Hierarchically porous N, S co-doped green bean biochar for efficient tetracycline degradation via peroxymonosulfate selective activation: Synergistic mechanism of adsorption and non-radical oxidation

Non-radical oxidation pathways including singlet oxygen ( 1 O 2 ) and electron transfer process (ETP) exhibit high oxidant utilization and strong resistance to substrate interference, yet their efficiency in antibiotic removal depends on the adsorption performance and the peroxymonosulfate (PMS) activation ability of the catalyst. Herein, hierarchically meso-macroporous N, S co-doped biochar (NSBC-2) is fabricated from green beans and thiourea via a simple carbonization strategy. The doping of N and S effectively increases active sites (pyrrolic N, and thiophene S) of NSBC-2, thereby facilitating PMS activation to produce 1 O 2 and ETP, which play dominant roles in NSBC-2-activated PMS system for tetracycline (TC) degradation. In addition, the formation of the hierarchically porous structure facilitates the rapid adsorption and enrichment of TC molecules on NSBC-2 surface, shortening the diffusion distance between the pollutant and the non-radical species. By virtue of non-radical-dominated PMS activation and superior adsorption ability, the NSBC-2-activated PMS system exhibits an excellent adsorption efficiency (56.1%) and degradation efficiency (91.1%) of TC within 90 min, with strong resistance to pH value (3−11), inorganic anions and natural organic matter. Moreover, NSBC-2 maintains stable TC degradation efficiency after 5 cycles as well as in various natural water. This work presents a novel adsorption-catalytic bifunctional catalyst for efficient antibiotic removal. • Hierarchically meso-macroporous N, S co-doped biochar (NSBC-2) is synthesized. • This unique design enables PMS activation to preferentially generate 1 O 2 and ETP. • TC adsorption on NSBC-2 is a chemisorption-controlled monolayer process. • Synergistic adsorption-non-radical oxidation mechanism for TC removal is proposed.