Vallatos, A, Kirsch, RM, Williams, RA et al. (4 more authors) (2015) Probing Composition and Molecular Mobility in Thin Spherical Films Using Nuclear Magnetic Resonance Measurements of Diffusion. Industrial and Engineering Chemistry Research, 54 (26). 6825 - 6830. ISSN 0888-5885
Abstract
The composition and molecular mobility within thin spherical liquid films have been investigated using nuclear magnetic resonance (NMR) diffusion measurements. These films were formed either on the surface of pores inside a sponge at low saturation or by adsorbed water on the outside of urea prills during caking. Using pulsed field gradient (PFG) NMR experiments, the molecular mobility within these liquid films was determined through analysis of the conditional probability density for displacement (propagator). Molecular diffusion coefficients were determined for films in the sponge and prill systems by fitting the experimental propagators using a model for diffusion on an array of isotropically distributed infinite planes. By comparing these diffusion coefficients with bulk diffusion coefficients for a range of concentrations of urea solutions (2.1 M, 6.2 M and saturated), it was possible to optimize the PFG experimental parameters to enable accurate determination of molecular diffusion in these spherical liquid films. Determination of the diffusion coefficients for a range of urea solutions in the sponge enabled identification of the composition of the film that formed on the surface of the urea prills. Analysis of these data showed that the liquid layers are composed of saturated urea solution covering the surface of the prills, with an estimated layer thickness on the order of 10–5 m. The shape of the propagators indicated the adsorbed water was uniformly distributed over the surface of the urea prills, rather than primarily in the meniscus between particles, which agrees with dye visualization experiments on a pair of urea prills during caking. This work provides the first quantitative measurements of diffusion in thin spherical films, which is a key parameter for determining what controls the presence and rate of bonding between adjacent particle surfaces.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Industrial and Engineering Chemistry Research after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.iecr.5b01700. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) > Institute for Particle Science and Engineering (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 29 Sep 2015 15:29 |
Last Modified: | 06 Jul 2016 09:54 |
Published Version: | http://dx.doi.org/10.1021/acs.iecr.5b01700 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.iecr.5b01700 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:89528 |