Separation of aroma compounds from aqueous solutions by pervaporation using polyoctylmethyl siloxane (POMS) and polydimethyl siloxane (PDMS) membranes

Pervaporation separation was used to recover aroma compounds from ethyl butanoate (ETB)–H2O, ethyl hexanoate (ETH)–H2O mixtures, and ETB–ETH–H2O mixtures using polyoctylmethyl siloxane (POMS) and polydimethyl siloxane (PDMS) membranes. The effects of operating conditions (e.g., downstream pressure, feed concentration, feed flow rate, and temperature) on the separation performance were investigated. It was shown that decreasing downstream pressure increased both permeation flux and separation factor, while an increase in feed aroma concentration and/or temperature would increase water flux more significantly than the aroma compound flux, resulting in a decrease in the separation factor. In general, the POMS membrane was more permselective to the aroma compound than the PDMS membrane, and the membrane was more efficient for separation of ETH than for ETB. When both model aroma compounds were present in the feed solution, there was a strong interaction between the two permeating components and the permeation of one aroma compound was affected by the presence of the other aroma compound. It was also shown that under the operating conditions tested, both concentration polarization and temperature polarization occurred. The feed flow hydrodynamic conditions should be controlled appropriately to reduce the boundary layer effect in order to improve the process efficiency.