Construction of biochar supported single cobalt atom catalysts from coffee grounds on peroxymonosulfate activation for sulfamethoxazole degradation

Designing low-priced and highly efficient single atom catalysts used on organic pollutant degradation in advanced oxidation processes (AOPs) has always been one of the research hostpots in this field. Hence, waste biomass of coffee grounds was used as raw carbon materials to prepare single cobalt atom catalysts (SA-Co₁₂-BC) for peroxymonosulfate (PMS) activation on sulfamethoxazole (SMX) removal. In SA-Co₁₂-BC/PMS system, 10 mg/L SMX could be removed almost 100 % in 30 min at low doses of catalyst (0.1 g/L) and oxidant (0.5 mM). The experiments exposed that ¹O₂ and electron transfer pathway were the main mechanism for SMX degradation. Benefiting from that, this system exhibited a wide pH adaptation (3.1 ∼ 11) and high resistance to inorganic anions in various water environment. A possible degradation pathway for SMX was proposed based on mass spectrometry and density functional theory (DFT) calculation results analysis, and T.E.S.T. software evaluation speculated that the toxicity of intermediate products gradually decreased with degradation. More importantly, SA-Co₁₂-BC could maintain above 94 % removal of SMX for 10 h in continuous flow experiments. Overall, this work provides an effective strategy for biochar-based single atom catalysts design and application in AOPs for organic pollutant removal.