11/21/2023
By Danielle Fretwell

The Francis College of Engineering, Department of Civil and Environmental Engineering, invites you to attend a Doctoral Dissertation Proposal defense by Lingfei Fan on "Abiotic Transformation of Halogenated Contaminants and A reactive Sampler for Quantifying Reaction Rates."

Candidate Name: Lingfei Fan
Degree: Doctoral
Defense Date: Thursday, Nov. 30, 2023
Time: 2 to 4 p.m. EST
Location: Shah Hall, Room 200Y

Committee:

  • Advisor Weile Yan, Associate Professor, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Clifford Bruell, Professor, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Xiaoqi Zhang, Professor, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Kwok-Fan Chow, Associate Professor, Department of Chemistry, University of Massachusetts Lowell

Brief Abstract:
Chlorinated solvents are the most commonly detected and persistent contaminants in the underground environment. At contaminated sites, it is difficult to quantify the efficacy of abiotic dechlorination in the field due to the co-occurrence of microbial dechlorination and other processes that lead to contaminant attenuation. As a result, significant uncertainty exists regarding the long-term persistence of chlorinated solvents at complex sites. Various forms of zerovalent iron (ZVI) materials have been used to degrade chlorinated solvents, but most lab studies focus on the reactions of trichloroethene. The performance on other commonly detected chlorinated solvents is less well characterized. In this study, we investigate the degradation rates of perchloroethene (PCE), dichloroethane isomers (DCEs) and vinyl chloride (VC) using sulfur-amended nano-ZVI (S-nZVI) and bulk ZVI (S-ZVI). The experimental results indicate that, the rates of PCE and DCEs degradation were accelerated by 2 to 10 folds when S-nZVI was used in place of the unmodified nZVI, suggesting the enhancement effect varies with different chlorinated contaminants. Increasing the sulfur dosage (i.e., the S/Fe ratio increasing from 0.0013 to 0.5) has a moderate effect on the reaction rates. On the contrary, the application of S-ZVI posted a hindering effect on the degradation rate of VC, exhibiting a rate at least six times slower than that observed with unmodified ZVI. To assess the abiotic dechlorination rates at remediation sites, we developed an in situ reactive sampling probe to capture acetylene, the latter a unique product of abiotic dechlorination of PCE and TCE. The reactive probe is based on copper-catalyzed cycloaddition between terminal alkyne and azide groups, also known as CuAAC click chemistry. This reaction is highly specific and it produces a stable triazole product at a quantitative yield, thereby permitting a sampling scheme to capture acetylene arising in the underground environment for quantitation. Laboratory microcosm results demonstrated that this azide-based acetylene sampling tool can provide sensitive and quantitative measurement of acetylene formed during TCE dechlorination, with potential applications in groundwater monitoring and remediation.