Degradation Characteristics of Carbon Tetrachloride by Granular Sponge Zero Valent Iron

Abstract

Granular sponge zero valent iron (ZVI) was employed to degrade carbon tetrachloride (CCl4). The effects of acidic washing, initial solution pH, and ZVI dosage on CCl4 degradation were investigated. Results showed that CCl4 was effectively removed by ZVI and approximately 75% of CCl4 was transformed into chloroform through hydrogenolysis. The rate of chloroform transformation was slower compared to that of CCl4, resulting in chloroform accumulation. CCl4 degradation was a pseudo first-order process. The observed pseudo first-order reaction rate constant (kobs) for CCl4 and chloroform were 0.1139 and 0.0109 h−1, respectively, with a ZVI dosage of 20 g/L and an initial CCl4 concentration of 20 mg/L. Surface acidic washing had a negligible effect on CCl4 degradation with ZVI. The kobs for CCl4 degradation increased linearly with increasing ZVI dosage and the optimal dosage of ZVI was 20 g/L based on the surface area-normalized rate constants. The negative relationship between kobs and the solution pH indicated that the degradation of CCl4 by ZVI performed better under weakly acidic conditions.

Remediation of chloroform in fine‐textured soil using zero‐valent iron

“…According to our speculative pathway (Supporting Information: (Feng & Lim, 2005;Gillham & O'Hannesin, 1994;Matheson & Tratnyek, 1994;Zhu et al, 2021), possibly due to greater carbon-chlorine bond strength in less chlorinated compounds (Huang et al, 2012).…”

“…Nanoscale Fe 0 has higher reactivity due to its increased reactive surface areas toward a variety of chlorinated contaminants (Zhu et al, 2021). The type of Fe 0 can also affect the transformation pathway and resulting products.…”

“…The transformation of chloroform and the production of dichloromethane, chloromethane, and methane in our study illustrated a hydrogenolysis pathway (Supporting Information: Figure S1A). Earlier studies reported the transformation of carbon tetrachloride and chloroform through a common hydrogenolysis pathway (Feng & Lim, 2005;Matheson & Tratnyek, 1994;Zhu et al, 2021) or sometimes in combination with other carbide hydrolysis and carbon reduction pathways (McCormick & Adriaens, 2004). However, the simultaneous production of dichloromethane, chloromethane, and methane during the transformation of chloroform in our simple matrix microcosm (Supporting Information: Figure S2B,C) clearly depicts that the hydrogenolysis pathway was not sequential (chloroform to dichloromethane to chloromethane to methane) suggesting the direct transformation of chloroform to dichloromethane, chloromethane, or methane (Supporting Information: Figure S1B).…”

“…However, halorespiration is mostly carried out by specialized bacteria not common in the environment (Wang et al, 2022). Application of nanoscale zero‐valent iron (Fe 0 ) has been used in soil and groundwater remediation (Jin et al, 2018; Lv et al, 2020; Zhu et al, 2021), where it acts as a reducing agent donating electrons to transform halogenated contaminants into less toxic forms. The size and high reactivity of Fe 0 nanoparticles make them favorable for the remediation of water and soils as nanoparticles can infiltrate into very small soil pores and persist suspended in groundwater, allowing movement away from the injection point (Chapman et al, 2020; Galdames et al, 2020).…”

“…Most research focused on the reductive chlorination of chlorinated ethenes, such as perchloroethylene and trichloroethylene by Fe 0 . A few studies showed the application of Fe 0 for the dechlorination of chlorinated methanes and were generally related to carbon tetrachloride (Jin et al, 2018; Lv et al, 2020; Zhu et al, 2021). Most of these studies showed transformation to dichloromethane only and none showed long‐term observations for natural attenuation.…”