Adsorption of Pb(II) ion on mesoporous activated carbon prepared by ZnCl2 activation

概要

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The chemical activation with ZnCl2 was conducted to prepare mesoporous activated carbons (ACs) from bamboo chips (BC), and the optimization as well as mechanism of ZnCl2 activation was examined. The pore properties of the prepared ACs were evaluated through N2 adsorption/desorption isotherms. The results showed that both surface area and mesopore volume were significantly developed up to as much as 1900 m2/g and 1.6 cm3/g, respectively, by ZnCl2 activation at the impregnation ratio (ZnCl2/BC) of 9 g/g. The mesopore volume of the ACs could be controlled by varying the amount of ZnCl2 in the impregnation process. The development of porosity was observed around a 400–500 °C activation temperature, and was attributed to the expansion of the carbon microstructure by fusion and vaporization of ZnCl2. The increase in activation temperature to above 500 °C, however, caused a significant reduction of porosity for ACs. This was due to the rapid progression of organization of the graphite structure. Adsorption of Pb(II) ions revealed that it strongly depended on the number of total basic sites on the carbon surface rather than the mesopore volume, while the Pb(II) ion adsorption kinetics was much higher for ACs with a larger mesopore content.