In the present study, ultrasonic-assisted Fenton process called sono-Fenton (SF) with low concentration of Fenton reagents was studied via degradation of Direct Blue 71. Influences of seven operational parameters including initial pH (pH 0 ), initial concentration of pollutant (C 0 ), dose of Fenton reagents (C Fe and C H2O2 ), ultrasound irradiation frequency (Fr S ), ultrasound irradiation power (P S ), and treatment time (t SF ) were investigated on the dye removal efficiency (DR). A combined design of experiments consists of full factorial for t SF , and Taguchi for other six parameters was designed, and experiments were conducted in accordance with the design. The experimental data were collected using a batch reactor equipped with controllable ultrasonic bath. The DR of 0-33.5 mg/l was achieved under experimental conditions. These results approved that the SF process can be a promising approach in terms of colored wastewater treatment. The data were used for model building by Taguchi and artificial neural network. Further statistical tests were applied to exhibit models goodness and to compare models. Finally, optimization process was carried out using Taguchi and genetic algorithm. The optimization procedure causes optimal point which gives an insight of optimal operating condition.

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Background: Chromium (VI) is a hazardous pollutant that enters into the environment through different industrial wastewater. Therefore, Choice a suitable method for removal of the pollutant before discharging into the environment is necessary. The aim of this work was performance evaluation of Electro-Fenton process (EFP) in removal of hexavalent chromium in the presence of cyanide, as an interfering agent, from synthetic wastewaters. Methods: In this experimental study, a reactor with 1 L useful volume and 4 electrodes made of iron was used. pH, initial concentration of chromium (VI), voltage, hydrogen peroxide and cyanide concentration, as an interfering agent, were investigated in order to determine the process efficiency. Results: Results reveals that the considered parameters were affected on the efficiency of the process. In optimum condition, pH=3 and voltage=20 V, initial concentration=100 mg/L, concentration of hydrogen peroxide=50 mL/L the maximum efficiency was reached up to 97%. Cyanide Presence, in the same condition, reduced the efficiency under 50 % and also, the efficiency was decreased by changing the parameters level from optimum condition. Conclusion: Results indicate the proper efficiency of chromium (VI) by EFP process; however presence of other pollutants such as cyanide can cause efficiency decrease which must be considered in the process application.