Removal of Cr3+ by electrocoagulation with multiple electrodes: Bipolar and monopolar configurations

Removal of Cr3+ from aqueous solutions by electrocoagulation (EC) with multiple electrodes was studied with both bipolar and monopolar configurations. The influence of chloride ions, pH, initial Cr3+ concentration and cell current on removal performance was investigated in a batch stirred cell. It was noted that, the enhancement of solubility of Cr(OH)3 and co-precipitated [Cr, Fe](OH)3 in presence of chloride ions results in reduction of removal efficiency. Removal of Cr3+ improved at higher pH due to combined effect of precipitation, co-precipitation as solid solution like species, adsorption, cathodic reduction and sweep coagulation. The maximum Cr3+ removal per unit charge loading was found to be increasing with increase in initial Cr3+ concentration. The cell current efficiency was less than that predicted from Faraday's law of electrolysis for both configurations. The operating cost was estimated from the power cost and cost of electrode material. The former was 40% and the later was 43% higher for bipolar configuration compared to monopolar configuration for achieving final chromium discharge limit of 2.0 mg/l.