Comparative study of naphthalene adsorption on activated carbon prepared by microwave-assisted synthesis from different typical coals in Xinjiang

Abstract

Coal-based activated carbons (CACs) prepared from anthracite (A) coal, bituminous (B) coal, and long flame (L) coal (i.e., ACAC, BCAC, and LCAC) from Xinjiang, China, using KOH as activating reagent, were investigated under various microwave radiation power levels. The results show that the adsorption capacity of the obtained activated carbons (prepared under the optimum power level) toward naphthalene follows the order: ACAC > BCAC > LCAC. In addition, the textural properties of the CACs were investigated by means of SEM and low-temperature N2 adsorption. The surface chemistry features of the CACs were investigated by XPS, FTIR spectroscopy and Boehm's titration method. ACAC has a higher surface area, pore volume, and zero point charge (pHPZC) than the BCAC and LCAC, while acidic oxygen functional group of the ACAC is lower than that of BCAC and LCAC. In addition, the adsorption of naphthalene from the aqueous solution on the CACs could be favorably described by the Freundlich isotherm. The adsorption kinetics fits very well to the pseudo-second-order model. Among the three coals, A-coal was the best material having low ash content and less than 10% volatile content, which is beneficial for the preparation of CAC using microwave -assisted synthesis for naphthalene adsorption.