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.