Dehydration of ethanol/water mixtures by pervaporation with composite membranes of polyacrylic acid and plasma-treated polycarbonate

For the purpose of separating aqueous alcohol solution mixtures by the use of the pervaporation technique, a composite membrane of polyacrylic acid (P AA) dip-coated asymmetric polycarbonate (PC) membrane was investigated. To improve the interface peeling of the PAA/PC composite membrane, the PC memb ranes were surface-modified with residual air plasma in a tubular-type reac tor. The effects of molecular weight of PAA, compositions of the coating so lution and the plasma treatment time on the pervaporation performances were investigated. Compared with the PAA/PC composite membrane without plasma p retreatment, the PAA/PC composite membrane with plasma pretreatment effecti vely prevented interface peeling. Optimal results were obtained with the PA A/PC composite membrane prepared from the PAA/ethylene glycol(EC)/aluminum nitrate = 1/2/0.05 coating solution at the 5 W/30 s plasma treatment condit ion. The water concentration of the permeate approaches 100 wt% and a 133 g /m(2)h permeation rate with a 90 wt% feed ethanol concentration at 25 degre es C was obtained. (C) 2000 Elsevier Science B.V. All rights reserved.