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 (k_obs) 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.