Diffusion of Quinine with Ethanol as a Co-Solvent in Supercritical CO 2

• Published in: Molecules (Basel, Switzerland) Vol. 25; no. 22
• Main Authors: Gaponenko, Yury, Mialdun, Aliaksandr, Shevtsova, Valentina
• Format: Journal Article
• Language: English
• Published: Switzerland 17-11-2020
• Subjects: Carbon Dioxide - chemistry; Diffusion; Ethanol - chemistry; Pressure; Quinine - chemistry; Solvents - chemistry; Temperature; Taylor dispersion; ethanol cosolvent; quinine; diffusion coefficients; supercritical CO2
• ISSN: 1420-3049

This study aims at contributing to quinine extraction using supercritical CO
and ethanol as a co-solvent. The diffusion coefficients of quinine in supercritical CO
are measured using the Taylor dispersion technique when quinine is pre-dissolved in ethanol. First, the diffusion coefficients of pure ethanol in the supercritical state of CO
were investigated in order to get a basis for seeing a relative change in the diffusion coefficient with the addition of quinine. We report measurements of the diffusion coefficients of ethanol in scCO
in the temperature range from 304.3 to 343 K and pressures of 9.5, 10 and 12 MPa. Next, the diffusion coefficients of different amounts of quinine dissolved in ethanol and injected into supercritical CO
were measured in the same range of temperatures at
= 12 Mpa. At the pressure
= 9.5 MPa, which is close to the critical pressure, the diffusion coefficients were measured at the temperature,
= 343 K, far from the critical value. It was found that the diffusion coefficients are significantly dependent on the amount of quinine in a small range of its content, less than 0.1%. It is quite likely that this behavior is associated with a change in the spatial structure, that is, the formation of clusters or compounds, and a subsequent increase in the molecular weight of the diffusive substance.