A comparative study on degradation kinetics and toxicity changes of BPA and BPS in UV-based advanced oxidation
Noman Ali Shah1, Xiaobing Chen1, Ayesha Javed2
1State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun, 130117, China.
Abstract:
Bisphenol A (BPA) and Bisphenol S (BPS) are endocrine-disrupting chemicals that pose significant ecological and health risks due to their persistence and toxicity. This study presents a comprehensive comparison of three UV-based advanced oxidation processes (UV-AOPs: UV/Cl, UV/PDS, and UV/H2O2) for degrading BPA and BPS, with an emphasis on correlating degradation efficiency to the toxicity of transformation products (TPs). Using a 500 W mercury vapor lamp, we demonstrate how differences in electronic properties (e.g., BPA's electron-rich rings vs. BPS's electron-withdrawing sulfonyl group) influence radical selectivity (SO4•-, •OH, RCS) and by-product risks. The effects of oxidant dosage, pH, and dissolved organic matter were examined. The toxicity of degradation by-products was evaluated using an integrated approach combining ECOSAR predictions and Vibrio fischeri bioassays to reveal critical trade-offs between degradation rates and TP safety. The UV/PDS system demonstrated the highest BPA removal efficiency (96.5 % in 10 min, k = 0.3185 ± 0.034 min-1) under alkaline conditions, primarily via sulfate radicals (SO4•-). In contrast, BPS degradation was less efficient (k = 0.0910 min-1) due to the lower reactivity of its sulfonyl group. The UV/Cl process generated chlorinated by-products, such as TP07, with toxicity levels 1.5 to 2.0 times higher than the parent compounds, while UV/H2O2 produced hydroxylated by-products that were 25 % more toxic than BPA. Notably, chlorinated derivatives increased toxicity in BPA but reduced it in BPS due to steric hindrance from the sulfonyl group, a structural nuance not previously reported in AOP studies. Oxidized by-products were generally less toxic, whereas fragmented products exhibited higher toxicity than their precursors. These findings support pollutant-specific optimization of UV-AOPs, identifying UV/PDS as the most effective for BPA degradation while emphasizing the need for sulfonyl-targeted refinement in BPS treatment.
