Nickel foam as a new material for chlortetracycline electrochemical oxidation: Biodegradability improvement and biological treatment

Chlortetracycline CTC is an organochlorine compound released from industrial pharmaceutical waste. This pollutant had dangerous effects in aquatic organisms and human health, since it is responsible for inhibition of microbial activity and growth. In this study, the elimination of CTC from water is targeted. Biodegradability, based on the BOD5/COD ratio was studied, showing the non-feasibility of a direct biological treatment. Cyclic voltammetry analysis on a nickel electrode revealed a significant electrochemical activity of CTC. An electrochemical pre-treatment was therefore carried out ina percolation cell using a nickel foam as a working electrode at the potential of 0.5 V/SCE. The operating parameters were optimized. A degradation yield of 99% was achieved for an initial concentration of pollutant of 50 mg L-1 and a flow rate of 5 mL min(-1) in alkaline conditions. After electrolysis, a total dechlorination of CTC was observed. The biodegradability ratio was improved, from 0.13 to 0.33 after electrolysis; while the dissolved organic carbon (DOC) analysis revealed that the level of mineralization remained low 27%. A 21 days biological treatment with activated sludge was then carried out, leading to an overall mineralization yield of 78%.