Using modulated current for energy minimization in the electrochemical treatment of effluents containing organic pollutants.

Anodic oxidation of recalcitrant organic compounds suffers from loss of efficiency as the concentration decreases, leading to high energy consumption. Here, we propose a modulated current (MC) technique to control and maintain the applied current as close as possible to its limiting value throughout the electrolysis, thus ensuring high mineralization current efficiency. The efficacy of this technique was first validated for caffeic acid (CA) electrooxidation using a boron-doped diamond (BDD) anode and was then confirmed for the degradation of a wastewater containing phenolic compounds from wet coffee processing. Combining MC and constant current (CC) operation for CA electrolysis resulted in a substantial reduction of the specific energy consumption from 256 to 52.4 kWh kg-1 TOC, due to improvement of the mineralization current efficiency from 17.9 to 77.1%. The MC+CC technique was also successful in reducing the energy consumption for a real coffee processing wastewater mineralization, demonstrating its suitability as a simple and effective tool that can be used to reduce the energy costs in electrochemical treatment of effluents containing organic pollutants.