Micropollutants removal by heterogeneous advanced oxidation process: Tentative identification of transformation products, degradation profile and ranking based on (Q)SAR risk assessment by multi-criteria techniques

This study assessed the use of a heterogeneous advanced oxidation process as treatment to remove four micropollutants (sulfamethoxazole (SMX), diclofenac (DCF), carbamazepine (CBZ) and trimethoprim (TMP)). The treatment was based on the activation of peroxymonosulfate (PMS) by iron-modified biochar (Fe-BC) under sunlight. The results showed that Fe-BC (0.25 g/L) coupled with PMS (0.1 mM) under sunlight degraded > 80 % of micropollutants within 10 min in demineralized water. For secondary effluent treatment, Fe-BC and PMS concentrations were increased to 1 g/L and 0.5 mM, achieving > 80 % degradation of all micropollutants within 120 min. 26 transformation products (TPs) were tentatively identified via suspect screening analysis by LC-QTOF MS. (Q)SAR predictions of TPs, combined with multi-criteria decision-making (MCDM) techniques, showed that of the eight endpoints investigated, only three (biodegradability, estrogen receptor binding, and non-mutagenic score) were the most relevant for global risk. Finally, TOPSIS ranking showed SMX (1st) and TP SMX 268 (A or B) (2nd) (increasingly generated during treatment) were the compounds that posed higher risks. Besides SMX, the first 9 in ranking were TPs, showing they have higher risks associated than the parent compound. Thus, they must be monitored to better set operating conditions of treatment (such as treatment time) to ensure safer effluent.