Background: Conserving water for human survival and providing future security are important issues that need to be addressed. Methods: In this study, a zeolite modified with hexadecyl trimethyl ammonium bromide (HDTMA-Br), a cationic surfactant, and its application in removing direct blue 129 (DB129) was examined. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize both modified and unmodified zeolites. The effects of operational parameters such as the amount of adsorbent, initial dye concentration and pH on the removal efficiency of the dye were examined. Results: The results showed that in the initial dye concentration of 50 mg/L, the optimum amounts of adsorbent and pH were 0. 3 g and 7, respectively. Increasing the dye concentration from 20 to 100 mg/L resulted in the reduction of the removal efficiency from 100% to 79% in the contact time of 90 minutes. The results indicated the highest attracting correlation with Langmuir model. The maximum adsorbent capacity obtained from Langmuir model was 25 mg/g. The kinetics of the dye adsorption on the modified zeolite followed pseudo-second-order kinetics model. Calculated thermodynamic parameters showed that Gibbs free energy changes (DGo) at temperatures of 20 and 45° C were-29. 41 and-35. 20 kJ/mol, respectively. Enthalpy (DHo) and entropy changes were equal to 41. 181 kJ/mol and 0. 241 J/mol K, respectively. The results showed that the processing was a spontaneous endothermic reaction. The process modeled by artificial neural networks (ANN) showed that the experimental results can be accurately modeled using neural network model. The correlation coefficient found between the experimental and the model results was 0. 951. Conclusion: Due to the low cost, high abundance and availability of zeolite, the removal efficiency of this adsorbent can be increased to desirable levels by modifying.

Introduction: High volumes of wastewater along with contaminants, such as colloids and dyes are discharged from different industries into the environment. These wastewaters create major problems and serious threats for water resources. Therefore, it is essential to treat such wastewaters and reach the effluent discharge standards. In this regard, chitosan as a coagulant has a comparable performance with other coagulants. Moreover, the addition of chitosan and removal of turbidity probably lead to higher efficiency of nanoparticles in lower dosages which is investigated in the current study. Therefore, the purpose of this study was to investigate the efficiency of chitosan and magnesium oxide (MgO) nanoparticles for the removal of color and turbidity. Materials & Methods: Synthetic wastewater was prepared by mixing specific amounts of bentonite and direct blue 71 dye in distilled water. After the preparation of different concentrations of color and turbidity, the experiments were conducted with different dosages of chitosan and MgO separately and in combination. The influence of variables such as pH, initial concentration of dye and turbidity, MgO and chitosan dosages on removal efficiency was investigated in this study. Fidings: According to the results, the highest rate of color and turbidity removal was obtained at 1. 5 mg/L chitosan in combination with 1. 5 g/L MgO with the efficiency of 97. 5%. In addition, the highest removal efficiency was obtained at pH of 7. Discussion & Conclusions: Due to the need for high doses of MgO in high turbidities, the use of chitosan as a coagulant can be effective in reducing the use of MgO.

Present work investigates the capability of oxidative treatment process in the presence of nano silver doped on silicate particles for decolorization of a widely used azo dye, C. I. Direct Blue 129 (DB129) in water samples. Solutions with initial concentration of 20 mgL-1 of dye, within the range of generic concentration in textile wastewaters, were treated under ambient conditions of initial pH of 6. 7 and temperature of 25º c. The operational parameters evaluation including dye and peroxydisulfate concentration, initial pH, nanoparticles dosage and reaction time was studied in an endeavor to reach the higher dye removal efficiency. Subsequently, a removal more than 90% of dye was attained by applying the optimal operational conditions as follow: 0. 4 g of catalyst, 20 mgL-1 of dye, 5 mM of peroxydisulfate and initial pH of 6. 7 in 35 min. Moreover, kinetic study for various parameters in several conditions for treatment process was investigated. Pseudo-first-order reaction rate constants were calculated for the systems. The morphology and crystal structure of Ag-SiO2 nanoparticles were characterized by means of Transmission Electron Microscope (TEM).

Background and purpose: Textile dye effluents have some potential risks which require effective treatment before discharging into the environment. Advanced oxidation processes can remove pollutants faster than other processes due to active hydroxyl radical production; therefore, increase the efficiency of dye removal. This study was aimed at investigating dye removal process using UVA/ZnO and UVA/TiO2 nanocatalysts.Materials and methods: This study was done in a batch reactor on synthetic and real samples and the effects of initial dye concentrations, TiO2 and ZnO nanoparticles dosage, time, pH and interference compounds on efficiency of dye removal was investigated. The Daphnia Magna was used for bioassay test.Results: The removal rates of dye in optimum conditions were 69% and 95.5% by UVA/ZnO and UVA/TiO2 processes, respectively and the optimum pH in the process was 9 and 2, respectively. In this study, the initial concentration of dye and COD were found to have adverse relation with removal rate of dye in two processes (p<0.05, r2 ZnO=0.99, r2 TiO2=0.94). With increasing the catalyst and exposure time at both processes the dye removal rate increased. In this study, LC50 96 h decreased from 96.7 to 44.7 mg/l.Conclusion: The current study showed that TiO2/UVA process with effective optimization of operational factors, has high performance in R.B 86 dye decolorization and reducing toxicity.