Insights into the photocatalytic activation of peroxymonosulfate by visible light over BiOBr-cyclodextrin polymer complexes for efficient degradation of dye pollutants in water

The combination of adsorption-photocatalysis and advanced oxidation processes (AOP) based on sulfate (SO 4 •− ) for the treatment of organic pollution has the advantages of a high degradation rate, affordability, and an absence of secondary pollution. This study combined amphiphilic super-crosslinked porous cyclodextrin resin (PBCD-B-D), bismuth oxybromide (BiOBr), a composite material with dual functions of adsorption and photocatalysis, and AOP based on SO 4 •− for the treatment of Acid Orange 7 (AO7) in water. The combination of BiOBr/PBCD-B-D (BOP-24) with peroxymonosulfate (PMS) showed an optimal adsorption–photocatalytic effect. Compared to the 24% PBCD-B-D (BOP-24)/visible light system, the degradation efficiency of BOP-24/PMS system for AO7 is increased from 64.1% to 99.2% within shorter time (∼60 min). Moreover, the BOP-24/PMS system showed a wide range of pH application (pH = 3–11). The addition of Cl −, SO 4 2−, and NO 3 − promoted the photodegradation of AO7, whereas the addition of CO 3 2− did not. The free radical capture experiments of the BOP-24/PMS AO7 degradation system showed that •O 2 −, h +, •OH, and SO 4 •− are reactive species. The proposed BOP-24 system used adsorption and a unique cavity structure to enrich AO7 near the active site, thereby reducing the path for PMS activation. PMS also acted as an electron (e − ) acceptor to promote the transfer of part of e − to PMS, thereby further improving the efficiency of carrier separation. The proposed system is an effective method to improve the degradation of pollutants and broadens the range of application of SO 4 •− -based AOP technology.