Abstract: This paper investigates the impact of annealing temperature on the photocatalytic degradation efficiency of rhodamine B (rhB) using a montmorillonite/zinc-oxide (MMT/ZnO) nanocomposite. The MMT/ZnO nanocomposites, synthesized through a chemical method, are annealed for one hour at 300°C, 500°C, and 700°C. The study involves a comprehensive analysis of sample composition, surface morphology, and structure using various analytical methods, including Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Fourier Transform Infrared Spectroscopy (FTIR). RhB degradation efficiency is assessed by monitoring changes in dye concentration in the solution after exposure to UVC radiation, measured with UV-Vis spectroscopy. By-products resulting from the photocatalysis process are identified through LCMS analysis. The results demonstrate that MMT/ZnO annealed at 500°C (referred to as MZ@500) exhibits the highest capability for rhB decomposition, achieving a remarkable 95.5% degradation efficiency with 10 ppm of rhB and 0.1 g/L of MZ@500. Furthermore, this composite effectively fragments the dye's chromophore structure into smaller, ring-broken compounds.
Abstract: Phenols and their derivatives are aromatic compounds containing hydroxyl or sulfonic groups attached to a benzene ring structure. Even in low concentrations, phenols are hazardous pollutants posing a threat to living organisms. This study aims to explore the removal of phenol utilizing nano clay modified with hexadecyltrimethylammonium (HDTAM) cations. The research was conducted in three phases. The first phase involved batch experiments to eliminate phenol from aqueous solutions. In the second phase, the modified nano clay was applied in a continuous system for practical purposes, investigating the impact of varying clay concentration and weight in the adsorption column. The third phase focused on studying the performance of columns in series. Results from the initial phase indicated equilibrium between the solution and adsorbent after approximately 1 hour, a significant reduction compared to unmodified nano clay. Increasing the initial concentration of phenol from 50 to 800 milligrams per liter led to enhanced adsorption capacity but decreased removal efficiency from 70% to 45%. Kinetic studies revealed a pseudo-second-order adsorption process, while isotherm studies indicated adherence to both Langmuir and Freundlich models, with greater conformity to the Freundlich isotherm. The adsorption-separation model derived from experiments suggested surface adsorption as the primary process at low concentrations, transitioning to dominant separation with increasing concentration. The second phase demonstrated the effective performance of modified clay in continuous processes, with higher flow rates resulting in reduced efficiency and adsorption capacity of phenol. Utilizing the modified clay in the adsorption column increased phenol adsorption capacity and efficiency from 14.5% to 27%. Finally, employing two columns in series in the third phase boosted adsorption capacity from 37% to 50%.
Abstract: Landfill siting is a major problem in solid waste management. Many aspects should be considered when selecting an appropriate site for a landfill in any particular region. In the current research, seventeen criteria were considered, including rivers, water bodies (lakes), geology, slope, elevation, power lines, groundwater depth, major district roads, archaeological sites, urban centers, infrastructure, villages, pipelines, quarrying, forests, aspect (wind), and agricultural areas. Several random open dump waste disposal sites are dispersed throughout the Ranya District. This research employed the integration of a Geographic Information System (GIS) and Analytical Hierarchy Process (AHP) to identify the optimal sites for the establishment of sanitary landfills. The seventeen criteria were mapped and assigned sub-criteria within GIS software. Subsequently, the normalized weights from the AHP were identified for each measure to generate the final Land Suitability Index (LSI) map for the site. Consequently, approximately 0.34% of the entire study area, equivalent to roughly 2,396,000 square meters, is estimated to be suitable for locating a landfill. Additionally, the suitable sites were categorized into moderately suitable, suitable, and mostly suitable sites. The normalized weight analysis revealed that groundwater depth significantly influences the selection of the best landfill site.
Abstract: The study aimed to assess the effects of ultrasound-assisted thermal pre-treatment on biogas production by co-digesting stress-adapted microalgae (Synechocystis sp.) with a combination of mixed municipal and industrial sewage sludge under anaerobic conditions. The pre-treatment process involved subjecting the microalgae biomass to thermal pre-treatment at temperatures of 70, 90, and 110 oC, while utilizing ultrasound pre-treatment for the sludge (with an average solids content of 16.7 g.L-1) at a frequency of 25 kHz and power output of 400 W for durations of 3, 9, and 15 minutes before the main digestion process. The experiment was designed by response surface methodology with a central composite design. The results revealed that the model exhibited statistical significance, with a probability value (Prob > F) of less than 0.05. Pre-treated samples demonstrated a substantial increase in biogas production compared to untreated samples, showing an average 1.4 to 5.6-fold enhancement. Optimization analysis indicated that the highest cumulative biogas production, amounting to 706 NmL, could be achieved after 2 weeks by pre-heating the microalgae cells at 110 oC for 1 hour and subjecting the sewage sludge to ultrasound pre-treatment for 3 minutes. These findings highlight the potential of ultrasound-assisted thermal pre-treatment technology as a strategy to enhance biogas production through the co-digestion of stress-resilient microalgae and sewage sludge.
