The competing role of moisture in adsorption of gaseous benzene on microporous carbon

Abstract

The effects of moisture on adsorption of gaseous benzene have been investigated using microporous activated carbon (AC). Here, the performance metrics of an AC bed are explored in terms of the interplay between benzene concentrations (1–20 Pa) and relative humidity (RH, 0–100%). At lower benzene levels (<10 Pa), the adsorption capacity of AC bed was affected sensitively by water vapor with the performance reduction by 27–65% at 100% RH (e.g., relative to 0% RH). In contrast, the negative effect of water on AC performance was not so evident at higher benzene levels (~20 Pa) with only less than 5.3% decrease in the adsorption capacity. A test on the combinatory effects of temperature (25, 40, and 60 °C) and humudity (0 and 100% RH) confirms the relative dominance of temperature over moisture conditions in lowering AC performance. The isotherm analysis of benzene indicates complex fitting results of microporous AC across varying RH levels. The kinetic analysis further demonstrates that the physical nature of benzene is best explained by the pseudo-first order fitting. The test of temperature-swing cycles between adsorption–desorption clarifies the slight decreases in the adsorption capacity (reduction of 11.9% at 0% RH and 3.4% at 50% RH) at lower RH levels, although there is a prominent reduction (35.5%) at the saturated RH. As a whole, the commercial AC product is verified as an excellent adsorbent for purifying the atmosphere from gaseous aromatic pollutants like benzene under dynamically varying environmental conditions (e.g., in the presence of competing component like water vapor at different temperature conditions).