Removal of paracetamol using novel adsorbents: Optimization, isotherm, kinetic, and thermodynamic studies

The increasing global consumption of paracetamol (PCM) has led to its frequent detection in pharmaceutical effluents, posing serious environmental and public health risks. This study explores the development of eco-friendly and sustainable adsorbents. Coconut shell–based alkali-activated carbon (CSAAC) and its magnetic nanocomposite (Fe₃O₄NPs-CSAAC) were synthesized for efficient PCM removal from aqueous media. Magnetic iron oxide nanoparticles (Fe₃O₄NPs) were synthesized via a green route using black tea extract as a reducing agent and subsequently impregnated onto CSAAC to form Fe₃O₄NPs-CSAAC. Characterization analyses confirmed enhanced surface and textural properties, with BET surface area, total pore volume, and average pore diameter of 990.35 m2/g, 0.554 cm3/g, and 5.44 nm, respectively. Process optimization using the Definitive Screening Design identified pH, temperature, contact time, adsorbent dose, and initial PCM concentration as key parameters. Under optimal conditions, PCM removal efficiencies of 90.01% (Fe₃O₄NPs-CSAAC) and 76.42% (CSAAC) were attained. Thus, the modified adsorbent (Fe3O4NPs-CSAAC) achieved 13.59% higher removal than its unmodified activated carbon (CSAAC). Adsorption data fitted well to the Langmuir and the Freundlich isotherms for CSAAC and Fe₃O₄NPs-CSAAC, while kinetics followed the pseudo-second-order model. Thermodynamic analysis indicated spontaneous and endothermic adsorption. Both adsorbents demonstrated excellent reusability over four regeneration cycles, underscoring their potential for sustainable wastewater remediation.