS loading. The highest cooling rate of 174.8 °C/s was attained by Cu-Zn-Al LDH-SDS (600 ppm) nanofluid which is 30.7% higher than what had been achieved by water based cooling. However, the use of Tween 20 in LDH nanofluid has displayed detrimental impact on poor thermal conductivity, zeta potential, and heat transfer results for the LDH nanofluid.Graphical abstractUnlabelled Image
       
  • MgAl-LDH/Biochar composites for methylene blue removal by adsorption
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): L. Meili, P.V. Lins, C.L.P.S. Zanta, J.I. Soletti, L.M.O. Ribeiro, C.B. Dornelas, T.L. Silva, M.G.A. Vieira In this work, LDH-biochar composites were synthesized in different molar ratios of Mg:Al (2:1, 3:1 and 4:1) using co-precipitation method. The composites were applied to remove an organic dye from aqueous solutions by adsorption. The composites and the pure bovine bone biochars were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurements, thermogravimetric analysis (TG/DTG), dispersive energy spectroscopy (DES) and scanning electron microscopy (SEM). The methylene blue dye adsorption experiments were conducted in a finite bath. The results indicate that pH 12 is more suitable for dye adsorption process, with a removal>95% for all composites. The adsorption kinetic was best described by the pseudo-second order model, reaching the equilibrium in approximately 20 min. The Redlich-Peterson model fit the adsorption equilibrium isotherms satisfactorily. It was obtained a maximum adsorption capacity of 406.47 mg·g−1 at 40 °C. Negative values of ΔG indicate the spontaneity of the adsorption process. The positive value of ΔH (30.72 kJ·mol−1) indicates the physical nature of the adsorption and the positive value of ΔS (0.1863 kJ·mol−1) indicates that there was a change in the structure of the adsorbent and increased randomness during the fixing of the dye.
       
  • Effective degradation of methylene blue in aqueous solution using
           Pd-supported Cu-doped Ti-pillared montmorillonite catalyst
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): Annu Joseph, Kannan Vellayan, Beatriz González, Miguel A. Vicente, Antonio Gil The effluents from the textile, paper and food industries contain organic dyes that are strongly colored and reveal harmful effect on living systems. In order to reduce water pollution, the degradation of dye into non toxic form is desirable. Methylene blue is one such organic dye, discharged from textile industries. In this work, the catalytic degradation of methylene blue was investigated using a montmorillonite supported trimetallic catalyst, prepared by supporting Pd on a Cu-doped Ti pillared montmorillonite. The catalyst exhibited excellent performance to reduce methylene blue, in the presence of NaBH4. The decolorization was appreciable and the results indicated that methylene blue could be successfully decolorized and degraded using the catalyst under room conditions. Almost complete degradation was achieved within 20 min. The results obtained were better than those reported for other catalysts.
       
  • An experimental study on smectites as nitrogen conveyors in subduction
           zones
    • Abstract: Publication date: February 2019Source: Applied Clay Science, Volume 168Author(s): D.G. Cedeño, R.V. Conceição, M.R.W. Souza, R.V.S. Quinteiro, L.C. Carniel, J.M.M. Ketzer, F. Rodrigues, E.C. Bruzza We performed high pressure and high temperature (HPHT) experiments on NH4-doped montmorillonite (~2 wt% of NH4) under pressures of 2.5, 4.0, and 7.7 GPa and temperatures from 200 to 700 °C. Each experiment was analyzed with XRD, FTIR, CHN elemental analysis, and SEM in order to determine the NH4-Smectite phase changes and their morphology, and the presence of ammonium in the runs. Our results show that smectite can easily transport nitrogen, speciated as ammonium (NH4+), incorporated into the smectite interlayer in mildly reducing environments to deeper levels in the Earth through cold thermal regime subduction zones. NH4-Smectite transforms into NH4-enriched micaceous phase (tobelite) through a NH4+-enriched interlayered I/S phase in relatively low pressures and temperatures (around 2.5 GPa and 500 °C). Tobelite is stable until more extreme conditions (7.7 GPa and 700 °C), together with lesser amounts of buddingtonite (an ammonium-bearing feldspar) kyanite, and garnet. Our experiments also show the effect of nitrogen in the feldspar stability, as potassic and sodic feldspar are stables until ~5 GPa, while buddingtonite, is stable at 7.7 GPa. Nitrogen can return to the surface once the stability of these nitrogen-enriched minerals is reached due to pressure or temperature increasing.
       
