Humid-Air Regeneration of Microporous Adsorbents at Ambient Temperature for Cyclic Dynamic Adsorption of Volatile Organic Compounds: A Comparison with Thermal Regeneration

Abstract

Recyclability is a crucial indicator for evaluating the adsorbent in terms of economic benefits and the superior cycle performance. In this study, ethanol, n-hexane, and n-heptane were selected as representative volatile organic compounds (VOCs), with hyper-cross-linked polymeric adsorbent (HPA) and activated carbon (AC) as adsorbents. Consecutive dynamic adsorption experiments were conducted on virgin and spent adsorbents using humid-air regeneration method with a relative humidity (RH) of 80% at ambient temperature (35 °C), compared with the thermal regeneration method at 110 °C. The results presented that, for both regeneration methods, the breakthrough adsorption capacities (q bre) of three VOCs on the spent adsorbent in the second run exhibited a clear reduction compared to the virgin adsorbent. For the third and fourth adsorption cycles, the q bre values were virtually unchanged compared with that of the second cycle. Both HPA and AC were rather stable in the consecutive adsorption/desorption process. For humid-air regeneration, HPA showed a better regeneration performance than AC. Moreover, on HPA, the reduction percentage (W bre) of the breakthrough adsorption capacity was as follows: n-hexane > ethanol. However, on AC, the order of W bre was reversed. In the case of thermal regeneration, AC had a superior regeneration performance compared to HPA, and the value of W bre for both adsorbents was as follows: ethanol > n-heptane > n-hexane. Notably, at the same condition, humid-air regeneration at ambient temperature had rather better efficiency and technoeconomic advantage for multiple adsorption/desorption cycles than thermal regeneration.