Efficient removal of bisphenol A by superoxide radical and singlet oxygen generated from peroxymonosulfate activated with Fe0-montmorillonite

For eliminating organic pollutants from wastewater, Fe 0 or Fe 0 -composites as catalyst for peroxymonosulfate (PMS) activation have attracted increasing attention in advanced oxidation processes. In this work, a novel Fe 0 -montmorillonite composites (Fe-Mt-C-H 2 ) have been prepared by thermal reduction and used as an activator for PMS to remove bisphenol A (BPA). The removal efficiency of BPA (25 mg·L −1 ) and total organic carbon (TOC) were 99.3% and 70.6%, respectively, in the presence of Fe-Mt-C-H 2 (0.4 g·L −1 ) and PMS (1 mM) at pH of 3. Electron paramagnetic resonance (EPR) spectroscopy and radical scavenger studies demonstrated that superoxide radical (O 2 − ) and singlet oxygen ( 1 O 2 ) were the crucial reactive oxygen species (ROS) in the Fe-Mt-C-H 2 /PMS system rather than sulfate (SO 4 − ) and hydroxyl radical (·OH). Besides, it was found that pH had a great influence on the catalytic oxidation rate of BPA and the Fe-Mt-C-H 2 exhibited best catalytic performance and reusability at initial pH of 3. Furthermore, the constituents of the iron surface oxidation layer at different initial pH were investigated with X-ray photoelectron spectroscopy studies, which indicated that the major constituents were Fe 3 O 4 in acidic solution and contained α-Fe 2 O 3 , FeO and FeSO 4 (s) in alkaline or neutral solution. The findings of this study provide new insights into the activation mechanism of PMS by Fe 0 -composites and exhibit a promising application of Fe-Mt-C-H 2 in wastewater treatment.