Enzyme-electrolytic degradation of dichloromethane: Efficiency, kinetics and mechanism

Enzymatic electrolysis cell (EEC) has advantages over microbial electrolysis cell (MEC) due to the needless of microbe inoculation and high-efficiency of enzymatic reaction. In this study, an EEC was first applied to achieve the effective degradation of halogenated organic pollutants and dichloromethane (CH₂Cl₂) was utilized as a model pollutant. The results indicate that the degradation efficiency of CH₂Cl₂ after 2 hr reaction in the EEC was almost 100%, which was significantly higher than that with enzyme (51.1%) or current (19.0%). The current induced the continuous regeneration of reduced glutathione (GSH), thus CH₂Cl₂ was degraded under the catalysis of GSH-dependent dehalogenase through stepwise dechlorination, and successively formed monochloromethane (CH₃Cl) and methane (CH₄). The kinetic result shows that with a current of 15 mA, the maximum specific degradation rate of CH₂Cl₂ (3.77 × 10^-3hr^-1) was increased by 5.7 times. The optimum condition for CH₂Cl₂ dechlorination was also obtained with pH, current and temperature of 7.0, 15 mA and 35°C, respectively. Importantly, this study helps to understand the behavior of enzymes and the fate of halogenated organic pollutants with EEC, providing a possible treatment technology for halogenated organic pollutants.