Modification of Activated Carbon by Means of Microwave Heating and its Effects on the Pore Texture and Surface Chemistry

Abstract

Two kinds of typical activated carbons (coal based AC and coconut shell based AC) were modified in a flow of N₂ gas has been carried out using a microwave device operating at 2450 MHz and different input power, instead of a conventional furnace. The samples were analyzed by means of low temperature N₂ adsorption, elemental analysis and Boehm titration. The results show that microwave heating is an effective means of activated carbon modification. The temperature of activated carbon increases rapidly under microwave heating and then gradual increase to a quasi-stationary temperature. The pore texture of activated carbon changes slightly after microwave treatment and the two activated carbons still keep rich pore structure. The oxygen functional groups decompose and evolve with the form of CO and CO₂. This in turn gives rise to a significant decrease in oxygen content. These changes of oxygen contents increase as the microwave input power increases. During microwave treatment, a gradual decrease in the surface acidic functional groups is observed. More important, with the removal of the surface acidic groups, the number of the basic group increased gradually, the activated carbon with oxygen functional groups become basic properties material.