Transport and Sorption of Water Vapor in Activated Carbon
Publication: Journal of Environmental Engineering
Volume 122, Issue 3
Abstract
Control of organic vapors by adsorption on activated carbon can be impacted by the presence of water vapor in the gas stream. As a foundation to better understand this issue, the transport and sorption of water vapor within activated carbon grains was studied. Adsorption/desorption kinetics and equilibrium partitioning of water between gas and sorbed phases were determined at relative humidities (RH) in the range of 0–86% and at 20°C using an electrobalance. A model that accounts for transport within grains by pore and surface diffusion was used to interpret the sorption kinetic data. The model assumes instantaneously attained local equilibrium between sorbed and gas phases within the pores, based on a piecewise-linear isotherm measured for a small ensemble of activated carbon grains. Despite the complicated observed shape of the isotherms, including hysteresis, the model conforms well to all of the experimental data, and the asymmetry between adsorption and desorption is well resolved. The model results indicate that gas-phase diffusion dominates transport through the pores at RH ≤ 60%. Surface diffusion is found to be important at higher RH values.
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References
1.
Crank, J. (1975). The mathematics of diffusion, 2nd Ed., Oxford University Press, London, England.
2.
Crittenden, J. C., Cortright, R. D., Rick, B., Tang, S.-R., and Perram, D. (1988). “Using GAC to remove VOCs from air stripper off-gas.”J. AWWA, 80(May), 73–84.
3.
Desai, R., Hussain, M., and Ruthven, D. M. (1992). “Adsorption on activated alumina. II. Kinetic behaviour.”Can. J. Chem. Engrg., 70(Aug.), 707–715.
4.
Dubinin, M. M.(1980). “Water vapor adsorption and the microporous structures of carbonaceous adsorbents.”Carbon, 18(5), 355–364.
5.
Finlayson, B. A. (1980). Nonlinear analysis in chemical engineering . McGraw-Hill, New York, N.Y.
6.
Garg, D. R., and Ruthven, D. M.(1972). “The effect of the concentration dependence of diffusivity on zeolite sorption curves.”Chem. Engrg. Sci., 27(2), 417–423.
7.
Gray, P. G., and Do, D. D. (1989a). “Adsorption and desorption of gaseous sorbates on a bidispersed particle with Freundlich isotherm: I. Theoretical analysis.”Gas Separation and Purification, 3(Dec.), 193–200.
8.
Gray, P. G., and Do, D. D. (1989b). “Adsorption and desorption of gaseous sorbates on a bidispersed particle with Freundlich isotherm. II: Experimental study of sulphur dioxide sorption on activated carbon particles.”Gas Separation and Purification, 3(Dec.), 201–208.
9.
Gray, P. G., and Do, D. D. (1990). “Adsorption and desorption dynamics of sulphur dioxide on a single large activated carbon particle.”Chem. Engrg. Comm., 96(Oct.), 141–154.
10.
Gray, P. G., and Do, D. D.(1991). “Dynamics of carbon dioxide sorption on activated-carbon particles.”AICHE J., 37(7), 1027–1034.
11.
Gregg, S. J., and Sing, K. S. W. (1982). Adsorption, surface area and porosity, 2nd Ed., Academic Press, London, England.
12.
Hassen, N. M., Ghosh, T. K., Hines, A. L., and Loyalka, S. K. (1991). “Adsorption of water vapor on BPL activated carbon.”Carbon, 29(4-5), 681–683.
13.
Kapoor, A., and Yang, R. T.(1991). “Contribution of concentration-dependent surface diffusion to rate of adsorption.”Chem. Engrg. Sci., 46(8), 1995–2002.
14.
Kapoor, A., Yang, R. T., and Wong, C. (1989). “Surface diffusion.”Catalysis Rev.: Sci. Engrg., 31(1-2), 129–214.
15.
Leigh, C. D., and Smith, D. M.(1993). “A piecewise-linear approximation to diffusion with nonlinear interactions: Nonlinear sorption.”Chem. Engrg. Sci., 48(6), 1153–1161.
16.
Lin, T. F., Little, J. C., and Nazaroff, W. W.(1994). “Transport and sorption of volatile organic compounds and water vapor within dry soil grains.”Envir. Sci. Technol., 28(2), 322–330.
17.
Lin, T. F., Little, J. C., and Nazaroff, W. W.(1996). “Transport and sorption of organic gases in activated carbon.”J. Envir. Engrg., ASCE, 122(3), 169–175.
18.
Liu, R.-T. (1993). “Model simulation of the performance of activated carbon adsorbers for the control of indoor VOCs.”Proc., 6th Int. Conf. on Indoor Air Quality and Climate, Vol. 6, Indoor Air '93, Helsinki, Finland, 421–428.
19.
Peel, R. G., and Benedek, A.(1980). “Dual rate kinetic model of fixed bed adsorber.”J. Envir. Engrg., ASCE, 106(4), 797–813.
20.
Rudisill, E. N., Hacskaylo, J. J., and LeVan, M. D.(1992). “Coadsorption of hydrocarbons and water on BPL activated carbon.”Indus. Engrg. Chem. Res., 31(4), 1122–1130.
21.
Ruthven, D. M., and Derrah, R. I. (1972). “Sorption in Davison 5A molecular sieves.”Can. J. Chem. Engrg., 50 (Dec.), 743–747.
22.
Sing, K. S. W.(1985). “Reporting physisorption data for gas/solid systems: With special reference to the determination of surface area and porosity.”Pure & Appl. Chem., 57(4), 603–619.
23.
Tsunoda, R.(1990). “Adsorption of water vapor on activated carbons: Estimation of pore width.”J. Colloid Interface Sci., 137(2), 563–570.
24.
Wakao, N., and Funazkri, T.(1978). “Effect of fluid dispersion coefficients on particle-to-fluid mass transfer coefficients in packed beds.”Chem. Engrg. Sci., 33(10), 1375–1384.
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Copyright © 1996 American Society of Civil Engineers.
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Published online: Mar 1, 1996
Published in print: Mar 1996
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