This study investigated the potential of 4A zeolite, named4AZW in this work, generated by natural gas dehydration units as solid waste after several treatment cycles, as a low-cost adsorbent to separately remove two cationic dyes, methylene blue (MB) and malachite green (MG), from an aqueous solution within a batch process. The adsorbent material was characterized by N2gas adsorption–desorption, X-ray fluorescence spectrometry, X-ray diffraction, FT-IR spectroscopy, and the determination of its cation exchange capacity and point of zero charge. The influence of key operating parameters, such as the pH, adsorbent dosage, ionic strength, contact time, initial dye concentration, and temperature, was investigated. Three independent variables acting on MB adsorption performance were selected from the Box–Behnken design (BBD) and for process modeling and optimization. An analysis of variance (ANOVA), an F-test, and p-values were used to analyze the main and interaction effects. The experimental data were satisfyingly fitted with quadratic regression with adjusted R2= 0.9961. The pseudo-second-order kinetic model described the adsorption of the dyes on 4AZW. The equilibrium data were well-fitted by the Langmuir model for each adsorption system (MB-4AZW and MG-4AZW) with maximum adsorption capacity (qmax) values of 9.95 and 45.64 mg/g, respectively, at 25 °C. Thermodynamics studies showed that both adsorption systems are spontaneous and endothermic.
In the present research, zeolite is used for the removal of toxic Congo red dye from water solution. The effects of different operating conditions such as hydrogen potential (pH), contact time (time), zeolite dose (D), initial dye concentration (C0), and ionic strength (I) are investigated for Congo red adsorption under batch mode. It was found that the adsorption process was greatly affected by the initial pH of the dye solution. The removal efficiency decreased from 97.68 to 5.22% when the pH varied from 3 to 5; thus, acidic conditions clearly improve Congo red adsorption on zeolite. At pH 3, an increase in C0 and I and decrease in D resulted in an increase in the adsorption capacity qe. The effects of these three parameters and their interactions were also investigated using the 23 full factorial design experiments approach where qe was chosen as the response. The results obtained from this method followed by the analysis of variance and the Student’s t-test show that, the influence of these parameters on dye adsorption process are in the order I < C0 < D. The kinetic studies revealed that adsorption follows a pseudo-second-order kinetic model. The adsorption isotherms experimental data were analyzed using the Langmuir, Freundlich, and Temkin isotherms models. The Freundlich isotherm was the best-fit model to the experimental data. The fitting of kinetics and isotherm models was evaluated by using non-linear modeling, R2, MSE, and RMSE.
Due to their cost-effectiveness, low toxicity, and naturally renewable properties, bio-coagulants for water treatment are gaining popularity. In this context, four bio-coagulants were tested for their ability in turbidity reduction in a synthetic bentonite suspension: Opuntia ficus indica (OFI) and Moringa oleifera (MO) seeds, two well-established vegetal materials in the domain of bio-coagulation, and Algerian Aloe vera (AV) and Pinus halepensis seeds (PHS), both of which have received very few or no study in turbidity reduction in water and wastewater. A comparative study was conducted with regard to two well-known inorganic coagulants, ferric chloride and Alum. Extraction salts, pH, coagulant dose, initial turbidity, and aging effects were examined. When compared to chemical coagulants, the four bio-coagulants worked very well, removing approximately 100% of the turbidity at natural pH of 7.5 using optimal doses of 1.5, 3, 3, 3.5, 1.5, and 1.5 mL/200 mL for AV, OFI, MO, PHS, Alum, and FeCl3, respectively, at a broad range of pH (2 to 8), and causing no pH alteration of the treated water. Polysaccharides and proteins involved in inter-particle bridging and charge neutralization may be the active coagulation-flocculation molecules. The four bio-coagulants produced less sludge amount than Alum and Ferric chloride. This research not only shows that MO and OFI are effective in eliminating turbidity, but it also highlights the great potential of Algerian AV and PHS seeds as promising bio-coagulants in the treatment of polluted water.
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