Effect of initial pH value on the removal of reactive black dye from water by electrocoagulation (EC) method

Abstract

This study investigates the influence of the initial pH on the removal of reactive black 5 dye (RB5) from water using electrocoagulation (EC) reactor supplied with aluminium electrodes. The influence of the initial pH has been investigated by commencing several sets of continuous flow experiments at five different initial pH values (4, 5, 6, 7, and 8) keeping the current density, inter-electrodes distance, and the concentration of RB5 constant at 2 mA/cm², 4 mm, and 25 mg/L, respectively. The obtained results showed that the removal efficiency increased gradually as the initial pH increased from 4 to 6 to reach its maximum level (96%) at the neutral range of pH, then it decreased to 74% as the initial pH increased to 8. This change of the removal efficiency with the initial pH could be attributed to the predominant species of aluminium coagulants, where in alkaline and acidic conditions; the prevailing species have low adsorption capacity for pollutants. While, in the neutral range of pH, the predominant species have high adsorption capacity for pollutants.