Hydrogen sulfite promoted the activation of persulfate by μM Fe2+ for bisphenol A degradation.

This study evaluated the improvement of bisphenol A (BPA) elimination through hydrogen sulfite (HS) coupling with persulfate (PS) activated by low amounts of Fe2+. Under the optimum condition (10 μM Fe2+, 0.6 mM HS, 0.8 mM PS, pH = 4.0), 100% BPA (5 μM) was removed within 15 min. Sulfate radical (SO4•-) and singlet oxygen (1O2) were confirmed as the primary active species for BPA degradation in the Fe2+/HS/PS system, and the steady-state concentration of SO4•- and 1O2 was 2.43 × 10-9 M and 1.67 × 10-9 M, respectively. Besides, FeHSO3+ and FeOHSO3H+ were the main iron species in the Fe2+/HS/PS system. The removal potency of BPA depended on the operation parameters, such as chemical reagent dosages, reaction temperature, and the solution initial pH. The impact of NO3-, SO42-, and humic acid (HA) on BPA removal was negligible, whereas Cl-, HCO3-, and HPO42- restrained BPA decomposition. Two injections of HS could improve the limitation of BPA degradation efficiency due to the rapid consumption of HS in the reaction process. The lower removal efficiency of BPA was observed in real water matrices than that in ultrapure water. Whatever, up to 58.1%, 66.3%, 68.1%, and 88.1% of BPA were removed from domestic wastewater, lake water, river water, and tap water within 10 min, respectively. In addition, the BPA degradation process was characterized by the 3D fluorescence spectra technique, which indicated the BPA oxidation intermediates also have fluorescence characteristics. Moreover, 6 intermediate products were identified, and the possible degradation pathways of BPA were proposed. Additionally, the Fe2+/HS/PS system also exerted an excellent performance for the removal of other representative organic contaminants including enrofloxacin, acid orange 7, acetaminophen, and phenol. All results indicated that the Fe2+/HS/PS system could be a promising method for organic pollutant removal.