Trichloroethylene dechlorination rates, pathways, and efficiencies of ZVMg/C in aqueous solution

The removal mechanism from the reductive dechlorination of trichloroethylene (TCE) by zero valent magnesium (ZVMg) in aqueous solution is systematically studied. Following the preparation and characterization of ball-milled micro ZVMg with graphite (ZVMg/C) particles, this paper evaluated the TCE reaction rates, pathways, utilization rates and aging effects of ZVMg/C particles in aqueous solution under uncontrolled pH conditions. Overall, 38 μM of TCE was transformed by 10 g/L of ZVMg/C to methane (62.51%) and n-hexane (11.86%) and ethane (7.40%) and other alkene and alkyne products through the catalytic hydrogenation pathway. The measured surface area normalized pseudo-first order rate constants (K_SA) were up to 9.31 × 10^-2 L/m²/h and the utilization rate of Mg⁰ accounted for around 60%. The K_SA were decreased to 1.90 × 10^-2 L/m²/h in case of ZVMg/C being exposed in the atmosphere for 6 days due to 7.3% reduction in the utilization rate of Mg⁰ from the initial 85.2%, and 5.11 × 10^-2 L/m² h in case of ZVMg/C aged in water for one day. The removal efficiencies of approximately 56%, 58% and 87% by 10 g/L of ZVMg/C were achieved in the contaminated groundwater comprising 38 μM of TCE, 43 μM of 1,2-dichlorobenzene and 8.12 μM of trichlormethane. Therefore, it is concluded that ZVMg/C is viewed as a potential and effective remediation reagent for the groundwater remediation.