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Experiments were performed in batch mode of operation using iron electrodes to remove chromium from effluent by electrocoagulation, and the effect of various operating parameters was investigated. The maximum hexavalent chromium removal efficiency of 100% from a synthetic solution containing hexavalent chromium was obtained for an electrolysis time of 15 min at the optimum current density of 50 mA cm−2, interelectrode distance 0.5 cm, and solution pH of 4. The real electroplating industry effluent was characterized using the standard diphenylcarbazide (DPC) method. A 100% chromium removal efficiency was obtained for both trivalent and hexavalent chromium, for an electrolysis time of 45 min at 4 pH. It was found that Cr(VI) is initially reduced to Cr(III) in the acidic medium. An increase in the pH of the effluent was also noticed in the acidic medium due to the generation of hydroxyl ions. Experiments were performed for the removal of chromium using ferric chloride as the coagulant, and it was found that electrocoagulation is more efficient and relatively faster compared to chemical coagulation.
Verma et al. (Thu,) studied this question.