Preparation of Activated Carbons from Bituminous Coals with Zinc Chloride Activation

Activated carbons were prepared by chemical activation from two Australian bituminous coals in this study. The preparation process consisted of zinc chloride impregnation followed by carbonization in nitrogen. The carbonization temperature ranges from 400 to 700°C. Experimental results reveal that an acid-washing process following the carbonization with ZnCl₂ is necessary for preparing high-porosity carbons. Surface area, pore volume, and average pore diameter of the resulting carbons increase with the carbonization temperature to a maximum at 500°C and then begin to decrease. The maximum values of surface area and pore volume are larger for the carbon prepared from the coal with a lower O/C atomic ratio, while earlier findings from physical activation with CO₂ have shown an opposite trend. An increase in particle size of the coal precursor leads to a reduction in porosity of the resulting carbons. The duration of the carbonization period affects the porosity of the resulting carbons, and the influence varies with the activation temperature.