GC–MS identification of DR31 textile dye degradation products during its efficient electrochemical removal from wastewater media

Abstract

DR31 dye is widely used in cotton, silk, polyamide fiber, cellulose fiber, and viscose/silk blended fabric dyeing. Electrochemical oxidation with graphite electrodes was used to successfully degrade Direct Red 31 (DR31) textile dye in its synthetic and actual industrial effluents samples, degradation is confirmed by cyclic voltammetry. The change in concentration of the dyes was followed by UV–Visible spectroscopy and the acquired degradation products were confirmed by GC–MS analysis. Under optimal conditions (dye conc. = 200 mg/L, pH = 2, 300 mg NaCl, and current intensity = 50 mA), the dye was decolorized and degraded with a percent of 98.17 % in 10 min. GC–MS analysis was applied to determine the degradation products, where the large dye molecule is broken down into different products of smaller size. On the other hand, cyclic voltammetry measurements under optimum conditions confirmed the successful degradation of DR31 dye, and are in good agreement with the electrochemical oxidation results. A hypothesized mechanism for DR31 degradation by electrochemical oxidation/reduction using graphite electrodes is depicted.