Co single atoms anchored on straw biochar as an efficient peroxydisulfate activator for ultrafast removal of antibiotics

The removal efficiency of antibiotics decreases at low temperature, which is an urgent problem to be solved in cold regions. This study prepared a low-cost single atom catalyst (SAC) from straw biochar, which can rapidly degrade antibiotics at different temperatures by activating peroxydisulfate (PDS). Co SA/CN-900 + PDS system can degrade 100% of tetracycline hydrochloride (TCH, 10 mg/L) in 6 min. The high concentration of TCH (25 mg/L) was degraded by 96.3% in 10 min at 4 °C. The system was also tested in simulated wastewater and showed a good removal efficiency. TCH was primarily degraded by 1O2 and direct electron transfer pathway. Electrochemical experiments and density functional theory (DFT) calculations showed that CoN4 improved the electron transfer capacity of biochar and thus enhanced the oxidation capacity of Co SA/CN-900 + PDS complex. This work optimizes the application of agricultural waste biochar and provides a design strategy of efficient heterogenous Co SACs to degrade antibiotics in cold regions.