  • A comparative study of different natural palygorskite clays for
           fabricating cost-efficient and eco-friendly iron red composite pigments
    • Abstract: Publication date: Available online 23 October 2018Source: Applied Clay ScienceAuthor(s): Yushen Lu, Wenkai Dong, Wenbo Wang, Qin Wang, Aiping Hui, Aiqin Wang A series of α-Fe2O3/palygorskite (α-Fe2O3/Pal) inorganic-inorganic composite pigments were prepared by a one-step hydrothermal process using six kinds of iron-rich natural palygorskite clays (Pal-c) with different structures, morphologies and compositions as starting materials. The effects of different natural Pal-c on the structure, chemical composition, color and stability of the as-prepared composite pigments were studied comparatively by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmittance electron microscope (TEM), X-ray fluorescence spectroscopy (XRF) and CIE-L*a*b* colorimetric analyses. The results showed that the Fe(III) ions in the reaction solution can be converted into red α-Fe2O3 particles in situ on the Pal surface, without adding any chemical precipitant. Pal not only induce formation of α-Fe2O3 as a ‘green’ precipitant, but also effectively control the particle size of α-Fe2O3 nanoparticles as a microreactor and prevent the aggregation of particles as a supporter. The chemical composition of natural Pal-c has a great influence on the L*, a*, b* values of the composite pigments, while the associated mineral types have little effect on the color values of the pigments. The optimal iron-red composite pigment mainly composed of 58.59% Fe2O3 and 35.11% SiO2 exhibits the best L* value of 31.1 and a* value of 33.4, which is superior to commercial iron red pigment (a* = 26.9). The red composite pigment exhibits excellent chemical stability and remains in a good red color after treatment with an acid solution, an alkaline solution, or an organic solvent. In addition, the red composite pigment can be well dispersed in ethanol or water, and can be uniformly sprayed onto the ceramic substrate and stably coated on it, and remains a vivid red color after calcinations at 1100 °C.Graphical abstractUnlabelled Image
       
  • Electrophoretic deposition of bioactive glass-nanoclay nanocomposites on
           titanium
    • Abstract: Publication date: Available online 15 October 2018Source: Applied Clay ScienceAuthor(s): U. Mehana Usmaniya, V.V. Anusha Thampi, B. Subramanian Nanopowders of 45 s5 bioactive glass were synthesized by simple sol-gel technique. The powder was characterized for their microstructure and morphology. X-ray diffraction (XRD) pattern of the synthesized powder showed no reflections. The electron micrograph showed an agglomerated particle distribution with an average hydrodynamic particle size of 450 nm. Nanocomposite bioactive glass – nanoclay was prepared by physical mixing, which were then coated onto titanium substrates by electrophoretic deposition. The coatings were characterized for their morphology. The XRD pattern confirmed the presence of nanoclay in the coating. The scanning electron microscopy (SEM) images showed a densification of the coatings as the concentration of nanoclay was increased in the nanocomposites. The corrosion resistance of the nanocomposite coatings was studied in simulated body fluid. The charge transfer resistance increased from 9 × 103 Ω for uncoated substrates to 2.8 × 105 Ω for nanocomposite coatings. Potentiometric polarization studies also showed a similar trend, showing consistency in the electrochemical analysis.
       
  • Impact of field conditions on the strength development of a geopolymer
           stabilized marine clay
    • Abstract: Publication date: Available online 13 October 2018Source: Applied Clay ScienceAuthor(s): Mohammadjavad Yaghoubi, Arul Arulrajah, Mahdi Miri Disfani, Suksun Horpibulsuk, Stephen Darmawan, James Wang A soft marine clay was stabilized with fly-ash (FA) and slag (S) based geopolymers. FA and S with combined contents of 10, 20 and 30% were added to the soft clay and activated with a liquid alkaline activator (L) at various contents. The clay was a marine clay which was dominated by quartz, illite and feldspar. The effect of a number of preparation and curing factors including water content and temperature variation, wetting-drying cycles and mixing time and method were evaluated. The objective of this research was to evaluate the effect of these factors that are likely to occur in ground improvement applications, such as deep soil mixing, on the unconfined compressive strength (UCS), microstructure and mineralogy of the mixtures. Results showed that increasing the FA + S content increased the UCS values significantly through the geopolymerization process, which was evident when increasing the FA + S content from 10% to 20%. Moreover, higher UCS values were achieved when the curing temperature was increased and the strength development was accelerated as a result of accelerated precipitation of FA and S. Furthermore, strength development was enhanced when the L/(FA + S) ratio was increased from 0.75 to 1.0, followed by a decrease at L/(FA + S) ratio of 1.25. Similar trends of strength development were observed by varying the water contents of 0.75, 1.0 and 1.25 liquid limit (LL) of the soil. The increased amount of liquid, L and water, caused less favorable environment, such as lower L molarity and less particle contact, for proper strength development. The UCS values decreased for up to 6 cycles of wetting and drying, where the geopolymeric network was not sufficiently stable, and remained almost constant afterwards. Increasing the mixing time caused more dissolution of FA and S, which resulted in enhancement of the UCS values. Adding FA + S and L to the soil separately resulted in higher UCS values compared to when FA + S and L were mixed together initially and then added to the soil. The microstructure and mineralogy analyses indicated that increasing the curing temperature, as well as the L/(FA + S) ratio resulted in more dissolution of FA and S and formation of calcium sodium aluminum silicate hydrate (CNASH) products.
       
