Optimization of electro-oxidation process for the treatment of Reactive Orange 107 using response surface methodology

Textile industries release large amount of wastewater to the environment which alters the clarity of water, interfere with light penetration, and pose toxicity to microbes and fish species. In order to remove the dye from wastewater, this study aimed to optimize electro-oxidation process for the degradation of textile dye C.I. Reactive Orange 107 in wastewater using a statistical tool.

The wastewater was synthetically prepared and experiments were designed as the function of variables such as pH (X(1)), NaCl concentration (X(2)), and electrolysis time (X(3)). Graphite electrode was used for all experiments and current was fixed at 34.96 mA cm(-2). The response color and chemical oxygen demand (COD) were measured. UV-visible spectra were recorded at different time intervals and the intermediate was analyzed using FTIR spectrum.

The relevant quadratic and interaction terms of factors were investigated. The coefficient of determination (R(2)) value of 0.8227 and 0.9265 for color and COD removal, respectively, indicate the adequacy of the model. The variables such as X(2) and X(3) are significant for color and X(3) is significant for COD removal.

The electro-oxidation process efficiently removes color and COD from the Reactive Orange 107 contaminated wastewater. The optimum conditions obtained from the statistical analysis at pH 9.4, NaCl concentration of 0.08 M, and electrolysis time of 16.0 min show maximum color and COD removal of 98%, and 90%, respectively. UV-visible spectrum confirms the decoloration and FTIR spectra show the formation of intermediates.