Oxidative removal of Bisphenol A by UV-C/peroxymonosulfate (PMS): Kinetics, influence of co-existing chemicals and degradation pathway

In the present study, a sulfate radical-based advanced oxidation process was applied for the degradation of an industrial chemical and suspected endocrine disruptor, Bisphenol A (BPA). UV-C (lambda = 254 nm; 40 W power; I-o = 1.26 mu E s(-1)) activated peroxymonosulfate (PMS) was used as an oxidant. The effect of operating parameters (initial concentration of BPA, dose of PMS, initial solution pH (pH(o)), and water matrix components such as chloride (Cl-), bicarbonate (HCO3-) ions and humic acid (HA) was evaluated. At the initial pH of reaction mixture (5.15) and room temperature (29 +/- 3 degrees C), the optimum dosage of PMS was found to be 0.66 mM, giving a BPA removal of 96.7 +/- 0.05% and a total organic carbon (TOC) removal of 72.5 +/- 0.05% after 360 mm of irradiation. With an increase in initial BPA concentration and PMS dosage greater than 0.66 mM, the BPA and TOC removal decreased. The extent of BPA removal increased with an increase in pH(o) (3 <= pH(o) <= 12) of the reaction mixture. The degradation of BPA followed pseudo-first-order kinetics and the apparent first order rate constant for BPA was found to be 0.025 min(-1) at the optimum oxidation conditions (C-BPA = 0.22 mM, C-PMS = 0.66 mM, pH = 5.15, temperature = 29 +/- 3 degrees C). The Cl- ions have negligible inhibition effect on the BPA removal. However, the HCO3- and HA inhibited the BPA oxidation under UV-C irradiation. The identification of intermediates and final products was carried out with HPLC, GC/MS and FTIR, and a degradation pathway was proposed. The present study reveals that the UV-C/PMS oxidation process is effective for BPA removal under real water/wastewater conditions. (C) 2015 Elsevier B.V. All rights reserved.