Preparation and characterization of activated carbon from medlar seed by chemical activation with phosphoric acid and its application in uranium adsorption

The aim of this work was to synthesize a high-capacity adsorbent from medlar seeds by chemical activation using phosphoric acid. The confirmation of successful biomass activation was achieved through various characterizations, including SEM–EDS, FTIR, and nitrogen adsorption–desorption. The best parameters were found to be a temperature of 500 °C, a time of 60 min, and an impregnation ratio of 2:1. The specific surface area, average pore diameter, and total pore volume were identified as 1845.32 m²/g, 2.88 nm, and 0.896 cm³/g, respectively. The performance of the selected activated carbon was evaluated by using it for the sorption of uranium (VI) in a batch system. The maximum adsorption of 52.08 mg/g was obtained under optimum conditions: pH = 3.54, adsorbent dose of 2 g/L, adsorbate concentration of 100 mg/L, particle size between 0.125 and 0.20 mm, and contact time of 90 min. Until the fifth cycle of use, the prepared activated carbon showed excellent regeneration capacity (84.23%). The pseudo-second-order kinetic and the Langmuir isotherm were the best fitted, implying the monolayer chemical adsorption process. The adsorption process could be considered as spontaneous (ΔG° < 0) and exothermic process (− 84.601 kJ/mol).

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