Pervaporation of water-ethanol mixtures through photopolymerized acrylic membranes

UV induced copolymerization of oligomers to obtain crosslinked membranes with suitable properties for water-ethanol separation in the pervaporation process is investigated. Membranes based on bis-phenol-A-diglycidil-ether diacrylate [BGEDA] copolymerized with acrylated oligomers, poly(ethylene glycol) [PEGDA] and poly(propylene glycol) [PPGDA], have been characterized and tested in pervaporation experiments on water-ethanol mixtures. The swelling behavior of the membranes based on BGEDA-PPGDA mixtures is interpreted on the basis of the three components solubility parameter suggested by Hansen. The BGEDA-PEGDA based networks exhibit a swelling behavior with a maximum in the swelling curve at about 30% water content that cannot be explained by the Hansen treatment. For all the systems the permeation rate observed at different feed composition was found to change in agreement with the swelling ratio. By comparing the values of the permeation rate and water separation factors obtained with BGEDA-PPGDA and BGEDA-PEGDA membranes, it can be concluded that the total flux through the membrane is controlled mainly by the hydrophilic character of the structural units of the oligomers whereas the water separation factor is controlled by both the crosslinking density and the hydrophilic character of the network. (C) 1997 Elsevier Science B.V.