Avocado Seed‐Derived Activated Carbon for the Bioremediation of Uranium(VI) and Thorium(IV): Process Optimization via Response‐Surface Methodology

ABSTRACT Activated carbon derived from avocado seeds (ASAC) was synthesized by phosphoric acid activation and evaluated for U(VI) and Th(IV) removal from acidic water. Batch tests interpreted with response‐surface methodology identified initial pH and metal concentration as the dominant variables. Under optimal conditions (pH 3.0, 50 mg/L, 25°C), Langmuir fits yielded monolayer capacities of 49.5 mg/g for U(VI) and 69.4 mg/g for Th(IV). More than 90% of uptake occurred within 5 min under the previous conditions, and the time‐profiles were well described by a pseudo‐second‐order model (PSO). Isotherm and thermodynamic parameters ( ΔG ° < 0, ΔH ° < 0) indicate spontaneous, exothermic physisorption. SEM and XRD confirmed a meso‐/microporous carbon rich in oxygenated sites that promote ion exchange and surface complexation. Transforming an abundant agricultural residue into an efficient radionuclide sorbent offers a cost‐effective option for treating mining and nuclear effluents while valorizing waste biomass.