Enhanced membrane distillation of organic solvents from their aqueous mixtures using a carbon nanotube immobilized membrane

In this paper, we report for the first time the application of carbon nanotube immobilized membrane (CNIM) for enhanced separation of organic solvents from their aqueous mixtures via sweep gas membrane distillation. The presence of carbon nanotubes (CNTs) on the hydrophobic membrane surface significantly altered the liquid-membrane interactions to promote isopropanol (IPA) transport in IPA-water mixture by inhibiting water penetration into the membrane pores. The preferential sorption of IPA on the CNIM was evident from the contact angle measurements. The isopropanol flux, selectivity and mass transfer coefficient obtained with CNIM were significantly higher than the corresponding unmodified PTFE membrane at different isopropanol concentrations and temperatures with enhancement in separation factor reaching as high as 350% at 70 °C. An increase in mass transfer coefficient of about 132% was also observed. Performance enhancement in CNIM was mainly attributed to the preferential sorption on the CNTs followed by rapid desorption from its surface.