Targeted modulation of g-CN photocatalytic performance for pharmaceutical pollutants in water using ZnFe-LDH derived mixed metal oxides: Structure-activity and mechanism.

Pharmaceuticals have been frequently detected in various water bodies, posing potential threat to human health and ecological environment. In this work, ZnFe-LDH derived mixed metal oxides (ZnO/ZnFeO, ZnFeMMO) were innovatively adopted to modulate the g-CN photocatalytic performance for the enhanced degradation of ibuprofen (IBF) and sulfadiazine (SDZ) as targeted pollutants. Characterization analyses indicated that the g-CN/ZnFeMMO composites were in the feature of rationally-designed microarchitecture, increased specific surface area, improved light absorbance and efficient charge separation, thereby resulting in promoted photocatalytic activities. Furthermore, the ratio of g-CN to ZnFeMMO in the composites was found to exert significant effects on the resulted microstructures and properties. The results showed that the composite with low g-CN content of 1.0 wt% or high g-CN content of 90 wt% exhibited the optimum catalytic activity for the degradation of IBF or SDZ, respectively. Such distinct structure-activities can be attributed to the different dominated reactive species in two cases: h for IBF degradation but OH for SDZ degradation. A Z-scheme mechanism was proposed for the charge separation, together with ZnFeO as a light sensitizer. Degradation pathways for IBF and SDZ were established by ESI-QToF-MS technology. This work provided a new perspective to develop rationally-architectured g-CN based photocatalysts for the decontamination of water polluted by pharmaceuticals.