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Destruction of chlorinated hydrocarbons by zero-valent zinc and bimetallic zinc reductants in bench-scale investigations

Cushman, Christopher Scott
http://rave.ohiolink.edu/etdc/view?acc_num=wright1398342299

Abstract Details

2014, Master of Science (MS), Wright State University, Earth and Environmental Sciences.
Many remediation technologies have been developed to treat extensive subsurface contamination by chlorinated hydrocarbons (CHCs). One such technology is a permeable reactive barrier (PRB), which contains reactive media that acts as an electron donor in order to reduce CHCs. Extensive effort has been placed on finding the most suitable reactive media in PRBs, with zero-valent iron (ZVI) being the most commonly utilized media. However, zero-valent zinc (ZVZ) is a promising replacement for ZVI in PRBs as it will more readily donate electrons, resulting in more rapid degradation of CHCs. In addition, amending a secondary/catalytic metal to primary metal surface can result in increased degradation kinetics and yield of dechlorinated byproducts. In this investigation, chlorinated methanes (CF and DCM), ethanes (1,1,2,2-TeCA, 1,1,2-TCA, 1,1,1-TCA, and 1,2-DCA), ethenes (PCE, TCE, cis-DCE, trans-DCE, and VC) and propanes (1,2,3-TCP and 1,2-DCP) were reduced by ZVZ and Zn bimetallic reductants. Results indicated that Cu/Zn was a more potent bimetallic reductant than Pd/Zn and Ni/Zn due to impressive CF degradation kinetics and increased yield of methane formed via direct transformation of CF to methane. Cu/Zn was used in reduction of all other compounds and did not significantly change byproduct distributions when compared to ZVZ. Reductive β-elimination was an important degradation pathway observed for chlorinated ethanes and ethenes, with reduction of chlorinated ethenes via this pathway resulting in the formation of highly reactive chlorinated acetylene intermediates, thus preventing the formation of VC. It appears that ZVI will reduce chlorinated ethenes via reductive β-elimination more readily than Zn reductants, suggesting an advantage of ZVI in the reduction of chlorinated ethenes. However, Zn reductants appear to be well suited for PRB applications at sites contaminated with 1,2,3-TCP, as reduction with Zn reductants yields fully dechlorinated byproducts via a reductive β-elimination to hydrogenolysis sequence, unlike ZVI. Cu/Zn increased degradation kinetics compared to ZVZ for all CHCs investigated, but only slight enhancement in kinetics was observed for chlorinated propanes. Increased chlorinated methane, ethane, and propane kinetics have been reported with ZVZ when compared to ZVI, thus suggesting the need to further study Cu/Zn as a potential replacement for ZVI in PRB applications.
Abinash Agrawal, Ph.D. (Advisor)
Mark Goltz, Ph.D. (Committee Member)
Songlin Cheng, Ph.D. (Committee Member)
140 p.
Chemistry; Environmental Engineering; Environmental Geology; Environmental Management; Environmental Science; Environmental Studies; Organic Chemistry; Sustainability; Water Resource Management
chlorinated hydrocarbons; zero-valent zinc; ZVZ; zero-valent iron; ZVI; bimetallic; reductants; copper; Cu-Zn; palladium; Pd-Zn; nickel; Ni-Zn; chlorinated methanes; chlorinated ethanes; chlorinated ethenes; chlorinated propanes; 1,2,3-TCP

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Citations

  • Cushman, C. S. (2014). Destruction of chlorinated hydrocarbons by zero-valent zinc and bimetallic zinc reductants in bench-scale investigations [Master's thesis, Wright State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=wright1398342299

    APA Style (7th edition)

  • Cushman, Christopher. Destruction of chlorinated hydrocarbons by zero-valent zinc and bimetallic zinc reductants in bench-scale investigations. 2014. Wright State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=wright1398342299.

    MLA Style (8th edition)

  • Cushman, Christopher. "Destruction of chlorinated hydrocarbons by zero-valent zinc and bimetallic zinc reductants in bench-scale investigations." Master's thesis, Wright State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1398342299

    Chicago Manual of Style (17th edition)

wright1398342299
708
© 2014, all rights reserved.
This open access ETD is published by Wright State University and OhioLINK.