Efficient Degradation of 4-Chlorophenol by Peroxymonosulfate Activation over N-Doped Gasification Residue Based Porous Carbon: Synergistic Adsorption-Catalysis via Multiple Active Sites

Abstract This study aimed to develop an N-doped porous carbon catalyst with a three-dimensional interconnected well-developed pore structure and balanced N functionality distribution using coal gasification fine slag as a precursor. This work focused on elucidating the role of N doping in promoting the adsorption-catalysis synergy during peroxymonosulfate (PMS) activation for 4-chlorophenol degradation. Compared with raw gasification slag, the constructed 900-N-PSRC/PMS system exhibited significantly enhanced degradation performance, achieving 98% 4-CP removal within 30 min and approximately 75% mineralization, along with strong adaptability under harsh conditions (including high inorganic anions concentrations, broad pH range, and diverse water matrices). Mechanistic studies revealed that the reaction was dominated by a single oxygen (1O2)-mediated nonradical pathway, endowing the system with high selectivity toward electron-rich organic contaminants. Correlation analysis and density functional theory calculations confirmed that pyridinic N, pyrrolic N and the well-developed porous structure facilitated 4-CP enrichment and mass transfer, while graphitic N and C═O groups served as key activity sites for PMS activation, with functional differentiation of adsorption and catalytic sites enhancing overall treatment efficiency. This work provides a viable strategy for high-value utilization of coal gasification slag and mechanistic insights for designing N-doped carbon catalysts toward the control of recalcitrant organic pollutants.