UV absorbance and electron donating capacity as surrogate parameters to indicate the abatement of micropollutants during the oxidation of Fe(II)/PMS and Mn(II)/NTA/PMS

In this study, the relative residual UV absorbance (UV 254 ) and/or electron donating capacity (EDC) was investigated as a surrogate parameter to evaluate the abatement of micropollutants during the Fe(II)/PMS and Mn(II)/NTA/PMS processes. In the Fe(II)/PMS process, UV 254 and EDC abatement was greater at pH 5, which was attributed to the generation of SO 4 • − and •OH at acidic pH. In the Mn(II)/NTA/PMS process, UV 254 abatement was greater at pH 7 and 9, while EDC abatement was greater at pH 5 and 7. This was due to the fact that MnO 2 was formed at alkaline pH to remove UV 254 by coagulation processes, and the manganese intermediates (Mn(V)) were formed at acidic pH to remove EDC via electron transfer processes. Due to the strong oxidation capacity of free radicals (SO 4 • − and •OH) and manganese intermediates (Mn(V)) in the Fe(II)/PMS and Mn(II)/NTA/PMS processes, respectively, the abatement of micropollutants increased with increasing dosages of oxidant in three different waters at neutral pH. In the Fe(II)/PMS and Mn(II)/NTA/PMS processes, except for nitrobenzene (NB) (approximately 23% and 40%, respectively), the removal of other micropollutants was in excess of 70% when the oxidant dosages were greater (100 µM and 80 µM, respectively) in different waters. The linear relationship between the relative residual UV 254 , EDC and the removal of micropollutants was established in different waters, showing a one-phase or two-phase linear relationship. The differences of the slopes for one-phase linear correlation in the Fe(II)/PMS process (micropollutant-UV 254 0.36–2.89, micropollutant-EDC: 0.26–1.75) were less than that in the Mn(II)/NTA/PMS process (micropollutant-UV 254 0.40–13.16, micropollutant-EDC: 0.51–8.39). Overall, these results suggest that the relative residual UV 254 and EDC could truly reflect the removal of micropollutants during the Fe(II)/PMS and Mn(II)/NTA/PMS processes.