Chitosan-templated 3D spherical network construction from cellulosic waste residues for sustainable antibiotic wastewater purification

The sustainable management of solid wastes and the development of cost-effective catalysts for wastewater remediation are two pressing challenges in environmental engineering. Herein, cellulose-rich waste paper pulp (WPP) and iron-containing warm-paste residues (WPR) were synergistically upcycled into a three-dimensional (3D) hierarchical porous composite through chitosan-assisted crosslinking followed by carbonization. By integrating biomass-derived carbon frameworks with iron-rich solid waste, a robust spherical catalyst with tailored pore architecture and highly dispersed active sites was successfully fabricated. The optimized Fe0.4@CS0.7-6 N-700 catalyst exhibited outstanding performance toward peroxymonosulfate (PMS) activation for sulfamethoxazole (SMX) degradation. The incorporation of WPP effectively suppressed the aggregation of iron species, promoted the formation of a conductive carbon network, enhanced mass transfer, and exposed abundant accessible catalytic sites. Mechanistic investigations demonstrated that Fe nanoparticles and graphitic-N species functioned synergistically as dual catalytic centers, facilitating PMS activation through both radical and non-radical pathways. Density functional theory calculations further revealed enhanced PMS adsorption and accelerated interfacial electron transfer on the Fe N coupled active sites, accounting for the superior catalytic activity. This work establishes a structure–activity relationship for waste-derived porous catalysts and provides a sustainable strategy for simultaneously realizing solid-waste valorization and efficient removal of emerging organic contaminants.