  • Study on corrosion behavior of low carbon steel under different water
           conditions in bentonite of China-Mock-Up
    • Abstract: Publication date: Available online 12 October 2018Source: Applied Clay ScienceAuthor(s): Xin Wei, Yuemiao Liu, Junhua Dong, Shengfei Cao, Jingli Xie, Nan Chen, Fang Xue, Changgang Wang, Wei Ke In China-Mock-Up, the transition of water conditions in bentonite and its influence on the corrosion behavior of four low carbon steel electrochemical sensors buried in bentonite along horizontal direction were investigated by in situ electrochemical impedance spectroscopy (EIS) with the infiltration of groundwater from outside to inside. The results show that in the initial stage of EIS measurement, water in bentonite around the electrochemical sensors from outside to inside is hygroscopic water and chemical bonding water successively. With increasing time, water in the outer bentonite transforms from hygroscopic water to free water. Meanwhile, water in the inner bentonite transforms from chemical bonding water to hygroscopic water. As water in bentonite exists as the chemical bonding water, the equivalent circuit can be described as a pure capacitor, which does not cause the corrosion of low carbon steel. When water in bentonite exists as hygroscopic water, it can be described as a circuit consisting of two leakage capacitors in series, which causes the slight corrosion of the steel. While, in the presence of free water, the equivalent circuit can be described as a free water resistance and two leakage capacitors in series, which causes the serious corrosion of the steel.
       
  • Photocatalytic degradation of trimethoprim on doped Ti-pillared
           montmorillonite
    • Abstract: Publication date: Available online 12 October 2018Source: Applied Clay ScienceAuthor(s): Beatriz González, Raquel Trujillano, Miguel A. Vicente, Vicente Rives, Sophia A. Korili, Antonio Gil Montmorillonite pillared with titanium and doped with Cr3+ or Fe3+ has been tested for the photo-degradation of the antibiotic trimethoprim (trimethoxybenzyl-2,4-pyrimidinediamine) under different conditions, namely, in the dark or in UV light, with or without catalyst, finding excellent catalytic performance under photocatalytic conditions. The degradation by-products were preliminary analysed by mass spectrometry. The results suggested that the molecule broke in two halves, corresponding to its two existing rings. The process continued with the breakage of new fragments from the trimethoxybenzene half, these fragments later reacted with the methoxy groups in this part of the molecule, giving species with m/z values higher than that for the starting molecule, and with the breakage of new fragments.
       
  • Adsorption of reactive red 136 onto chitosan/montmorillonite intercalated
           composite from aqueous solution
    • Abstract: Publication date: Available online 10 October 2018Source: Applied Clay ScienceAuthor(s): Jin Li, Jun Cai, Lian Zhong, Huali Cheng, Han Wang, Qimin Ma Chitosan/montmorillonite intercalated composite (CTS/MMT) was used as an effective adsorbent for removal of reactive red 136 (RR136). Taguchi method attached grey relational analysis was applied to determine the optimal adsorption conditions, including pH, initial concentration of dye, temperature, adsorbent dosage and contact time, for achieving simultaneous maximization of removal percentage and adsorption capacity. The percentage contribution of each adsorption condition was determined in the analysis of variance and shown that the most effective parameter is initial concentration of dye. The optimal adsorption conditions were found in pH 3, initial concentration of dye 240 mg/L, temperature 20 °C, adsorbent dosage 0.4 g/L and contact time 135 min. Under the optimal condition, the removal percentages and adsorption capacity were 74.7% and 445.38 mg/g, respectively. The adsorption behaviors showed that the adsorption isotherms and kinetics were in best agreement with the Toth isotherm and Brouers-Weron-Sotolongo model, respectively. Applicability of mechanistic models exhibited that film diffusion and intra-particle diffusion were involved in the current adsorption processes and intra-particle diffusion was not the only rate-controlling step. CTS/MMT before and after adsorption were characterized through FT-IR, XRD and SEM. The results indicated that the RR136 adsorption process was not only surface adsorption but intercalation, and OH, CONH2, NH2 and SiO group of CTS/MMT were involved in the adsorption process. Moreover, the desorption and regeneration experiments revealed CTS/MMT showed excellent adsorption performance even after 15 adsorption-desorption cycles.
       
  • Kinetic re-evaluation on “Comparative adsorption of Pb(II), Cu(II) and
           Cd(II) on chitosan saturated montmorillonite: Kinetic, thermodynamic and
           equilibrium studies”
    • Abstract: Publication date: Available online 7 May 2018Source: Applied Clay ScienceAuthor(s): Yong-Son Hong
       
 
 
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