Highly efficient and sustainable removal of cyclophosphamide with activated carbon produced from peanut shells: chemical adsorption mechanism

This study investigates the feasibility of activated carbon produced from peanut shells via chemical activation for the removal of cyclophosphamide (CP) from aqueous solutions. CP, a cytotoxic antineoplastic drug, is frequently detected in hospital wastewater at concentrations ranging from ng/L to µg/L. However, it cannot be effectively removed by conventional biological and physical–chemical treatment technologies. Peanut shells were converted into activated carbon by KOH activation. The resulting adsorbent exhibited a surface area of 912 m2/g and a total pore volume of 0.58 cm3/g by BET analysis. SEM images revealed an irregular and highly macro- and mesogogenic morphology. In batch adsorption experiments, CP removal exceeding 98.5% was achieved with an adsorbent dose of 0.4 g/L, a neutral pH, an initial concentration of ≤ 40 mg/L, and a contact time of 60 min. Equilibrium data showed excellent fit to the Langmuir isotherm model (R2 = 0.9999), while kinetic data showed excellent fit to the pseudo-second-order model (R2 = 0.9998). Thermodynamic analyses revealed that the process was endothermic (ΔH° =  + 59.26 kJ/mol) and spontaneous (ΔG° < 0). Consequently, peanut shell-derived activated carbon has proven to be a cost-effective, environmentally friendly, and highly efficient adsorbent and a strong alternative for the treatment of pharmaceutical wastewater containing CP.