Experimental study on the manufacture of activated carbon in the presence of additives

Taixi anthracite was activated by steam in the presence of two kinds of additives, nitrate and potassium-containing compounds. The starting coal was ground to pass a 200 mesh sieve and mixed with additives and binder. The mixture was then kneaded, extruded, carbonized and activated. An orthogonal design was employed to analyze the effect of the ratio of the two additives, heating rate in carbonization, activation temperature and activation time on the microspore volumes of the resulting activated carbons. The optimum condition was found at the ratio of two additives, nitrate and potassium-containing compound, being 2∶1, heating rate 5℃/min, activation temperature 920℃ and soak time of 3.5h. The resulting activated carbons were tested using an Autosorb-1-MP with nitrogen at 77K. Their BET surface areas, total pore volumes, micropore volumes, micropore surface areas and pore size distributions were analyzed by the BET method, D-R equation and Density Function Theory (DFT). Pore size distributions of the activated carbons produced with 6w/% additives and without additives under the optimum conditions were analyzed by DFT. It is concluded that the use of 6w/% additives can effectively increase micropore volumes and total pore volumes, with the former increased from 0.1847mL/g to 0.3299mL/g and the latter increased from 0.2186mL/g to (0.5128mL/g.)