Environmental Chemistry Research
Faculty Member: Dr. Peter Vikesland
Many chemical reactions of environmental significance occur at the surface of metal oxides. Although a great deal is known about a number of these reactions, continuing research is required to better understand the role these oxides play in determining the fate of an ever-expanding number of reactive chemicals. Our previous research in this area has illustrated that the presence of metal oxides enhances the reactivity of redox active species such as Fe(II) and natural organic matter with aqueous oxidants. Additional work has examined the role of metal oxide formation on the long-term viability of cast iron (Fe(0)) based treatment schemes. This work has shown that different inorganic and organic species alter the chemistry of the metal-solution interface, and that these alterations may need to be considered when designing treatment strategies that employ cast iron.
Reduced P in the Environment and Its Role in Anaerobic Iron Corrosion
Faculty Member: Dr. Marc Edwards
Phosphorus chemistry controls keys aspects of eutrophication, microbial nutrition, corrosion and other environmental processes. We propose a three phase study of environmental phosphorus chemistry that will 1) survey the relative importance of reduced phosphorus in representative environmental samples, 2) explore mechanisms of reduced phosphorus formation in biotic and abiotic systems, and 3) define the catalytic role of reduced phosphorus in iron corrosion. Since the presence of reduced phosphorus in the environment directly contradicts a central assumption of our field, we have conducted preliminary experimental results that prove phosphite can leach to potable drinking water from corroding iron pipe at the mg/L level and that hypophosphite profoundly alters anaerobic iron corrosion rates.
The first phase of work refines existing gas and ion chromatography techniques to quantify reduced phosphorus in solid, liquid and gas samples. The second phase of work examines mechanisms of orthophosphate reduction to phosphites and phosphides. Finally, it has long been known that catastrophic iron corrosion sometimes occurs in the presence of sulfate reducing bacteria (SRB) with profound economic, health and aesthetic consequences. SRB have been identified in scale (rust) layers present on iron pipes in all water distribution systems. We propose a theory of SRB-induced iron corrosion that is based on the observations that 1) reduced phosphorus species such as phosphine (PH3) can catalyze the rate limiting reaction in iron corrosion, and 2) phosphates added to iron metal or drinking water as corrosion inhibitors can serve as the source of this catalyst in the presence of sulfides. If confirmed, our theory has profound implications for water utilities who may be unwittingly worsening iron corrosion using “best available” preventative measures.