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

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 (qbre) 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 qbre 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 (Wbre) of the breakthrough adsorption capacity was as follows: n-hexane > ethanol. However, on AC, the order of Wbre was reversed. In the case of thermal regeneration, AC had a superior regeneration performance compared to HPA, and the value of Wbre 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.