The science of impregnation and the optimization of the performance of impregnated activated carbons for gas mask applications.
Date
2007
Authors
Fortier, Hubert.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Activated carbon is an amazing material from the perspective of science and technology. This material incorporates an extensive network of pores with a wide range of dimensions. Macropores (diameter > 50 nm) and mesopores (50 nm > diameter > 2 nm) lend good transport properties within a granule of activated carbon while micropores (diameter < 2 nm) have relatively strong potential wells in which foreign molecules can be physisorbed. The extensive porosity implies that activated carbon has a high specific surface area, typically 1000 m2/g, which makes it a perfect support to deposit a large amount of solid, such as a catalyst or reactant, known as the impregnant.
Mainly because of their poor affinity for activated carbon, some gases (mainly high saturation pressure gases) do not adsorb on activated carbons in the quantities required for gas mask applications. It is therefore necessary to impregnate the activated carbon with compounds that will react with (chemisorb) the target gas. The adsorption capacity for two gasimpregnant couples (NH 3 with ZnCl2 and SO2 with K2CO 3) will be discussed in terms of stoichiometric ratios of reaction. The effect of increasing the impregnant loading on the capacity for a gas for which an impregnant is intended will be characterized. The effect of increasing the impregnant loading on the capacity for gases for which the impregnant is not intended, such as cyclohexane and water vapor, will also be discussed.
Other facets of the art of impregnated activated carbon that have been neglected in the literature, but not in the course of the current work, are the kinetics of reaction on impregnated activated carbons and the thermodynamics of activated carbon impregnation. Empirical evidence will show the interconnectedness of the exclusion of salt solution from the activated carbon porosity, the drastic reduction in the maximum imbibing volume as the concentration of solution increases, and the contact angle increase on a carbonaceous surface as the solution concentration increases. The opposite trend will also be shown for preferentially adsorbed salts.
Thesis (Ph.D.)--Dalhousie University (Canada), 2007.
Mainly because of their poor affinity for activated carbon, some gases (mainly high saturation pressure gases) do not adsorb on activated carbons in the quantities required for gas mask applications. It is therefore necessary to impregnate the activated carbon with compounds that will react with (chemisorb) the target gas. The adsorption capacity for two gasimpregnant couples (NH 3 with ZnCl2 and SO2 with K2CO 3) will be discussed in terms of stoichiometric ratios of reaction. The effect of increasing the impregnant loading on the capacity for a gas for which an impregnant is intended will be characterized. The effect of increasing the impregnant loading on the capacity for gases for which the impregnant is not intended, such as cyclohexane and water vapor, will also be discussed.
Other facets of the art of impregnated activated carbon that have been neglected in the literature, but not in the course of the current work, are the kinetics of reaction on impregnated activated carbons and the thermodynamics of activated carbon impregnation. Empirical evidence will show the interconnectedness of the exclusion of salt solution from the activated carbon porosity, the drastic reduction in the maximum imbibing volume as the concentration of solution increases, and the contact angle increase on a carbonaceous surface as the solution concentration increases. The opposite trend will also be shown for preferentially adsorbed salts.
Thesis (Ph.D.)--Dalhousie University (Canada), 2007.
Keywords
Chemistry, Organic.