Adsorption of antibiotic on chemically impregnated natural clay: Development, characterization, and process optimization

Herein, the valorisation of raw montmorillonite (Mt) via zinc impregnation was investigated to develop a high-performance nanomaterial (Zn–Mt) for the efficient removal of spiramycin from aqueous medium. Response surface methodology (RSM) was employed to evaluate the effects of key operational parameters, and the optimized conditions (pH 9.38; T 40 °C) resulted in a maximum adsorption capacity of 121 mg g^-1 for Zn–Mt, which was significantly higher than that of Mt. The adsorption kinetic data were well described by a pseudo-second order (PSO) model, while the adsorption equilibrium data were fitted to Dubinin-Radushkevich (D-R) isotherm model. Thermodynamic analysis affirmed that the adsorption process was exothermic and spontaneous. Comprehensive characterisation analysis using XRD, FTIR, DTA-TGA, BET, and SEM-EDX techniques confirmed successful zinc impregnation and notable physicochemical changes over the material's surface. The adsorption mechanism primarily involved hydrogen bonds, electrostatic interactions, and hydrophobic/π-alkyl effects. Desorption study using NaOH as eluent revealed over 90% spiramycin recovery, and Zn–Mt maintained its adsorption performance for over four consecutive regeneration cycles, demonstrating excellent reusability and structural stability. Overall, Zn–Mt emerges as a promising nanomaterial for the sustainable removal of pharmaceutical contaminants from water.