Cyanobacteria-derived biochar supported ZIF-8-derived ZnS–NC for superior peroxymonosulfate activation to remove 4-chlorophenol from wastewater†

Eutrophication of water bodies caused by cyanobacteria is a headache in water treatment nowadays, and the treatment of harvested cyanobacteria creates another difficult problem. Fortunately, cyanobacteria can produce biochar (BC) through pyrolysis, but the catalytic performance of BC is clearly unsatisfactory. Metal–organic frameworks, materials with multiple active centers, are naturally combined with BC for superior functional materials. In this study, ZnS–NC/BC was obtained by in situ growth of ZIF-8 on cyanobacteria-derived biochar and subsequent sulfur-doped pyrolysis. Characterization indicated that ZIF-8 was successfully uniformly loaded onto the BC substrate and transformed into ZnS-loaded N-doped graphitic carbon during the subsequent pyrolysis process. In the performance evaluation, ZnS–NC/BC-1 showed excellent peroxymonosulfate activation performance and 4-chlorophenol (4-CP) removal capability. Subsequently, it turned out that ¹O₂ dominated the degradation of 4-CP in the system. Furthermore, it was exciting to note that the system exhibited good resistance to various factors, including pH, inorganic anions, and humic acids. In addition, the removal of 4-CP and dissolved organic matter proceeded well even in natural water and sewage effluent. The degradation pathway of 4-CP was confirmed by density functional theory (DFT) and liquid chromatography-mass spectrometry (LC-MS) to be two, namely the degradation pathway and the polymerization pathway. In addition, the toxicity of the intermediates showed a general trend of detoxification, proving the toxicological feasibility. In conclusion, a feasible solution for the synergistic development of solid waste and water treatment was provided.