Sulfolane reduction by arginine and ferrous iron ions

Abstract

Sulfolane is a water-miscible, bioavailable, worldwide pollutant. While its aerobic biodegradation by bacteria is well documented, its abiotic degradation by amino acids and metal ions has never been reported. Here we find that Fe^2 + and arginine (ARG) reduce sulfolane to sulfoxide at circum-neutral pH, as shown by attenuated total reflection-Fourier transform infrared spectroscopy. Sulfolane reduction occurs at the surface of iron-ARG solid flocs, onto which sulfoxide remains sorbed even after rinsing with water volumes up to 16-fold the floc volume. Sulfolane reduction by Fe²⁺ ions does not occur in the absence of ARG, which binds iron and affects its redox chemistry, as shown by cyclic voltammetry. Sulfolane reduction is also promoted by lysine, but not by histidine. Sulfolane is not reduced by Fe³⁺ and ARG, indicating that this reaction requires Fe²⁺ oxidation to Fe³⁺. The observed abiotic transformation of sulfolane may affect its fate in natural ecosystems.