Visible light activation of persulfate by α-Fe2O3/PDINH photocatalyst for sulfamethoxazole degradation

Abstract

Self-made α-Fe2O3 and commercially perylene diimide (PDINH) were selected to prepare α-Fe2O3/PDINH composite photocatalysts (FPx, where x represents the mass percentage of PDINH), and these were utilized for the activation of peroxydisulfate (PDS) to degrade sulfamethoxazole (SMX) in water under visible light. The FP3/PDS/vis system was able to remove about 98.9 % of SMX in 140 min, and the corresponding reaction rate reached 0.0327 min−1, for 23.4 and 18.2 times greater than α-Fe2O3/PDS/vis system and the PDINH/PDS/vis system, respectively. PDS played a major role in SMX degrading and both free radical (SO4−, OH, O2−) and non-free radical (1O2, h+) were involved in the removal of SMX. Interestingly, with the exception of h+, all radicals and non-radicals were directly or indirectly derived from PDS activation rather than photocatalysis. Besides, 3 degradation pathways and 13 by-products of SMX were identified, and the toxicity analyses of the intermediates demonstrated that the FPx/PDS/vis system could effectively remove SMX from water and reduce its biotoxicity. This work offers insights into the photocatalytic activation of PDS for removing SMX from water.