Mechanisms of enhanced oxidative degradation of tetrachloroethene by nano-magnetite catalysed with glutathione

Abstract

Abstract This work demonstrated the mechanisms of enhanced oxidative degradation of tetrachloroethene (PCE) by nano-magnetite (nano-Fe3O4) catalysed with glutathione (GSH). The changes of surface morphology and chemical composition of nano-Fe3O4 were examined by SEM-EDX and XRD analysis confirmed that the oxidation of nano-Fe3O4 to maghemite (γ-Fe2O3) occurred during the oxidative degradation of PCE. PCE was fully degraded in the nano-Fe3O4-GSH suspension at pH 7 in 4 hr. The oxidative degradation kinetic rate constant of PCE in the nano-Fe3O4-GSH suspension was 11.7 times faster (0.035 ± 0.01 h−1) than that in the nano-Fe3O4 suspension (0.003 ± 0.08 h−1), showing a potential role of GSH as a reductant to sustain redox of Fe3+ to Fe2+ and promote the generation of reactive oxygen species (ROS) (OH and O2− ) for the enhanced oxidative degradation of PCE by nano-Fe3O4. This coupling reaction mechanisms significantly enhanced the oxidative degradation kinetic rate constant of PCE in the nano-Fe3O4-GSH suspension. The oxidative degradation kinetic rate constant of PCE was predominantly controlled by the concentration of OH than the O2− in the nano-Fe3O4-GSH suspension. PCE was transformed to oxalic acid as major by-product via hydroxylation and oxidation reactions. The experimental findings could provide basic knowledge to identify the reaction mechanism for the enhanced oxidative degradation of chlorinated organic by biogeochemical reactions possibly observed in natural oxic-anoxic condition of hyporheic zone.