Organic/organic mixture separation by using novel ECTFE polymeric pervaporation membranes

Abstract

Abstract ECTFE polymeric membranes were prepared via thermally induced phase separation (TIPS) technique using N-methyl-2-pyrrolidone as latent solvent and glycerol triacetate, triethyl citrate and adipic acid as plasticizers in order to improve polymer processability. The membranes were characterized by scanning electron microscopy, mechanical and contact angle tests for better evaluate their morphological and surface properties. The affinity and the resistance of the membranes with respect to different organic solvents (i.e. ethanol, methanol, methyl tert-butyl ether, ethyl tert-butyl ether and cyclohexane) were evaluated by means of swelling tests. All the membranes showed excellent solvent resistance (after 72 h) and high affinity to polar solvents, in particular to ethanol, whereas a low affinity to non polar solvents as cyclohexane was observed. Pervaporation (PV) tests by using a binary azeotropic mixture of ethanol and cyclohexane (30.5% w/w and 69.5% w/w) were carried out at different temperatures (30, 40 and 50 °C) and permeate pressures (2, 25 and 45 mbar). In all cases an improvement of the membrane performances, in terms of total flux, was observed by increasing the temperature and/or decreasing the permeate pressure. An improvement of the selectivity was, instead, obtained when both the temperature and the permeate pressure increased. The membranes with triethyl citrate and glycerol triacetate showed higher total flux, 1.7 kg m−2 h−1 and 1.5 kg m−2 h−1, with an ethanol/cyclohexane selectivity of 15 and 16, respectively. The membrane with adipic acid showed lower total flux, 0.45 kg m−2 h−1 of, but exhibited a much higher ethanol/cyclohexane selectivity, 31.