In-situ toxic mechanisms of the antibiotic intermediates in the biogas slurry based on the constructed visible light photocatalytic-selfcleaning system of Cu@Cu2O/PF/BCs

A photocatalytic superhydrophobic reaction interface of Cu@Cu 2 O/PF/BC suitable for the special environment of biogas slurry was ingeniously constructed by combining the in-situ synthesis and spray anchoring method, and the in-situ degradation and removal of antibiotics in the biogas slurry had been achieved. The degradation rate of oxytetracycline (OTC) in the biogas slurry by the Cu@Cu 2 O/PF/BC could reach 93.6%. By combining high-resolution mass spectrometry and toxicological simulation, the quantitative structure-activity relationship (QSAR) and biological toxicity evolution process of the OTC and its degradation products were discovered. The results indicated that about half of the degradation intermediates had increased acute toxicity compared to the parent OTC. The dealkylation of dimethylamino group, amino conversion of amide group, oxidation of alcohol hydroxyl group, removal of hydroxyl group and decarbonylation reaction on the D ring were the five key reaction pathways that triggered the deconstruction of OTC by the attacks of ·O 2 − and ·OH. The formation and accumulation of the hub toxic products directly affected the direction and toxicity evolution trend of the entire degradation pathway, and provided the key regulatory nodes for blocking the highly toxic intermediates. • The Cu@Cu 2 O/PF/BCs achieved efficient photocatalysis and interface self-cleaning. • The ·O 2 − and ·OH triggered the five initial reaction pathways of OTC. • The biological toxicities of half products were significantly higher than that of OTC. • The toxicity evolution trends were dominated by the intermediates with control hub.