Pervaporation of water/isopropanol mixtures through polyaniline membranes doped with poly(acrylic acid)

Abstract

Polyaniline (PANi) was synthesized by oxidative polymerization and doped with poly(acrylic acid) (PAAc) for pervaporation of aqueous isopropanol. PANi membranes were prepared by solution blending with N-methyl pyrrolidone (NMP) and exhibited the high oxidation stability enough to adopt as dehydration membranes. The conformational hindrance and bulkiness of PAAc chains caused PANi membranes disordered structures. The d-spacings of PANi/PAAc indicated a strong interaction between these two polymers by complexation. When the content of PAAc in doped membrane was 20 wt%, water concentration in permeate decreased to 97 wt%, while permeate flux increased to ca. 200 g/m 2 h due to the affinity of PAAc toward water. Water flux of PANi/PAAc membrane increased with PAAc mixing ratio of up to 30 wt%. Membranes containing more than 30 wt% PAAc showed the analogous results that flux and water concentration in permeate were about 300 g/m 2 h and ∼100 wt%, respectively. Permeate flux through PANi/PAAc membrane decreased with increasing feed IPA concentration while water concentration in permeate was maintained to be over 85 wt%. Water concentration in permeate was much higher than IPA concentration because of high affinity of PANi complex membrane toward water molecules. The activation energy for permeation from an Arrhenius-type expression was ca. 50 KJ/mol.