Kinetics and mechanisms of non-radically and radically induced degradation of bisphenol A in a peroxymonosulfate-chloride system

Bisphenol A, a hazardous endocrine disruptor, poses significant environmental and human health threats, demanding efficient removal approaches. Traditional biological methods struggle to treat BPA wastewater with high chloride (Cl^-) levels due to the toxicity of high Cl^- to microorganisms. While persulfate-based advanced oxidation processes (PS-AOPs) have shown promise in removing BPA from high Cl^- wastewater, their widespread application is always limited by the high energy and chemical usage costs. Here we show that peroxymonosulfate (PMS) degrades BPA in situ under high Cl^- concentrations. BPA was completely removed in 30 min with 0.3 mM PMS and 60 mM Cl^-. Non-radical reactive species, notably free chlorine species, including dissolved Cl₂(l), HClO, and ClO^- dominate the removal of BPA at temperatures ranging from 15 to 60 °C. Besides, free radicals, including ^•OH and Cl₂ ^•-, contribute minimally to BPA removal at 60 °C. Based on the elementary kinetic models, the production rate constant of Cl₂(l) (32.5 M^-1 s^-1) is much higher than HClO (6.5 × 10^-4 M^-1 s^-1), and its degradation rate with BPA (2 × 10⁷ M^-1 s^-1) is also much faster than HClO (18 M^-1 s^-1). Furthermore, the degradation of BPA by Cl₂(l) and HClO were enlarged by 10- and 18-fold at 60 °C compared to room temperature, suggesting waste heat utilization can enhance treatment performance. Overall, this research provides valuable insights into the effectiveness of direct PMS introduction for removing organic micropollutants from high Cl^- wastewater. It further underscores the critical kinetics and mechanisms within the PMS/Cl⁻ system, presenting a cost-effective and environmentally sustainable alternative for wastewater treatment.