Optimal degradation of dye wastewater by ultrasound/Fenton method in the presence of nanoscale iron

An advanced ultrasound/Fenton/nanoscale iron oxidation process was applied for treatment of dye wastewater. In this study, the Taguchi statistical method was used to design experiments for the optimization of the ultrasound/Fenton/nanoscale iron process. The experimental design consisted of testing five factors (dosage of H₂O₂, concentration of Fe^2 +, amount of nanoscale iron added, treatment time, and initial pH), with four levels of each factor tested. Chemical oxygen demand (COD) measurements were conducted to determine the efficiency of the water samples. An analysis of the mean sign-to-noise (S/N) ratio indicated that the optimum combination of levels of the factors providing maximal COD reduction of aqueous azo dyes (500 mg/L) were: treatment time = 60 min, dosage of nanoscale iron = 1 g/L, initial pH = 2, and ratio of [dye]:[H₂O₂]:[Fe^2 +]=1:3.6:2.4. The efficiencies of decolorization and COD reduction were accomplished under these optimum conditions at levels of 99.91% and 63.36%, respectively. The percentage contribution of each factor was determined by the analysis of variance (ANOVA). The results show that the contributions of the five factors—dosage of H₂O₂, concentration of Fe^2 +, amount of nanoscale iron added, treatment time, and initial pH—were 29.33%, 21.37%, 22.51%, 12.93% and 12.35%, respectively.