Removal of Disulfine blue from aqueous solutions using Electrofenton process: optimization by Taguchi orthogonal array design

Synthetic dyes are used for coloring many different products such as textiles, paper, cosmetics and drugs [۱]. Disulfine blue is a synthetic dye that has been widely applied in different industries including coloring paper, temporary hair colorant, dyeing cottons, wools and so on. In spite of its applications and advantages, it can cause some illnesses for humans. So, its removal from water resources is still a vital task [۲]. The advanced oxidation processes (AOPs) constitute an attractive approach due to the high oxidation potential of hydroxyl radicals, their non-selective nature and the possibility of rendering full mineralization of a wide variety of organic pollutants. The electrofenton process is the most common AOP processes based on Fenton’s reaction, which enhances the degradation of organic compounds with generated hydroxy radicals. In electrofenton, H۲O۲ is continuously supplied to a contaminated acidic solution by the two-electron reduction of injected O۲ at the cathode, whereas Fe۲+ ion is added to react with this species to generate Fe۳+ ion and •OH in the bulk from Fenton’s reaction, which is mainly propagated by the cathodic reduction of Fe۳+ ion to Fe۲+ ion [۳].The purpose of this work was to study the degradation of Disulfine blue dye by electrofenton process. In the present study, an electrofenton glass reactor (۹۰۰ mL) equipped with two iron electrods (۶۳ × ۸۰ × ۲ mm) and a power supply was constructed for removal of Disulfine blue from polluted waters. The effects of affecting experimental parameters including applied voltage (۵, ۱۰, ۱۵, ۲۰ V), ionic strength (۰, ۰.۰۵, ۰.۱, ۰.۲ M), dye concentration (۵۰, ۱۰۰, ۲۰۰, ۲۵۰ mg L-۱), pH of solution (۲, ۳, ۴, ۶) and percentage of H۲O۲ (۱۰, ۲۰, ۲۵ ,۳۰ %) were investigated using Taguchi orthogonal array design method (OA۱۶). The residual concentration of Disulfine blue after electrofenton process was determined using UV-Vis spectrophotometer at wavelength of ۶۳۹ nm in the time range of ۰-۹۰ min with time intervals of ۱۰ min and dye removal efficiencies were obtained. Based on the results, the optimum conditions were obtained as pH: ۲, voltage: ۲۰ V, H۲O۲:۱۰ %, salt concentration (Na۲SO۴): ۰.۱ M and the initial concentration of dye: ۵۰ mg L-۱. Under the optimum conditions, more than ۹۹ % of Disulfine blue was removed during ۵۰ min.The results confirmed the eclectrofenton process is able to remove Disulfine blue with maximum efficiency at a short period of time.