Reduction of adsorption capacity of coconut shell activated carbon for organic vapors due to moisture contents

Abstract

In occupational hygiene, activated carbon produced from coconut shell is a common adsorbent material for harmful substances including organic vapors due to its outstanding adsorption capacity and cost advantage. However, moisture adsorption of the carbon generally decreases the adsorption capacity for organic vapors. In a previous report, we prepared several coconut shell activated carbons which had been preconditioned by equilibration with moisture at different relative humidities and measured the breakthrough times for 6 kinds of organic vapor, in order to clarify the effect of preliminary moisture content in activated carbon on the adsorption capacity in detail. We found that the relative percent weight increase due to moisture adsorption of the carbon specimen had a quantitative effect, reducing the breakthrough time. In this report, we carried out further measurements of the effect of moisture content on the adsorption of 13 kinds of organic vapor, and investigated the relationship between moisture adsorption and the reduction of the breakthrough time of activated carbon specimens. We also applied the data to the Wood's breakthrough time estimation model which is an extension of the Wheeler-Jonas equation.