Persulfate assisted photocatalytic degradation activity and mechanism of tetracycline by Cu enriched reed hydrothermal carbonization carbon: Synergistic effect and DFT calculation

Heavy metal-enriched reeds can cause secondary pollution if not handled properly, and in addition, they can enter the organisms through the food chain, which can seriously harm the ecosystem. In this study, reed straw was first converted into hydrothermal carbonization carbon (HTCC) with adsorption and photocatalytic properties by acid etching and hydrothermal carbonization, then the prepared HTCC was used for adsorption of heavy metal Cu wastewater to obtain Cu/HTCC, and finally the photocatalytic degradation of tetracycline (TC) was enhanced with the assistance of persulfate. The results showed that the enrichment of Cu did not change the structural properties of HTCC, while the Cu on the surface of Cu/HTCC formed bridging interactions with TC in solution, which improved the TC degradation by Cu/HTCC+light+PS. The degradation efficiencies of Cu/HTCC+light+PS for TC were and 99%, which were 2.5 and 4 times higher than those of Cu/HTCC+light (40%) and HTCC+light+PS (25%), respectively. The Cu/HTCC+light+PS system degraded TC well over a wide pH range and in the presence of common anions (＞80%). Density functional theory (DFT) calculations and photoelectrochemical tests showed that Cu/HTCC has a strong charge separation and charge transfer ability during the photocatalytic process, where electrons preferentially migrate from the polyfuranic chain to Cu. The degradation mechanism and degradation pathway of TC by the Cu/HTCC+light+PS system were proposed by burst experiment, EPR and HPLC-MS tests, and the toxicity of the degradation products was analyzed by using the ECOSAR procedure. This study provides a new perspective for the preparation of biomass derived green photocatalysts and shows its application in environmental remediation. [Display omitted] •TC was almost completely removed when the Cu/HTCC dosage was 0.5 g/L(1 M PS).•Cu/HTCC has a wide pH adaptation range and strong anti-interference ability.•Cu forms a bridging mode with TC in solution and improves TC degradation.•The main active substances in the degradation process were·SO4− and ∙OH.•Photocatalysis and persulfate synergistically promote TC degradation