Measurement of diffusivity in supercritical carbon dioxide via particle dissolution method

A novel method of determining diffusivity in supercritical carbon dioxide is proposed based on the principle of particle dissolution. The dissolution rate of disperse blue 14 (DB14) was measured by in situ UV-vis spectroscopy and compared with a pseudo-steady-state diffusion-driven dissolution model. By minimizing the error between the experimental data and model equation via nonlinear regression, the diffusivities of DB14 at 21.9-25.7 MPa and 320-393 K were determined. The diffusivities were then compared with reference data measured using the chromatographic impulse response method. Positive deviations of 2.88%, 3.11%, and 1.41% were confirmed, suggesting the possibility and potential of the method. Further research is needed to determine and optimize the accuracy of the measurements and generalize the method to other systems.