Comparison of Bet and Water Adsorption Techniques

Abstract

The effect of activated carbon surface area on the amount of fluid adsorbed is significant. Thus, the surface area of an adsorbent is an important factor. The use of the costly BET measurement method is the standard. However, water adsorption method was proposed as an alternate method. Nevertheless, results presented were for activated carbon prepared and surface areas reported were based on BET literature values. In this study, chemically activated carbons were produced from corn cobs by impregnation using 25 wt% CaCl₂ as activating agent. Surface area of the activated carbons was then determined using both BET technique and water adsorption techniques by determining the volume at monolayer coverage. Comparison between the results of surface areas obtained from the two techniques was performed. From the present experimental investigations, water adsorption technique showed a wide range of deviation with increase in surface area of adsorbent. It was established from the analyses that water adsorption technique approximate the BET technique reasonably well for surface areas below 200 m² g^-1, above this value results from water adsorption technique are not reliable.