Catalytic degradation of tetracycline using peroxymonosulfate activated by cobalt and iron co-loaded pomelo peel biochar nanocomposite: Characterization, performance and reaction mechanism

Tetracycline (TC) is a refractory pollutant that widely exists in water environments. Therefore, effective TC treatment methods must be developed. In this work, a cobalt and iron coloaded pomelo peel biochar composite (Co-Fe@PPBC) was successfully synthesized and used to activate peroxymonosulfate (PMS) for TC removal. The crystal structure, surface morphology, pore structure, and elemental valence of the synthesized Co-Fe@PPBC catalyst were investigated by BET, SEM, XRD, FTIR, XPS, TGA, Raman, and VSM. The effects of Co-Fe@PPBC dosage, PMS concentration, initial pH, initial TC concentration, and coexisting anions on TC removal were studied. In comparison with the oxidation (13.6%) by PMS alone and adsorption (9.6%) by Co-Fe@PPBC alone, the removal efficiency of TC was increased to 86.2% in the Co-Fe@PPBC/PMS system, indicating that Co-Fe@PPBC can successfully activate PMS. Remarkably, the results of scavenging examination and EPR analysis demonstrated the synergistic effect of free radical and non-free radical pathways in TC degradation. The cycling test showed that Co-Fe@PPBC has favourable stability and recyclability during repeated activation processes of PMS. Finally, three possible TC degradation methods were presented through the analysis of eight intermediates. Overall, Co-Fe@PPBC could be an economic and high-efficiency catalyst for PMS activation to remove organic pollutants in wastewater.