Efficient removal of estrogenic compounds in water by MnIII-activated peroxymonosulfate: Mechanisms and application in sewage treatment plant water

In this paper, the degradation of three endocrine-disrupting chemicals (EDCs): bisphenol A (BPA), 17 beta-estradiol (E2) and 17 alpha-ethinylestradiol (EE2) by manganite (gamma-MnOOH) activated peroxymonosulfate (PMS) was investigated. Preliminary optimisation experiments showed that complete degradation of the three EDCs was achieved after 30 mM of reaction using 0.1 g L-1 of gamma-MnOOH and 2 mM of PMS. The degradation rate constants were determined to be 0.20, 0.22 and 0.15 min(-1) for BPA, E2 and EE2, respectively. Combining radical scavenging approaches, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses, we revealed for the first time that about 40% of EDCs degradation can be attributed to heterogeneous electron transfer reaction involving freshly generated Mn(IV), and 60% to sulfate radical degradation pathway. The influence of various inorganic ions on the gamma-MnOOH/PMS system indicated that removal efficiency was slightly affected by chloride and carbonate ions, while nitrate and nitrite ions had negligible impacts. The application of gamma-MnOOH/PMS system in real sewage treatment plant water (STPW) showed that degradation rate constants of EDCs decreased to 0.035-0.048 min(-1 )and complete degradation of the three EDCs after 45 mM. This study provides new insights into the reactivity of combined gamma-MnOOH and PMS, and opens new ways for the application of Mn-bearing species in wastewater treatment technologies.