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

Figures & data

Table 1. Selected properties of HPA, ACF and GAC (Jia, Yao, and Ma 2017)

Adsorbents	HPA	ACF	GAC
Pore structure
SBET(m^2/g)	944.4	1139.3	2089.3
Vmicro(mL/g)	0.43	0.45	0.84
Vmeso(mL/g)	0.36	0.03	0.78
Average pore diameter(nm)	2.73	1.68	2.70
Surface functional groups
–OH (mmol/g)	0.207	0.757	0.984
–C = O (mmol/g)	0.124	0.178	0.196
–COOH (mmol/g)	0.032	nd	0.517
–COOR (mmol/g)	0.374	nd	0.004
Total acidic (mmol/g)	0.737	0.935	1.701

Figure 1. Adsorption equilibrium and kinetics schematic diagram of water vapor (a) high purity nitrogen, (b) mass flow meter, (c) thermostatic water bath, (d) bubble bottle, (e) buffer bottle, (f) thermal gravimetric analyzer, (g) bypass (h) offgas.

Figure 2. Adsorption-desorption isotherms (a,b,c) of water vapor on HPA, ACF and GAC at four temperatures and the zoomed-in view at 318 K and 328 K(d,e,f).

Table 2. CIMF fitting results of water vapor adsorption on HPA, ACF and GAC

Adsorbents	Parameters	Adsorption				Desorption
		298 K	308 K	318 K	328 K	298 K	308 K	318 K	328 K
HPA	Cus	350.9	78.07	27.18	10.49	350.1	89.6	39.2	14.21
	S0	5.628	2.085	0.172	0.069	2.863	1.088	0.512	0.084
ACF	Cus	370.3	100.9	32.50	13.11	370.4	103.0	52.79	20.10
	S0	10.68	3.827	1.509	0.549	9.593	8.004	4.238	1.495
GAC	Cus	1100	423.8	107.8	39.58	1117	425.4	119.9	44.51
	S0	13.57	8.694	4.436	1.565	13.73	9.216	5.813	2.270

Figure 3. Relationship between the adsorption capacity of water vapor on acidic groups with (a) the concentration of total acidic groups and (b) acidic groups except for –COOR.

Figure 4. Relationship between the adsorption capacity of water vapor on micropores and the microporous volume of adsorbents.

Figure 5. Variation of S₀ and C_μs with temperature for water vapor adsorption on HPA, ACF and GAC at four temperatures (298, 308, 318, and 328 K).

Figure 6. Adsorption and desorption isotherms of water vapor on micropore and functional groups respectively at 298K (A: HPA-a/b, B:HPA-a, C: ACF-a/b, D:ACF-a, E: GAC-a/b, F:GAC-a; a: functional groups, b: micropores).

Figure 7. Effect of total (a)acidic groups concentration and (b) microporous volume on hysteresis loop size.

Figure 8. Hysteresis loop size of water vapor on three adsorbents at different temperatures.

Jia, L., X. Yao, and J. Ma. 2017. Adsorption kinetics of water vapor on hypercrosslinked polymeric adsorbent and its comparison with carbonaceous adsorbents. Microporous Mesoporous Mater. 241:178–84. doi:https://doi.org/10.1016/j.micromeso.2016.12.028.

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Data availability statement

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