The influence of cathodic materials and optimization of the removal of the chromium (VI) from tannery wastewater by electrocoagulation

Abstract

The present work focuses on the optimization of the removal percentage of Chromium (VI) from a real tannery effluent by electrocoagulation process (EC). The influence of high efficiency cathodic materials (titanium and nickel) was also investigated in this work. The tannery effluent is from the town of Maroua in the Far North Region in Cameroon. The effectiveness of the main operational parameters such as current intensity, initial Cr (VI) concentration, initial pH as well as solution conductivity was examined. All experiments were carried out in an electrocoagulation cell with an effective volume of 400 mL using two electrode combinations as anode/cathode (Al/Ti and Al/Ni). It was found that the Al/Ti combination exhibits higher removal efficiency than Al/Ni under the same operational conditions. Cr (VI) removal efficiencies of 90.93 % and 84.30 % were respectively observed for the Al/Ti and Al/Ni electrodes with an optimal initial pH (pH=6). The maximum current intensity, the maximum initial Cr (VI) concentration as well as the NaCl concentration were 0.4 A, 10 mg/L Cr(VI) and 1.5 g/L respectively. Response surface methodology by the mean of central composite design was performed. The influence of current intensity (100–300 mA), electrolysis time (10–30 min) and interelectrode spacing (1–3 cm), the probability and the mathematical model were highly discussed. According to the experimental design results, the removal of Cr (VI) in the real tannery effluent was up to 99.58 %. For the aforementioned efficiency it requires the optimum values of 211.891 mA, 36.8179 min and 1.609 cm for current intensity, time and the interelectrode spacing, respectively. EC has shown to be easy to operate, to be economic by using cheaper electrodes and efficient for the treatment of real tannery effluent.