Fast dechlorination of trichloroethylene by a bimetallic Fe(OH)2/Ni composite

Abstract

Trichloroethylene (TCE), one of the most frequently detected chlorinated organic pollutants (COPs) in groundwater, has potential risks to human health. The bimetallic system consisting of zero-valent iron (ZVI) and a second catalytic metal has been widely investigated for reductive dechlorination of COPs. However, the passivation layer of ZVI inhibits the electron transfer causing a low dechlorination efficiency. In this work, we designed a novel bimetallic system using Fe(OH)2 and Ni for fast dechlorination of TCE. The reduction efficiency of TCE reaches 94.8 % after 5 h of reaction in the Fe(OH)2/Ni system. TCE was completely dechlorinated to nontoxic gas products including ethylene and ethane, which was attributed to the generation of active hydrogen species (H*) in the system. The Ni2+ cations undergo the process of hydroxylation and olation. Subsequently, electrons of Fe(OH)2 were transferred to Ni(II) causing the formation of Ni(0). The catalytic Ni(0) sites generate H* for TCE dechlorination via catalytic reduction of H2O/H+. A part of Fe(II) in the Fe hydroxide layer of Fe(OH)2 was oxidized to Fe(III) leading to the formation of green rust with a hexagonal structure. Our work demonstrates Fe(OH)2/Ni is a promising composite material for the remediation of TCE-contaminated groundwater.