Degradation of bisphenol A during heat-activated peroxodisulfate treatment: kinetics, mechanism, and transformation products

Abstract

In this study, we systematically investigated the degradation kinetics, mechanism, and transformation products of bisphenol A (BPA) in a heat-activated peroxodisulfate (heat/PDS) system. The pseudo-first-order rate constants (kobs) values of BPA increased with initial PDS dosage (0-1.0 mM), temperature (50-65 °C), and solution pH (4.0-10.0). The presence of natural organic mater (NOM), chloride ion (Cl−), and bicarbonate ion (HCO3−) manifested inhibiting influence on the degradation of BPA during reaction, while nitrate (NO3−) was insignificant impact. According to radical scavenging experiments, the main oxidizing species were both hydroxyl radical (HO˙) and sulfate radical (SO4˙−), but the HO˙ played an important role. Transformation products were concentrated by solid phase extraction and identified by liquid chromatography high-resolution mass spectrometer (LC-HRMS). A total of fifteen transformation products derived from hydroxylation, demethylation, C-C bond cleavage, and dimerization reaction were identified. Further combining the quantum chemical calculation, the transformation pathways of BPA in the heat/PDS system were proposed. Toxicity analysis shows most of transformation products had less toxicity than that of BPA, indicating that oxidation of BPA by heat/PDS system was a detoxification process. These results illustrated that heat-activated PDS oxidation could be an efficient method to remove BPA from contaminated water.