From waste to treasure: synthesis of Ag3PO4/TiO2/r-SiC composite photocatalysts with efficient photocatalytic performance using waste photovoltaic silicon wafers

The conversion of low-value waste into high-value-added photocatalysts for pollution removal is considered a promising approach for waste utilization. In this work, regenerated SiC (r-SiC) nanowires were synthesized using waste photovoltaic silicon wafers through a mechanochemical-carbothermal reduction method. The prepared filamentary structure of r-SiC nanowires as a substrate for an Ag3PO4/TiO2/r-SiC (APO/TIO/r-SiC) ternary photocatalyst was prepared by immobilizing TiO2 and Ag3PO4 on r-SiC nanowires. The 30%APO/TIO/r-SiC (loaded with 30wt%Ag3PO4) achieved more than 90% degradation rate for six organic dyes, and 80% for tetracycline (TC) within 15min, respectively. The loading of TiO2 and Ag3PO4 improved the adsorption of molecular oxygen in the aqueous environment, which facilitated the generation of reactive oxygen species and enhanced the photocatalytic performance of 30%APO/TIO/r-SiC. The Z and II dual-scheme electron transfer mechanism for 30%APO/TIO/r-SiC was demonstrated to promote effectively carrier separation. Three potential pathways of RhB degradation were proposed, and the disruption of the conjugated structure (chromophore) was the main cause of RhB degradation. The radical quenching experiments revealed that the degradation process was more significantly influenced by •O2- and •OH than h+. The research proposed a promising 'win-win' treatment approach for waste photovoltaic wafers and delved into the photocatalytic performance and enhancement mechanism of SiC-based composite catalysts.