Equilibrium and hysteresis formation of water vapor adsorption on microporous adsorbents: Effect of adsorbent properties and temperature

ABSTRACT

Water vapor has been one of the vital problems in purification of volatile organic compounds. In this study, the adsorption-desorption equilibrium of water vapor were conducted at 298, 308, 318, and 328 K on three adsorbents: hypercrosslinked polymeric adsorbents (HPA), activated carbon fiber (ACF) and granular activated carbon (GAC). The obtained isotherms were type V and the adsorption capacity at the same condition was: GAC>ACF>HPA. cluster formation induced micropore filling (CIMF) model was adopted to fit the adsorption isotherms and the fitting parameters showed that adsorption capacities of water vapor on micropores and functional groups had a negative logarithmic linear relationship with temperature. The existence of functional groups could weaken the negative influence of temperature on the water adsorption performance, while the influence of temperature had negligible relationship with microporous volume. The hysteresis loops at different temperatures on three adsorbents had similar shape, the size of which were also: GAC>ACF>HPA. They mainly occurred in micropore adsorption, but their size had positive relationships with both functional groups and microporous volume. The hysteresis became smaller along with the increase of temperature, closely related with the stability of water clusters. In conclusion, temperature, functional groups and porous structure played crucial roles for water vapor adsorption and the formation of hysteresis.

Implications: Water vapor is one of the vital influence for VOCs recovery, so studying the adsorption mechanism of water vapor is important to weaken its negative effect. Adsorption capacities of water vapor on both micropores and functional groups had a negative logarithmic linear relationship with temperature. The existence of functional groups could weaken the negative influence of temperature on the water adsorption performance, while the influence of temperature had negligible relationship with microporous volume. The hysteresis loops on three adsorbents mainly occurred in micropore adsorption, but their size had positive relationships with both functional groups and microporous volume.

Acknowledgment

This research was financially funded by the National Natural Science of China (Grant No. 51808485), Department of Education, Shanxi Province (Grant No. 2019L0853), Department of Science and Technology, Shanxi Province (Grant No. 201901D211459) and Research Project Supported by Shanxi Scholarship Council of China (Grant No. 2021-150).

Data availability statement

The data supporting the findings of this study are available within the paper and its supporting information.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supporting information

CIMF parameters were listed in Table S1. Fig. S1 displayed the relationship between the water vapor adsorption capacity on functional groups and the concentrations of different functional groups on adsorbents. Adsorption and desorption isotherms of water vapor respectively on micropore and functional groups on three adsorbents were presented in Fig. S2-S4.

Supplemental data

Supplemental data for this paper can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the Research Project Supported by Shanxi Scholarship Council of China (2021-150); Department of Science and Technology, Shanxi Province (201901D211459); Department of Education, Shanxi Province (2019L0853); National Natural Science of China (51808485).

Notes on contributors

Lijuan Jia

Lijuan Jia is an associate professor in Department of Applied Chemistry, Yuncheng University, Yuncheng, China.

Ben Niu

Ben Niu is a manager and experimenter in the Department of Logistics, Yuncheng University, Yuncheng, China.

Xiaoxia Jing

Xiaoxia Jing is an associate professor in Department of Applied Chemistry, Yuncheng University, Yuncheng, China.

Yangfang Wu

Yangfang Wu is a lecturer in Department of Applied Chemistry, Yuncheng University, Yuncheng, China.