Electrochemical hydrodechlorination of perchloroethylene in groundwater on a Ni-doped graphene composite cathode driven by a microbial fuel cell

Stepwise dechlorination of chlorinated alkenes on an Fe-Ni/rGO/Ni foam cathode: Product control by one-electron-transfer reactions

Research on the stepwise hydrogenation dechlorination of chlorinated alkenes forms an important basis for eliminating toxic intermediate incomplete dechlorination products. The low-cost Fe-Ni/rGO/Ni foam cathode both supplied electrons and exhibited hydrogen conversion activity, and it was an excellent tool for the study of stepwise dechlorination. Electrochemical reduction experiments were carried out on homologous chlorinated alkenes. The conditions affecting the dechlorination efficiency and the repeatability of the catalytic electrode were analyzed. The trichloroethylene (TCE) removal rates were all above 78.0% over 8 cycles. The maximum EHDC efficiency was as high as 86.1%, and the faradaic efficiency was over 78.8%. Electrochemical methods combined with the calculation of the electron transfer number are proposed to verify the good hydrogenation ability of the electrode and the stepwise reduction ability at proper voltages. The stepwise dechlorination electroreduction characteristics of chlorinated alkenes were explained. The C-Cl bond dissociation enthalpies of chlorinated alkenes were calculated by density functional theory (DFT), and the 4-Cl and 5-Cl of TCE were expected to be removed first. The stepwise cleavage of chlorinated alkenes on Fe-Ni/rGO/Ni foam during dichlorination provided a reference for controlling the reduction products of chlorinated alkenes and preventing the pollution caused by toxic intermediate products formed during incomplete dechlorination.

Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

Dechlorination processes attract great interest since they are involved in environmental protection and waste disposal technologies. In this paper, the process of gas-phase dechlorination of 1,2-dichloroethane, chloroform, and chlorobenzene over Ni/Al2O3 catalyst (90 wt% Ni) prepared by a coprecipitation technique was investigated. The reduction behavior of the oxide precursor NiO/Al2O3 was studied by thermogravimetric analysis in a hydrogen medium. A thermodynamic assessment of the conditions under which metallic nickel undergoes deactivation due to the formation of nickel chloride was performed. The dechlorination of chlorinated substrates was studied using a gravimetric flow-through system equipped with McBain balances in a wide range of temperatures (350–650 °C) and hydrogen concentrations (0–98 vol%). The impact of these parameters on selectivity towards the products of hydrodechlorination (C2H4, C2H6, and C6H6) and catalytic pyrolysis (carbon nanomaterial and CH4) was explored. The relationship between the mechanisms of the catalytic hydrodechlorination and the carbide cycle was discussed, and the specific reaction conditions for the implementation of both scenarios were revealed. According to the electron microscopy data, the carbonaceous products deposited on nickel particles during catalytic pyrolysis are represented by nanofibers with a disordered structure formed due to the peculiarity of the process including the side carbon methanation reaction.