Abstract: Because heavy metals can build up within the bodies of living things, and because of chemical reactions, they can become poisonous and carcinogenic. Among other things, heavy metal-containing salts are one way these elements enter the body. In Khuzestan Province, Iran, the Shorbarik River is one of the most significant rivers from which salt is mined. In order to assess the health and quality of the salt taken from the Shorbarik River in accordance with national regulations, this study looked into the concentration of heavy metals (lead and cadmium) in these salts. The Shorbarik River was the study region, and the surface salts of the dried bed were sampled in four stages. After drying in an oven, they were injected with acid into an atomic absorption device. Due to the high concentration of cadmium in the region's salts, the risk of cancer from exposure to heavy metals through salt consumption is serious. Ecologically, the Shorbarik River's salt is generally low in lead contamination and considerably high in cadmium contamination, with high levels in the spring and summer. Therefore, it is recommended to consume refined salt.
Abstract: Industries extensively use synthetic dyes, and it is crucial to eliminate them from effluents to prevent their accumulation in nature. The elimination of synthetic dyes is effectively achieved through the well-established method of adsorption, and previous researchers have developed a range of materials dedicated to the adsorption of such dyes. In this regard, natural materials have received a lot of attention as environmentally friendly. This study examined the ability of SiO2-based stone samples, including silica, zeolite, pumice, and scoria, to adsorb carmoisine and malachite green dyes from water. The ball-milling method was utilized to prepare the nanosized adsorbents. Physicochemical properties were evaluated by analytical methods, including DLS, XRD, XRF, BET, and FTIR. The removal of dyes was experimentally undertaken utilizing both granular and nanosized adsorbents with conditions of 30°C temperature, pH 7, and initial dye concentrations set at 45 mg l-1. Adsorption isotherm models and kinetic models were evaluated for dye adsorption. The highest level of adsorption capacities for carmoisine and malachite green were 54.42 and 19.01 mg g-1, respectively. The findings of this research demonstrated that nano-sized scoria and silica have the potential to be used as efficient adsorbents in cationic and anionic dyes removal, respectively.
Abstract: An airlift reactor with the external loop (EXL ALFR) is a widely used modified version of a Bubble Column Reactor (BCR). An EXL ALFR can also be used for a three-phase system with the solid phase in a packed or fluidized form. An EXL ALFR provides design flexibility for conventional chemical reactions as well as biological reactions. Shear is an important factor for the reactors handling immobilized enzymes. In the current investigation, the effect of the design variables, like gas hold-up, the velocity of circulating liquid, and the distribution of bubble dimension, was compared for an EXL ALFR and an external loop airlift reactor with a packed bed (EXL ALFR-PB). Particle Image Velocimetry (PIV) was employed for the liquid axial velocity in the downcomer of the reactors, and the computational fluid dynamic with the Population Balance Model (CFD-PBM) was employed. The minimum percentage of errors of 2.3% and 1.2% and the maximum of 4.2% and 3.4% were obtained for the experimental and predicted values of gas hold-up in the EXL ALFR and EXL ALFR-PB, respectively. For the velocity of the circulating liquid, the predicted and experimental values of their minimum percentage error were 1.1% and 0.5% and a maximum of 4.3% and 4.5% in EXL ALFR and EXL ALFR-PB, respectively. Also, the pressure drops calculated from the Ergun equation and CFD simulation had a 0 to 4% difference, indicating good agreement.
