Maize Cob-Based Adsorbent for Efficient Removal of Amoxicillin from Aqueous Systems: Isotherm Modeling, Kinetics, and Desorption Studies

Abstract

Antibiotic pollution has emerged as a major environmental concern due to the widespread use of antibiotics, their persistence in aquatic systems, and their adverse effects on ecosystems and human health. Consequently, the development of efficient and sustainable technologies for antibiotic removal from water has become increasingly important. This study investigated the potential of raw maize cob, an abundant agricultural waste, as a low-cost adsorbent for removing amoxicillin from aqueous solutions. Amoxicillin concentrations were determined using a validated UV–Visible spectrophotometric method with satisfactory linearity, sensitivity, accuracy, and precision. FTIR and SEM analyses confirmed the involvement of surface functional groups and morphological changes during adsorption, while BET analysis revealed reductions in surface area and pore volume after adsorption. Optimum adsorption was achieved at an adsorbent dosage of 0.1 g (50.92 mg g^-1), pH 6 (31.34 mg g^-1), initial concentration of 40 mg L⁻¹ (33.80 mg g^-1) and a contact time of 140 min (81.42 mg g-1). The adsorption kinetics followed the pseudo-second-order model (R² = 0.987), whereas equilibrium data were best described by the Langmuir isotherm model (R² = 0.913), with a maximum adsorption capacity of 46.35 mg g⁻¹. Regeneration studies showed adsorption and desorption efficiencies exceeding 96% after three cycles. The possible adsorption process was governed by hydrogen bonding, electrostatic attraction, and surface complexation, demonstrating the potential of maize cob as a sustainable adsorbent for amoxicillin-contaminated water.