Novel tetrahedral Ag3PO4@N-rGO for photocatalytic detoxification of sulfamethoxazole: Process optimization, transformation pathways and biotoxicity assessment

Global spreading of antibiotic resistant microorganisms and genes calls for the development of effective strategy to eliminate antibiotic pollution from the environment. Tetrahedral silver phosphate (Ag3PO4) is one of the master visible light photocatalysts but encountered the drawback of low stability due to photocorrosion. Integration of Ag3PO4 with N-doped reduced graphene oxide (N-rGO) that has large specific surface area, ample functional groups and hetero atoms doping is anticipated to overcome the problem. Thus, the present study prepared high stability Ag3PO4@N-rGO hybrid catalysts and applied for detoxification of sulfamethoxazole (SMX). Further, the operational parameters towards the photocatalytic degradation was systematically optimized to maximize the efficiency through response surface methodology (RSM) based on central composite design (CCD). The parameters that influenced the SMX degradation efficiency was as follows: pH > N-content > catalyst dosage. Under the optimal conditions (catalyst dosage = 0.2 g/L, pH = 5.8, and N-content of 5.14%), 93.8% of SMX degradation was obtained within 60 min. The plausible degradation products generation during the photocatalytic degradation of SMX was analyzed by LC-ESI/MS and the degradation pathway was proposed. In addition, the toxicity of the degradation products was investigated through Escherichia coli colony forming unit assay and a substantial biotoxicity reduction by this photodegradation was observed.