Abstract: Coprinus cinereus (NBRC 30628) peroxidase was implemented to eliminate the diazo dye of reactive black 5 (RB5). The optimization was conducted in batch mode using three approaches, i.e., the one-factor-at-a-time (OFAT), factorial design, and response surface methodology (RSM). Based on the results of the OFAT method, the optimum conditions for decolorization of RB5 dye were at a temperature of 30oC, a pH of 9-10, an H2O2 concentration of 3.9 mM, and an RB5 concentration of 40 mg/L. In the first stage of statistical optimization, these factors plus enzyme activity were screened by the 2-factorial design, wherein enzyme activity, temperature, and hydrogen peroxide concentration were distinguished as the most significant parameters in the enzymatic decolorization of RB5.In the second stage, RSM was applied over three adopted factors through the central composite design (CCD), and a reduced cubic polynomial model was generated, which indicated an accurate regression (R2 = 0.997, Adj.R2 = 0.994) and no significant lack of fit (p-value> 0.05). The contour and surface plots suggested that the removal efficiency was enhanced by increased enzyme activity and decreased H2O2 concentration and temperature. The optimum condition was obtained at 1.0 mM H2O2, 6 U/mL enzyme activity, and 35oC for a maximum decolorization efficiency of 96.046%.
Abstract: The present study evaluated the impact of the concentration of a microbial enzyme complex on the aerobic purification rate of domestic wastewater. A diverse and active microbial enzyme complex allows the efficient degradation of organic pollutants present in wastewater. In addition, environmental conditions, such as nutrient availability and optimum temperature, favor enzymatic activity and the performance of the purification process. For this purpose, aerobic depuration tests were carried out in a bioreactor considering three concentration levels of the microbial enzyme complex (1.0, 1.5 and 2.0 g/L), controlled temperature of 17 °C and dissolved oxygen concentration of 3.0 ppm. The adaptation process of the microorganisms lasted two days, with a daily decrease in the Chemical Oxygen Demand (COD) of 62.8; 71.1 and 77.9 ppm, respectively. Therefore, the removal rate increased with the concentration of the microbial enzyme complex and the treatment time had a significant effect on the speed of purification.
Abstract: Removal of recalcitrant dyes from agroindustrial wastewater production in flower processes represents a significant environmental challenge for flower industries worldwide. Advanced oxidation processes (AOPs) emerge as a clean and effective costly alternative for removing dye contaminants in wastewater. We use an electro-Fenton technique as an alternative for the treatment of colored wastewater from flower-producing crops in Colombia. Initially, physicochemical characterization of the wastewater was carried out by Chemical Oxygen Demand (COD), color, pH, conductivity, temperature, and oxidation-reduction potential. Subsequently, an electrochemical process was carried out through a power source and six iron electrodes. Variables such as hydrogen peroxide concentration (500 and 700 mg/l H2O2), amperage (1 and 2 A), and treatment time (60 and 90 minutes) were controlled. Based on a desirability function for multiple response analysis, the electro-Fenton process allowed a maximum COD removal of 80.9% and 88.5% for color (desirability criterion of 86%). Residence time in the reactor, voltage, current density, and concentration of hydrogen peroxide were the most significant variables. Finally, we explain the role of other physicochemical variables involved during the dye degradation process.
Abstract: Suspended sediment load is an indicator of erosion in watersheds. Therefore, accurately estimating the daily suspended sediment load (DSSL) is an important issue in river engineering. In this research, Artificial Neural Networks (ANN), Genetic Expression Programming (GEP) intelligent models, and the traditional Sediment rating curve (SRC) model were used to estimate DSSL in the Kasilian and Rood Zard watersheds in Iran. The input data to the models included instantaneous flow discharge (Q), average daily flow discharge (Qi), average daily flow discharge with a delay of three days (Qi-1,Qi-2,Qi-3), average daily precipitation (Pi), and average daily precipitation with a delay of three days (Pi-1,Pi-2,Pi-3); the output data was DSSL. In this research, the self-organizing map (SOM) artificial neural network was used for data clustering, and gamma test (GT) methods were used to obtain the best combination of input variables to intelligent models. The results showed that the best models for estimating DSSL in the Kasilian and Rood Zard watersheds were respectively the ANN model with an activation function of tangent sigmoid with the best combination of input variables (Qi-1,Qi-2,Qi-3,Pi,Pi-1,Pi-2,Pi-3) and the GEP model with the input variables Qi,Qi-1,Qi-2,Pi,Pi-1,Pi-2,Pi-3. The statistical values of the ANN-tangent sigmoid model for the Kasilian watershed were MAE=231.4 (ton day-1), RMSE=578.6 (ton day-1), NSE =0.98, and R2=0.98; these values for the GEP model in the Rood Zard watershed were MAE=475.7 (ton day-1), RMSE=1671.9 (ton day-1), NSE=0.99, and R2=0.99. The SRC model in the Kasilian watershed with R2=0.34 and NSE=0.08 and the Rood Zard watershed with R2=0.59 and NSE=-0.11 showed the low accuracy of this model in estimating DSSL.
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