Amoxicillin adsorption on microwave prepared activated carbon from Arundo donax Linn: Isotherms, kinetics, and thermodynamics studies

Microwave-assisted KOH activation of renewable biomass Arundo donax Linn was adopted for preparation of activated carbon (KAC) with high capacity for amoxicillin antibiotic (AMX). The characteristics of KAC were examined by proximate and pore structure analyses, scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR). The ash and moisture contents of KAC were 5.5 and 0.5% compared to 2.2 and 2.1% for raw biomass. The BET surface area and total pore volume were identified to be 1065.3 m(3)/g and 0.643 cm(2)/g, respectively. The best preparation conditions in terms of KAC yield and AMX uptake were reported as 10 min radiation time, 620 W radiation power and 2 g/g impregnation ratio resulted in 9.1% yield and 196.9 mg/g AMX uptake. Experimental equilibrium data for AMX adsorption were analyzed by Langmuir, Freundlich, and Sips isotherms. The results showed that the best fitting was achieved by Sips isotherm with high adsorption capacity of 345.4 mg/g on KAC compared to 75.8 mg/g on precursor. Also, kinetic data were correlated by pseudo-first order, pseudo-second order, and intra-particle diffusion models with well-fitting to pseudo-second order model. Thermodynamic analysis showed that adsorption enthalpy of AMX was 17.7 kJ/mol which revealed endothermic and physisorptive nature under examined conditions. (C) 2015 Elsevier Ltd. All rights reserved.