Separation of aqueous phenol through polyurethane membranes by pervaporation. III. Effect of the methylene group length in poly(alkylene glycols)

Separation of phenol from dilute aqueous solution through polyurethane memb ranes by pervaporation was investigated. The effect of the methylene group length in poly(alkylene glycols) on permselectivity and solubility of pheno l was studied. The poly(alkylene glycols) were obtained by polycondensation of 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol with a sulfuric aci d catalyst. Polyethyleneglycol and polytetramethyleneglycol were commercial ly available. Progress of the polymerization in the poly(alkylene glycols) was confirmed by FTIR, H-1-NMR analysis, and SEC measurement. The polyureth anes were obtained by polyaddition reaction of 1,6-hexamethylenediisocyanat e and the poly(alkylene glycol), and were confirmed by FTIR analysis and SE C measurement. The phenol concentration in a permeate liquid increased from 25.1 to 36.2 wt %, and the phenol partial flux also increased from 49.3 to 68.9 g . m(-2) . h(-1) with increasing the methylene group length in the p oly(alkylene glycols), whereas the water partial flux slightly decreased. A s a result of sorption measurements, the change in the degree of swelling w as small, and the phenol concentration in the membrane increased from 42.1 to 70.8 wt %. The increase in the methylene group length of the poly(alkyle ne glycols) should contribute to an increase in the hydrophobicity of the p olyurethane so that the solubility of phenol to the membrane should increas e. The phenol concentration in the permeate liquid and the phenol partial f lux increased with an increase in the methylene group length of the poly(al kylene glycols) due to the increase in the phenol solubility for the polyur ethane membranes. (C) 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 654 -664, 2000.