Single-atom copper anchored on algal-based carbon induce peroxydisulfate activation for tetracycline degradation: DFT calculation and toxicity evaluation

Single-atom catalysts have wide application prospects in peroxydisulfate (PDS)-based advanced oxidation process to degrade organic pollutants, but its catalytic performance is limited due to its cost, Metal-N coordination number, and single-atom loading amount. Herein, a novel nitrogen doped algal-based carbon confined single-atom copper catalyst (Cu–N/C-SAC(S)) was synthesized using molten salt assisted pyrolysis and coupling with PDS to degrade tetracycline (TC). AC-HAADF-STEM and XAFS analysis proved that single atom Cu was loaded (Content 1.9 %) successfully and coordinated with two N and two C. XPS and XANES spectra analysis suggested that Cu atoms mainly existed in a positive divalent state in Cu–N/C-SAC(S). When the catalyst dosage of Cu–N/C-SAC(S) was 0.1 g/L, TC was almost completely removed. Moreover, Cu–N/C-SAC(S) had a broad pH adaptation range and strong ability against interference. Singlet oxygen (1O2), superoxide radicals (•O2−), and electron transfer had an important contribution for TC removal. DFT calculations confirmed that the activation process of Cu–N/C-SAC(S) producing SO4•− was easier than the nitrogen doped blue-green algal-based carbon (N-BGAC). In addition, Cu–N/C-SAC(S) possessed good recyclability and stability. The main degradation pathways of TC were analyzed, and the toxicity of the intermediates was calculated. This study provides a new solution strategy for the resource utilization of waste biomass, and provides technical support and theoretical guidance for the efficient application of single-atom catalysts in organic wastewater.