Diffusive transport in pores. Tortuosity and molecular interaction with the pore wall
(English)Manuscript (preprint) (Other academic)
The self-diffusion of neat water, dimethylsulfoxide (DMSO), octanol and the molecular components in a water-DMSO solution were measured by 1H and 2H NMR diffusion experiments for those fluids imbibed into Controlled Pore Glasses (CPG). Their highly interconnected structure is scaled by pore size and shows the some pore topology independently of the size. The nominal pore diameter of the explored CPGs varied from 7.5 nm to 72.9 nm. Hence, the ∼μm mean-square diffusional displacement during the explored diffusion times was much larger than the individual pore size. Great care was taken to establish the actual pore volumes of the CPGs. In addition, transverse relaxation experiments processed by Inverse Laplace Transformation were performed to verify that the liquids explored filled exactly the available pore volume. Relative to the respective diffusion coefficients obtained in bulk phases, we observe a reduction in the diffusion coefficient that is independent of pore sizes for the larger pores and becomes larger towards the smaller pores. Geometric tortuosity governs the behavior at larger pore sizes while the interaction with pore walls becomes the dominant factor at our smallest pore diameter. The interaction with the pore wall is not just simple steric one but must in part be dependent on the specific features of the molecules explored here.
nuclear magnetic resonance, NMR, self-diffusion, interaction, pore, controlled pore glass
Research subject Chemistry
IdentifiersURN: urn:nbn:se:kth:diva-204569OAI: oai:DiVA.org:kth-204569DiVA: diva2:1085270
FunderSwedish Research Council
QC 201704182017-03-282017-03-282017-04-18Bibliographically approved