Electrochemical peroxidation as a tool to remove arsenic and copper from smelter wastewater

Electrochemical peroxidation (ECP) is a method that recently has been applied in the treatment of heavy metal polluted wastewater. This method is based on the anodic dissolution of iron to ferrous ions that reacts with H2O2 to produce tiny particles of ferric oxides. These oxides adsorb metals efficiently from aqueous solutions. In the present study, the technique was tested experimentally on copper smelter wastewaters with high concentrations of copper and arsenic. A completely mixed airlift batch reactor was used, and the copper and arsenic removal was measured both for synthetic and real wastewater samples. The concentric iron electrodes acted as ferrous ion source when applying a constant direct current with current reversal every minute and the H2O2 was added dropwise. Initial pH was fixed at 3.5, 5.0 and 6.5, respectively. The best results with the synthetic wastewater showed [99% removal of copper and 80% removal of arsenic (at pH 6.5). When treating the real wastewater samples, both arsenic and copper could be removed more than 99% for all pH levels studied. It can be concluded that presence of other substances in the real wastewater favours the arsenic adsorption and/or precipitation. The copper and arsenic removal velocity was found to be dependent of pH—with the fastest removal at pH 3.5. The ECP could be regarded as a promising remediation method for treating highly contaminated wastewaters since arsenic (from 1000 mg L-1) and copper (from 300 mg L-1) was removed nearly completely from copper smelter wastewaters.