POLYIMIDE REVERSE OSMOSIS MEMBRANE PRODUCED USING DIOXANE ANTISOLVENT AND DIMETHYL FORMAMIDE FOR LIQUID SEPARATIONS

摘要

ABSTRACT OF THE DISCLOSUREAsymmetric polyimide reverse osmosismembranes of high flux and selectivity for organicliquid separations are described. These membranes areprepared from undegraded polyimide by dissolving from14-30 wt.% of the undegraded polymer in a dual solventsystem comprising a polymer pro-solvent/anti-solventwherein the pro-solvent is DMF and the anti-solvent isdioxane, wherein the ratio of anti-solvent/pro-solventranges from about 10:1 or more-1:1, preferably about8:1-1.5:1, most preferably about 7:1-3:1; thepolymer-solvent mixture is spread into a thin film ofthe desired thickness and permitted to evaporate for atime just sufficient to permit formation of anasymmetric dense active layer, i.e., within the range2-120 seconds, preferably 2-60 seconds, most preferably2-20 seconds before being immersed in a gelation bath.The membranes may be fabricated in the formof sheets, tubes, hollow fibers, etc.Mixtures of organic liquids, and especiallymixtures of dewaxing solvents and dewaxed oils, areseparated one from the other after completion ofdewaxing operations, using the asymmetric polyimidereverse osmosis membrane described above.