Optimization of Direct Blue 71 (DB71) Removal in UV/H2O2 Process, Using Response Surface Methodology

Abstract Dye compounds are discharged into environment through wastewater produced during various industrial operations and procedures of production and consumption. Given their carcinogenic characteristics, dyes are threats to the environment. Oxidation by hydrogen peroxide and ultraviolet radiation (UV/H2O2) has been reported in various studies for degradation of dyes. In this study, we aimed to optimize direct blue 71 (DB71) removal by UV/H2O2 process, using response surface methodology. Based on an experimental study, performed by D-optimal method, effects of independent variables including pH, hydrogen peroxide concentration, and exposure time on dye removal efficiency were studied (a total of 25 treatments). Optimization of conditions and the analysis of the proposed model were performed using response surface methodology and ANOVA test, respectively. The proposed model for dye removal was statistically significant at a confidence level of 95%. Poor model fit was insignificant at a confidence level of 95%. Dye removal efficiency was dependent on H2O2 concentration and radiation time. The process was not pH-dependent and removal efficiency of DB71 at optimal conditions (220 mg/L hydrogen peroxide and irradiation time of 16 min) was 99.2%. Photochemical oxidation with hydrogen peroxide is an effective method for the removal of DB71 from aqueous solutions. Experimental design with D-optimal method can be used to optimize the process, reduce the number of experimental tests, and provide the best conditions for dye removal.