Development of crosslinked plasma-graft filling polymer membranes for the reverse osmosis of organic liquid mixtures

We have prepared crosslinked pore filling-type membranes using a plasma-graft polymerization technique to carry out the reverse osmosis (RO) of organic liquid mixtures. The grafted methyl acrylate (MA) polymer was crosslinked to improve the pressure durability. Vinyl acrylate (VA) and N,N′-methylene bis(acrylamide) (MBAAm) were used as the crosslinkers. In the RO of a conventional non-crosslinked HDPE-g-MA membrane, the permeation rate continued to increase with operating time, and the separation factor decreased to unity (i.e., no separation occurred). The HDPE-g-MA/VA membranes showed an RO separation capability, but this deteriorated after the RO experiments were repeated several times. The HDPE-g-MA/MBAAm membranes exhibited an improved stability and a reasonable separation performance at pressures as high as 12 MPa. We show that pore filling-type membranes are applicable to the RO process using crosslinked grafted polymers. The separation performance and pressure durability can be improved on if the factors influencing the membrane are optimized, e.g., the chemical structure of the crosslinker and the composition of the monomer/crosslinker mixture.