Electrooxidation of Brown-Colored Molasses Wastewater. Effect of the Electrolyte Salt on the Process Efficiency

In this work, synthetic melanoidin wastes have been treated with conductive-diamond electrochemical oxidation in a bench-scale plant. The results show a significant influence of the current density and also of the electrolyte salts on the efficiency of the treatment. The electrochemical oxidation of the melanoidins in the presence of carbonate or perchlorate does not lead to the complete mineralization of the organics, but to the accumulation of refractory compounds. Conversely, the oxidation of these synthetic wastes in the presence of chlorine, sulfates, or phosphates yields the complete removal of the chemical oxygen demand and total organic carbon of the wastes. In addition, the efficiency (amount of melanoidin removed per Ah) also depends on the electrolyte salt. Thus, the presence of chloride and phosphate anions allows better results to be obtained. These observations have been explained taking into account the important role of the mediated oxidation carried out by the oxidizing electrogenerated agents (peroxodisulfate, peroxodiphosphate, hypochlorite,...) from the oxidation of the electrolyte salts. The results obtained as a function of the current density also confirm the important role of electrogenerated oxidants on the treatment efficiency.