Decolourization of Rhodamine B from aqueous solution by electrochemical oxidation using graphite electrodes

This study investigated the colour removal efficiency of Rhodamine B (RhB) by electrochemical oxidation. The influences of various operating variables such as current density (from 5 to 25 mA/cm2), initial concentration of dye solution (from 50 to 250 mg/L), initial pH of solution (3, 5, 7, 9), the stirrer speed (150–300 rpm) and the concentration of electrolytes (0.025–0.10 M NaCl) on removal efficiency were explored in a batch mode treatment to achieve a higher removal capacity. The results obtained with synthetic wastewater revealed that the most effective removal of dye could be achieved when the pH was kept neutral. The results showed that the colour removal increases with the increase in applied current density, NaCl concentration, while it was found to decrease with the increase in initial dye concentration. The complete (100%) colour removal has been achieved under the optimal experimental conditions such as NaCl concentration of 0.05 M, applied current density of 15 mA/cm2, initial pH 7.0, stirrer speed of 200 rpm  and electrolysis time of 40 min. The result of UV–vis spectrum analysis confirms the removal of colour from RhB aqueous solution at the short treatment time. In addition, the increase of current intensity, in the range of 0.6–2.0 A, enhanced the treatment rate. The method was found to be highly efficient and relatively fast compared to conventional treatment techniques.