Study of the influence of some factors on the preparation of activated carbon from walnut cake using the fractional factorial design

In this work, different factors which interfere in the preparation of activated carbon from walnut cake using phosphoric acid activation were studied in order to determine the optimal conditions. The effects of activation temperature (400-500 degrees C), time of stay (30-60 min), impregnation ratio (0.5-2), heating rate (10-20 degrees C/min) and the atmosphere (without N-2-with N-2) on the yield and on the adsorption of methylene blue and iodine were established. Due to the existence of a number of factors, a two-level fractional factorial design 2(5-1) was used to reduce the number of experiments and also to study the main effects and the first order interactions of various factors. The results have shown that the most influential factors on the yield, the methylene blue adsorption and iodine adsorption are activation temperature, impregnation ratio and atmosphere. To obtain adequate activated carbon, one should work at high temperature of activation with a high impregnation ratio in the domains of interest and under air. The new activated carbon has adsorbed methylene blue from 70.39 to 243.04 mg g-1 and iodine from 343.79 to 645.23 mg g(-1) more than some activated carbon prepared from other byproducts. These results demonstrated that the walnut cake is a suitable precursor for the production of activated carbon with high mesoporosity.