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 (PAA) dip-coated asymmetric polycarbonate (PC) membrane was investigated. To improve the interface peeling of the PAA/PC composite membrane, the PC membranes were surface-modified with residual air plasma in a tubular-type reactor. The effects of molecular weight of PAA, compositions of the coating solution and the plasma treatment time on the pervaporation performances were investigated. Compared with the PAA/PC composite membrane without plasma pretreatment, the PAA/PC composite membrane with plasma pretreatment effectively prevented interface peeling. Optimal results were obtained with the PAA/PC composite membrane prepared from the PAA/ethylene glycol(EG)/aluminum nitrate = 1/2/0.05 coating solution at the 5 W/30 s plasma treatment condition. The water concentration of the permeate approaches 100 wt% and a 133 g/m2h permeation rate with a 90 wt% feed ethanol concentration at 25°C was obtained.