Humid-Air Regeneration\nof Microporous Adsorbents at\nAmbient Temperature for Cyclic Dynamic Adsorption of Volatile Organic\nCompounds: A Comparison with Thermal Regeneration

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