Adsorption of cephalexin onto activated carbons from Albizia lebbeck seed pods by microwave-induced KOH and K2CO3 activations

Microwave technique has been adopted for preparation of two activated carbons from agricultural wastes, Albizia lebbeck seed pods, by KOH and K2CO3 activation. Adsorption mechanisms of a first generation cephalosporin antibiotic, cephalexin (CFX), onto both carbons namely KAC and KCAC have been compared. The yield and surface area of KAC were 22.48% and 1824.88 m2/g compared to 26.19% and 1676.61 m2/g for KCAC. The analysis of pore structures of prepared carbons showed that KOH activation exhibited higher mesopores content than K2CO3 activating. The experimental isotherm data for adsorption of CFX onto both carbons were analyzed by Langmuir, Freundlich and Temkin isotherms. Langmuir isotherm was the best model giving maximum adsorption capacities of 137.02 and 118.08 mg/g on KAC and KCAC, respectively. The kinetic data were well represented by the pseudo-second order model for adsorption onto both carbons. Thermodynamics analysis showed an endothermic CFX adsorption on KAC compared to an exothermic adsorption on KCAC under examined conditions.

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► Albizia lebbeck seed pods were used as precursors for activated carbons.
► KOH and K2CO3 microwave activations were adopted for preparation.
► KOH activation exhibited carbon of a higher capacity for cephalexin.
► K2CO3 activation gave carbon with a higher portion of mesopores.
► Sorption isotherms, kinetics and thermodynamics were evaluated.