Enhanced bio-photodegradation of p-chlorophenol by CdS/g-C₃N₄ 3D semiconductor-microbe interfaces

p-chlorophenol (p-CP), one of the highly toxic chlorinated organic compounds, is recalcitrant in conventional biodegradation process. This study reported a synergistic degradation protocol of 3D semiconductor-microbe interfaces, in which graphite felts (GF) and CdS/g-C₃N₄ nanocomposites were chosen as the carrier and semiconductor for enhanced p-CP degradation. Based on microstructure, photoelectrochemical and degradation performance analysis, the optimal CdS content in CdS/g-C₃N₄ nanocomposites was 10 wt%. The efficiencies of p-CP and TOC removal in bio-photodegradation system were as high as 95% and 77% without extra electron acceptors/donors, which were far better than those in traditional photodegradation and biodegradation system. High-throughput sequencing analysis suggested that p-CP degradation related species (Chryseobacterium, Stenotrophomonas and Rhodopseudomonas), electroactive species (Chryseobacterium, Stenotrophomonas, Hydrogenophaga and Cupriavidus) and hydrogen-utilizing species (Hydrogenophaga and Cupriavidus) were enriched at 3D semiconductor-microbe interfaces. The enrichment of functional species played a crucial role for p-CP removal and mineralization at 3D semiconductor-microbe interfaces. Moreover, the mechanism of enhanced p-CP bio-photodegradation at 3D semiconductor-microbe interfaces was investigated by utilizing Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2). The results showed that the genes involved in p-CP biodegradation, hydrogen metabolism and extracellular electron transfer were remarkably enriched. Possible mechanism for enhancement of p-CP degradation in bio-photodegradation system was proposed, in which photocatalytic H₂ and photoelectron transfer played an important role for enhancing p-CP mineralization by microbes. 3D semiconductor-microbe interfaces could maintain excellent performance for p-CP degradation after long-term operation, which provide a potential alternative for the enhanced treatment of wastewater containing p-CP.