In the present study, reactive red 198 (RR198) dye removal from aqueous solutions by adsorption using municipal solid waste (MSW) compost ash was investigated in batch mode. SEM, XRF, XRD, and BET/BJH analyses were used to characterize MSW compost ash. CNHS and organic matter content analyses showed a low percentage of carbon and organic matter to be incorporated in MSW compost ash. The design of adsorption experiments was performed by Box–Behnken design (BBD), and process variables were modeled and optimized using Box–Behnken design-response surface methodology (BBD-RSM) and genetic algorithm-artificial neural network (GA-ANN). BBD-RSM approach disclosed that a quadratic polynomial model fitted well to the experimental data (F-value = 94.596 and R2 = 0.9436), and ANN suggested a three-layer model with test-R2 = 0.9832, the structure of 4-8-1, and learning algorithm type of Levenberg–Marquardt backpropagation. The same optimization results were suggested by BBD-RSM and GA-ANN approaches so that the optimum conditions for RR198 absorption was observed at pH = 3, operating time = 80 min, RR198 = 20 mg L−1 and MSW compost ash dosage = 2 g L−1. The adsorption behavior was appropriately described by Freundlich isotherm, pseudo-second-order kinetic model. Further, the data were found to be better described with the nonlinear when compared to the linear form of these equations. Also, the thermodynamic study revealed the spontaneous and exothermic nature of the adsorption process. In relation to the reuse, a 12.1% reduction in the adsorption efficiency was seen after five successive cycles. The present study showed that MSW compost ash as an economical, reusable, and efficient adsorbent would be desirable for application in the adsorption process to dye wastewater treatment, and both BBD-RSM and GA-ANN approaches are highly potential methods in adsorption modeling and optimization study of the adsorption process. The present work also provides preliminary information, which is helpful for developing the adsorption process on an industrial scale.

Background & objectives: Conventional methods are not an efficient method in the removal of resistant organic pollution. Ozone molecules in the presence of anion persulfate can be used as an appropriate method for the removal of these pollutants. The aim of this study is to determine the efficiency of the combined process of ozone and radical sulfate in decomposition of SDBS and reduce the concentration of this pollutant in aqueous. Methods: In this experimental study, use of semi-batch reactor by one liter volume was used semi-continuously. The effect of pH (3-11), concentration of persulfate (10-100 mM/L), concentration of O 3 (1-5 mg/L.hr) and initial concentration of SDBS (10-100 mg/L) were investigated. The kinetics of the reaction, effect of radical scavenger and COD removal in the proper conditions of the process was determined. The concentration of SDBS and COD were measured using a standard reference method. Results: The efficiency of process in 40 minute was more than 97 percent while the process parameters were pH=3, initial concentration of SDBS was 10 mg/L, concentration of O 3 was 5 mg/L.hr and persulfate anions was 20 mM/L. By changing the parameters and the presence of radical scavenger, process efficiency decreased. The efficiency of COD removal in 70 minutes was 80 percent. The reaction kinetic followed by first order kinetic. Conclusion: The ozonation process in the presence of persulfate anion due to the production of active persulfate radical can be suitable method for the removal of POPs such as SDBS. By this method, it is possible to increase the treatment of the wastewater containing this pollutant and reduce the organic loading to environment.

Background and Objectives: Chemical Oxidation Demand (COD) is an important parameter in treatment of leachate. Leachate from solid waste has high pollutants that must be treated before discharge to environment. The aim of this study was optimization of US-Electro/persulfate process, predicate of optimum conditions by RSM for landfill leachate treatment. Methods: In this experimental study, a sonochemical reactor with one liter volume that equipped with 40 KHz and two Iron electrodes as an anode and two Copper electrodes as a cathode that connected to direct current supply source was used. In the final step of study, pH (2-4), S2O8 2-(1-2 g/L), direct electrical current (1.5-3 A) and reaction time parameters as an independent parameters were studied. In optimum condition, corrosion of the electrodes in anode and energy consumption were measured. Sludge properties before and after the process were analyzed by SEM/EDAX and FT-IR spectroscopy. Results: By using this software (design Expert), the optimum condition was done at PH=3.41, S2O8 2-dose=1.2 g/L, current density=2.41 A, and reaction time were 70 min. In this condition the efficiency of COD removal was 75 %. The R-squared and Adj R-squared process was 0.78 and 0.88 respectively. The electrodes corrosion in optimum condition were 0.77 g and energy consumption was 9.23 kW/kg COD. The results of analysis indicate that changes in sludge during the process has happened and elements structure in leachate has observed, the most obvious oxygen and iron increased in sludge after the process. Conclusion:The US-Electro/persulfate has a good efficiency in COD removal and with this model can be tested with a few run and high accuracy to optimize the process.