Electrocatalytic dechlorination of 2,4-dichlorophenol in bioelectrochemical systems

In this work, the cathodic electro-dechlorination of 2,4-DCP in a Microbial Fuel Cell (MFC) was studied. To do that, an MFC externally connected with a 120 Omega load was operated by feeding a synthetic wastewater with 300 ppm of 2,4-DCP to the abiotic cathode compartment and sodium acetate to the biotic anode with electroactive bacteria. During the experiments, all the intermediates (2-chlorophenol and 4-chlorophenol) and final products (phenol and Cl-) from the dechlorination of 2,4-DCP were monitored. Results show that the bio-assisted electroreductive treatment achieved a cathodic dechlorination yield of a 57% after 24 h, which increases up to 88% after 72 h. In addition, because of the dechlorination of 2,4-DCP, the biodegradability of the synthetic wastewater, expressed as the ratio BOD/COD, was increased from negative values (corresponding to toxic effluents) up to 0.568. Meanwhile, the toxicity decreased drastically, with EC50 values that increased from 0.021 to 0.228 mmol L-1. Operation current densities during the bioassisted electro-dehalogenation process were significant and decreased from initial values of 0.14 down to 0.04 mA cm(-2). These results indicate that the bioelectrochemical technology can produce small amounts of energy while dechlorinating an extremely hazardous waste.