Degradation of Chlorinated Contaminants at Mineral - Water Interface: The Engineered vs. Natural Surfaces of Sulfide Materials

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In this project funded by the Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation, Professors Weile Yan and Kayleigh Millerick from Texas Tech University (TTU) investigate a class of surface sulfided iron materials, which may have potential to degrade chlorinated molecules (specifically ethenes) in the sub-surface environment. It is hypothesized that controlled sulfidation of iron metal (Fe(0)) through chemical or biological means creates surfaces that have significantly enhanced reactivity towards chlorinated ethenes. This study explores the use of environmentally-compatible reactive surfaces for in situ abatement of persistent groundwater contaminants. This research provides a training ground for undergraduate and graduate researchers to engage in multidisciplinary investigations in environmental biogeochemistry and remediation. The findings are incorporated into a new course on Environmental Interfacial Chemistry. In addition, the investigators develop experiment kits and introduce the subject of groundwater contamination to K-12 students through science enrichment programs at TTU. The investigators take an integrated experimental approach to probe the relationship between the chemistry of the sulfided materials prepared under different conditions and the reactions of perchloroethene (PCE) and trichloroethene (TCE) on these reactive surfaces. Key factors controlling the rates and pathways of PCE and TCE degradation on these surfaces are elucidated through kinetic and isotopic investigations. The interface between a sulfided overlayer and an Fe(0) phase provides a sustained driving force against oxidative passivation in the environmental media. The transformation of surface sulfided iron and natural iron sulfides in groundwater environment, particularly under the influence of pertinent biogeochemical processes, are studied. This study advances the fundamental understanding of interactions between chlorinated ethenes and reactive surfaces that are either introduced by engineering intervention or naturally present in the subsurface environment. This study explores in situ abatement of persistent groundwater contaminants and trains undergraduate and graduate researchers to engage in multidisciplinary investigations in environmental biogeochemistry and remediation.