Efficient degradation of sulfamonomethoxine in wastewater using a novel intimately coupled photocatalysis and biodegradation system prepared with the calcium alginate hydrogel

The insecure fixation of photocatalysts and their susceptibility to being covered by microorganisms existed in the traditional intimately coupled photocatalysis and biodegradation (ICPB) system. In this work, an ICPB system was developed by coupling g-C₃N₄ and biofilm carriers through introducing calcium alginate (CA) hydrogel. The ICPB-CA system showed superior removal efficiencies of sulfamonomethoxine (SMM) (99.3 %) compared to corresponding photocatalysis and biodegradation systems. Relatively higher stability was also achieved with SMM removal efficiencies higher than 92.5 % after three consecutive cycles, as CA hydrogel markedly improved the adhesion strength between the photocatalysts and biofilm carriers. Furthermore, SMM degradation pathways in the ICPB-CA system were proposed, with smaller-molecular products produced. Biotoxicity evaluation tests also indicated that the degradation products were less toxic than the parent SMM, suggesting that ICPB-CA system could significantly mitigate the antimicrobial activities of SMM. This study will provide a promising alternative to construct the ICPB system, realizing higher removal efficiency of antibiotics while decreasing their toxicity.