Sorption effects of co-solvents and dissolved organic compounds on supercritical CO2 permeation through a micro-porous TiO2-membrane

The permeation and retention performance of the hydrophilic micro-porous ceramic TiO2-membrane (pore size 0.9 nm) for the separation of supercritical CO2 from high pressure extracts is the subject of this study. The influence of co-solvents (ethanol, n-hexane, water) and low-volatile organic compounds (vitamin E, PEG 600, trimyristin and other triglycerides) on CO2 permeation was investigated. A specific interaction between the membrane surface (in this paper hydrophilic) and the tested substances (polar and non-polar) caused by adsorption determines the membrane behaviour. The strong non-polar long-chained triglycerides could be separated from the CO2 with partial pore blockage, while vitamin E and PEG 600 totally blocked the membrane. The MWCO of the TiO2-membrane in the tested operating condition range was estimated 800 Da. The CO2 permeate flux during the retention experiment reached an acceptable value of 0.4 mol s−1 m−2.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We carried out experiments to separate SCCO2 from extracts by ceramic membranes. ► A micro-porous TiO2-membrane with a pore-size of 0.9 nm was investigated. ► Low-volatile organic compounds and co-solvents with different polarity were tested. ► Sorption effects and polarity of the compounds mainly influence the permeate flux. ► MWCO (800 Da) was measured with triglycerides at a permeate flux of 0.4 mol s−1 m−2.