First assessment on degradability of sodium p-perfluorous nonenoxybenzene sulfonate (OBS), a high volume alternative to perfluorooctane sulfonate in fire-fighting foams and oil production agents in China

Abstract

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) is widely used in China as fire-fighting foam co-formulant and oil production agent, because it is an economical alternative to perfluorooctane sulfonate (PFOS), classified as persistent organic pollutant by the Stockholm Convention. Such chemical very likely possesses toxicological and bioaccumulative characteristics that are similar to PFOS and many other perfluorinated compounds. However, in this first report we demonstrate that OBS, in spite of its non-readily biodegradability, can be decomposed by UV/H₂O₂ or even sole UV (254 nm) system (contrary to PFOS). More than 96% OBS is degraded in aqueous solution within 20 minutes by both methods thanks to its peculiar molecular structure. Yet, after 2 h reaction UV/H₂O₂ gives 99% sulfate recovery, while in UV system only 61% sulfate is detected; fluoride recovery was less than 16% for both treatments. Such results, corroborated by intermediate identification, highlight that UV/H₂O₂ system can effectively destroy the OBS sulfonated aromatic moiety. On contrary, it remains intact in several products of the UV treatment, raising a concern on their potential toxicity. Such results demonstrate OBS better degradability and treatability, compared to other perfluorinated chemicals, and suggest that it might be biodegraded on long term. Moreover, these findings may be of help for a more environmentally friendly eco-design of other fluorinated alternatives.