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Modeling adsorption of organic compounds on activated carbon: a multivariate approach
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Modellering av adsorption av organiska förreningar i aktivt kol : ett multivariat angreppssätt (Swedish)
Abstract [en]

Activated carbon is an adsorbent that is commonly used for removing organic contaminants from air due to its abundant pores and large internal surface area. This thesis is concerned with the static adsorption capacity and adsorption kinetics for single and binary organic compounds on different types of activated carbon. These are important parameters for the design of filters and for the estimation of filter service life. Existing predictive models for adsorption capacity and kinetics are based on fundamental “hard” knowledge of adsorption mechanisms. These models have several drawbacks, especially in complex situations, and extensive experimental data are often needed as inputs. In this work we present a systematic approach that can contribute to the further development of predictive models, especially for complex situations. The approach is based on Multivariate Data Analysis (MVDA), which is ideally suited for the development of soft models without incorporating any assumptions about the mathematical form or fundamental physical principles involved.

Adsorption capacity and adsorption kinetics depend on the properties of the carbon and the adsorbate as well as experimental conditions. Therefore, to make general statements regarding adsorption capacity and kinetics it is important for the resulting models to be representative of the conditions they will simulate. Accordingly, the first step in the investigations underlying this thesis was to select a minimum number of representative and chemically diverse organic compounds. The next steps were to study the dependence of the derived affinity coefficient, β, in the Dubinin-Radushkevich equation on properties of organic compounds and to establish a new, improved model. This new model demonstrates the importance of adding descriptors for the specific interaction with the carbon surface to the size and shape descriptors. The adsorption capacities of the same eight organic compounds at low relative pressures were correlated with compound properties. It was found that different compound properties are important in the various stages of adsorption, reflecting the fact that different mechanisms are involved. Ideal adsorbed solution theory (IAST) in combination with the Freundlich equation was developed to predict the adsorption capacities of binary organic compound mixtures. A new model was proposed for predicting the rate coefficient of the Wheeler-Jonas equation which is valid for breakthrough ratios up to 20%. Finally, it was shown that the Wheeler-Jonas equation can be adapted to describe the breakthrough curves of binary mixtures. New models were proposed for predicting its parameters, the adsorption rate coefficients, and the adsorption capacities for both components of the binary mixture. Thus, multivariate data analysis can not only be used to assist in the understanding of adsorption mechanisms, but also contribute to the development of predictive models of adsorption capacity and breakthrough time for single and binary organic compounds.

Place, publisher, year, edition, pages
Umeå: Kemi , 2004. , 162 p.
Keyword [en]
Analytical chemistry, activated carbon, adsorption, adsorption capacity, adsorption rate, PCA, PLS, binary mixtures, Dubinin-Radushkevich, Wheeler-Jonas
Keyword [sv]
Analytisk kemi
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-297ISBN: 91-7305-697-9 (print)OAI: oai:DiVA.org:umu-297DiVA: diva2:142987
Public defence
2004-09-24, KB3A9, KBC, Umeå Universitet, Kemi Institution, SE-90187, Umeå, 13:00
Opponent
Supervisors
Available from: 2004-08-23 Created: 2004-08-23 Last updated: 2017-01-30Bibliographically approved
List of papers
1. A systematic approach for modeling the affinity coeffcient in the Dubinin-Radushkevich equation
Open this publication in new window or tab >>A systematic approach for modeling the affinity coeffcient in the Dubinin-Radushkevich equation
Show others...
2002 In: Carbon, ISSN 0008-6223, Vol. 40, 2587-2596 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-4033 (URN)
Available from: 2004-08-23 Created: 2004-08-23Bibliographically approved
2. Modeling the influence of physico-chemical properties of volatile organic compounds on activated carbon adsorption capacity
Open this publication in new window or tab >>Modeling the influence of physico-chemical properties of volatile organic compounds on activated carbon adsorption capacity
2003 In: Carbon, ISSN 00086223, Vol. 41, 1322-1325 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-4034 (URN)
Available from: 2004-08-23 Created: 2004-08-23Bibliographically approved
3. Measurement and prediction of the adsorption of binary mixtures of organic vapors on activated carbon
Open this publication in new window or tab >>Measurement and prediction of the adsorption of binary mixtures of organic vapors on activated carbon
2001 In: Adsorption Science & Technology, ISSN 0263-6174, Vol. 19, 737-749 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-4035 (URN)
Available from: 2004-08-23 Created: 2004-08-23Bibliographically approved
4. A systematic investigation of the overall rate coefficient in the Wheeler-Jonas equation for adsorption on dry activated carbons
Open this publication in new window or tab >>A systematic investigation of the overall rate coefficient in the Wheeler-Jonas equation for adsorption on dry activated carbons
2005 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 43, no 3, 481-490 p.Article in journal (Refereed) Published
Abstract [en]

Modelling of the adsorption rate coefficient, kv of the Wheeler-Jonas equation for estimating the service life of packed carbon beds, is addressed. Current methods for extracting kv from experimental breakthrough data include approaches that introduce easily propagated errors. The weaknesses of these approaches are analyzed, and a calculation based on multiple points on the breakthrough curve is suggested. Experimental breakthrough data for a representative set of volatile organic compounds (VOCs) has been measured. A systematic investigation of factors influencing kv, including adsorbate and carbon properties, adsorbate inlet concentration and flow velocity is performed. It is found that flow velocity and carbon particle size have the largest influence, followed by adsorbate properties related to the adsorption capacity. A simple linear empirical model for kv, including air flow velocity, carbon particle size, and dielectric constant of the adsorbate, is presented. The model is based on the breakthrough range up to 20% of the inlet concentration, for which kv is shown to be almost constant. The range of the model covers breathing rates valid for a respirator at different work loads. The model can be used to estimate the adsorption rate coefficient for specific carbon particle sizes and various VOCs present in workplace environments.

Place, publisher, year, edition, pages
Oxford: Pergamon Press, 2005
Keyword
activated carbon, adsorption, modeling, adsorption properties, transport properties
National Category
Physical Chemistry Materials Engineering
Identifiers
urn:nbn:se:umu:diva-20979 (URN)10.1016/j.carbon.2004.09.024 (DOI)000226574600003 ()
Available from: 2009-03-31 Created: 2009-03-31 Last updated: 2017-12-13Bibliographically approved
5. Service life of activated carbon beds exposed to binary organic vapor mixtures
Open this publication in new window or tab >>Service life of activated carbon beds exposed to binary organic vapor mixtures
Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-4037 (URN)
Available from: 2004-08-23 Created: 2004-08-23 Last updated: 2010-01-13Bibliographically approved

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