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Accelerated decomposition of halogenated compounds

| By Mary Page Bailey

A new research partnership between the Water Environment & Reuse Foundation (WERF; Alexandria, Va.; and the University of Texas at Arlington (UTA; seeks to tackle one of the most challenging and persistent water contaminants — perfluorooctane sulfonate (PFOS). Current industrial methods for treating PFOS in water involve physical removal via membrane separation or adsorption process, but there are no widely used chemical degradation processes due to the difficulties associated with removing halogen atoms. Although halogenated compounds are highly resistant to chemical oxidation, research published in Environmental Engineering Science showed that introducing a preliminary chemical reduction step prior to oxidation may enhance PFOS decomposition. The initial chemical reduction step strips off the fluorine, weakening the compound and making it more vulnerable to oxidation.

This strategy — known as advanced oxidation integrated with reduction, or AIR — will employ zero-valent iron (ZVI) conjugated with common oxidants. According to the team, well-dispersed ZVI nanoparticles (Fe0) chemically reduce PFOS while oxidizing and transforming into Fe2+ and Fe3+, at which point the Fe ions can activate added oxidants to produce hydroxyl and sulfate radicals that attack and decompose PFOS via oxidation routes. The team will continue to investigate if this combination of oxidative decomposition with reductive dehalogenation would be effective in large-scale PFOS degradation. The team believes that the AIR process could be easily scaled up, but that the costs to acquire large quantities of ZVI might pose some issues. This research is slated for completion in the Fall of 2018.