1 research outputs found
Diffusion and Tortuosity in Porous Functionalized Calcium Carbonate
Calcium carbonate can be “functionalized”
by use
of etching agents such as phosphoric acid to create inter- and intraparticle
porosity with a range of morphologies. Functionalized calcium carbonate
has potential for use as a carrier for the delayed release of actives,
such as drugs, plant protection chemicals, and food additives such
as flavors. The drug or flavor is released slowly by permeation and
diffusion. In order to measure the effective rate of diffusion within
a range of morphologies, and hence gain insights into the optimum
mode of functionalization, the diffusion of vanillin in ethanol is
reported. Effective diffusion coefficients <i>D</i>′
were measured in a flow cell connected to a high performance liquid
chromatograph (HPLC). Samples were also subjected to mercury intrusion
porosimetry. The resulting percolation characteristics were inverse
modeled using the PoreXpert package to generate representative void
structures with estimated tortuosities. It is shown that the primary
particle size of a sample was a better predictor of <i>D</i>′ calculated from the experimental diffusion curves, and also
of the porosity-scaled tortuosity values, than the porosity or surface
area. There was also a correlation between intraparticle tortuosity,
scaled by porosity, and diffusion coefficient. The approach is validated
by experimental evidence from this and related studies