Surface functionalized magnetic activated carbon for efficient p-nitrophenol removal: Surface interactions, adsorption mechanism, and reusability

This study reports the fabrication and surface engineering of Pistacia vera shell-derived magnetic activated carbon (PSMAC) via H 3 PO 4 activation followed by Fe 3 O 4 incorporation, and its application for interface-driven removal of PNP from aqueous systems. The prepared adsorbent exhibited a high specific surface area (1099.2 m 2 g −1 ) with a predominantly microporous structure and well-dispersed magnetic phases, enabling efficient separation after treatment. Batch adsorption experiments demonstrated strong pH dependence, with optimum performance at pH 2, achieving a maximum monolayer adsorption potential of 111.15 mg g −1 . The equilibrium dataset satisfactorily fitted with the Freundlich isotherm model, signifying heterogeneous multilayer adsorption, while the kinetic results followed pseudo-second order kinetics, demonstrating that the uptake process was controlled by surface-controlled mechanisms. The thermodynamic study confirmed that the adsorption is spontaneous and exothermic. Spectroscopic and microscopic characterisations revealed that p -nitrophenol (PNP) removal is regulated by multiple surface/interface interactions including π-π stacking, hydrogen bonding, hydrophobic effects, electron donor-acceptor interactions, pore diffusion and weak surface complexation with FeO sites. Regeneration studies showed that PSMAC retained substantial adsorption capacity over five cycles, and real water matrix experiments confirmed its practical applicability under complex conditions. PSMAC presents a sustainable, efficient, and reusable adsorbent for phenolic contaminant remediation.