Application and Characterization of Fruit Peel-Based Natural Adsorbents for Diclofenac and Amoxicillin Removal from Aqueous Solutions: A “Waste-to-Resource” Approach

Pharmaceutical-contaminated wastewater from medical facilities and households can cause ecological damage. In this study, 100% natural fruit peels, namely lime (LP), orange (OP), kiwi (KP), fig (FP), and pomegranate (PP) peels, were investigated as low-cost adsorbents for the removal of diclofenac (DCF), a non-steroidal anti-inflammatory drug (NSAID), and amoxicillin (AMX), an antibiotic, from aqueous solution. The goal of this study was to use food waste as a source for wastewater treatment. According to the results, natural fruit peels were effective for DCF removal (C0 = 100 mg/L), with KP achieving a high removal efficiency (98.9%, 345.18 mg/g) at pH 3.0). The most promising materials (OP, KP, and FP) were further modified using MgO suspension followed by alkaline treatment with NaOH (OP-Mg, KP-Mg, and FP-Mg), resulting in enhanced performance for AMX removal (65.1%, 286.61 mg/g at pH 3.0, C0 = 50 mg/L). The maximum short-term uptake capacity was reached within 15 min, and kinetic and isotherm models were applied to describe the adsorption data. The Langmuir expression gave the better description of the concentration dependence for both pharmaceuticals, at equilibrium for DCF and at a fixed contact time of 15 min for AMX. SEM, FTIR and XRD characterization techniques provided information on the adsorption mechanisms, as well as confirming the successful modification with Μg. In conclusion, the results demonstrate that natural fruit peels were effective in the removal of pharmaceuticals and at the same time offer potential cost and environmental advantages through waste valorization and relatively simple preparation, supporting the principles of the circular economy, through the utilization of food waste as sustainable materials for water treatment.