Dynamics of a semi-batch adsorber with constant molar supply rate: a method for studying adsorption rate of pure gases

1H NMR Investigations of Activated Carbon Loaded with Volatile Organic Compounds: Quantification, Mechanisms, and Diffusivity Determination

Three volatile organic compounds (VOCs), benzene, cyclohexane, and dichloromethane, were adsorbed onto activated carbon fiber cloth. ¹H (magic-angle spinning (MAS) and pulsed field gradient (PFG)) NMR techniques were carried out, and the signals were analyzed in terms of peak surface areas and shifts. These techniques were shown to be very useful for determining (i) the intrinsic quantification of adsorbed molecules (VOCs and/or water) in the porosity of the materials (the adsorption capacities ranged from 0.2 to 4 mol·kg^-1); (ii) the mechanisms of interactions between adsorbed organic molecules and the carbon walls (illustrations of positions of the molecule inside the pore volume are proposed; the proton-wall distance was less than 0.15 nm); and (iii) the diffusivities (surface diffusion coefficients (D_S) were estimated at ≈4.10^-12 m²·s^-1 for cyclohexane, ≈1.10^-11 m²·s^-1 for benzene, and ≈4.10^-11 m²·s^-1 for dichloromethane).

Adsorptive and Membrane-Type Separations: A Bibliographical Update (1995)

This paper provides a bibliography of the 1995 journal literature for adsorptive and membrane-type separations. The references are taken from the 50 most important chemical engineering journals. This paper provides an update to the literature as provided in previous bibliographic papers (Ray 1990a, 1991, 1994, 1995, 1996). A bibliography of the chemical engineering journal literature from 1967–1988 has been published by the author (Ray 1990b), and can provide access to a wider range of topics. A complete bibliographic listing of the chemical engineering journal literature from 1989 to 1995 (with subsequent six-monthly updates) is available on a CD-ROM database and full details can be obtained from the author.

The papers included have been divided into the following subject groups: theory; design data; adsorbents; PSA and cyclic systems, and applications; liquid-phase adsorption; ion exchange, chromatography, etc.; membranes; and membrane-type separations.

Diffusion of condensable vapors in single adsorbent particles measured via concentration-swing frequency response

A concentration-swing frequency response method is extended to examine mass transfer mechanisms and the concentration dependence of mass transfer rates for adsorption of condensable vapors in single adsorbent particles. The adsorption kinetics of water and hexane in BPL activated carbon and the adsorption of water in silica gel are determined at several different concentrations. The mechanism that best describes the adsorption of water in BPL activated carbon is nanopore diffusion. The diffusivity of water in BPL activated carbon has a clear minimum at approximately P/Po = 0.5, and the concentration dependence of the diffusion data are not described well by the Darken relationship. Both nanopore diffusion and the Glueckauf linear driving force models can be used to describe the diffusion of hexane in BPL activated carbon for the pressure range studied, and the dependence of the diffusivity on concentration can be described approximately using the Darken relationship. However, the diffusion of water in silica gel cannot be described by the nanopore diffusion model and is best characterized by the Glueckauf linear driving force model. The results illustrate the ability of concentration-swing frequency response to accurately determine adsorption rate mechanisms and quantify the complex adsorption kinetics of condensable vapors using small quantities of adsorbent.