Enhanced degradation of carbamazepine by iron/S(IV) system using a novel S(IV) source

Abstract

• Potassium pyrosulfite (PPS) was a new S(IV) source as a precursor of sulfate radical. • O 2 was the key substance that caused the excellent performance of the system. • The relative contribution rates of SO 4 •− and HO • to CBZ degradation were 64% and 35% in the Fe 3+ /PPS system. • The small amount of ferric iron (60 μM) can effectively activate PPS. • Fe 3+ /Fe 2+ cycle can be realized in Fe 3+ /PPS system. Transition metal activation of sulfite (S(IV)) is a promising wastewater treatment technology. In this study, the activation of potassium pyrosulfite (PPS) with ferric iron (Fe 3+ ) is proposed firstly to degrade carbamazepine (CBZ). PPS has the advantages of low cost, non-toxicity and acidic solution, which makes it unnecessary to adjust the pH. The results showed that the Fe 3+ cycle was realized during the reaction process, and the degradation trend of CBZ was consistent with the formation rate of Fe 2+ and the decay rate of S(IV). Moreover, oxygen (O 2 ) plays a decisive role in the system and was the initiator of free radical chain reactions. The existence of sulfite radical (SO 3 •− ), sulfate radical (SO 4 •− ) and hydroxyl radicals (HO • ) in Fe 3+ /PPS system was proved by electron paramagnetic resonance (EPR), quenching experiments and terephthalic acid (TA) photoluminescence probing technique. The contribution of SO 4 •− and OH • to the removal of CBZ in Fe 3+ /PPS system is 64% and 35%, respectively. In addition, intermediates of CBZ were identified by Liquid Chromatography–Tandem Mass Spectrometry (LC–MS/MS) and possible removal pathways were also proposed. Finally, the effects of PPS concentration, Fe 3+ concentration, initial pH, anions and humic acid (HA) were also investigated.