A base stable semipermeable membrane and methods thereof

A method of forming a semipermeable membrane having enhanced alkaline stability, wherein comprising steps of:

• a. providing an ultrafiltration (UF) base membrane;
• b. immersing said UF membrane in a solution comprising at least one substance selected from the group consisting of a polymer preferably polyethylenimine (PEI), a condensate solution and a mixture thereof, thereby forming reactive moieties upon said UF membrane;
• and,
• c. forming at least one first layer upon at least portion of said UF base support membrane by immersing said UF base support membrane of step (b) in a solution comprising at least one ingredient selected from the group consisting of polymer preferably polyethylenimine (PEI), condensate solution and a mixture thereof thereby, forming a cross-linked skin on the surface of said base membrane.

The method according to claim 102, wherein at least one of the following holds true:

• a. said diazine or triazine-containing monomer or oligomer is selected from the group consisting of:
• R1 is independently selected at each occurrence from bromo, chloro, iodo, fluoro, —NHR5, —OR5 and SR5, wherein R5 is independently selected at each occurrence from H, optionally substituted alkyl and optionally substituted aryl;
• R2 is independently selected at each occurrence from bromo, chloro, fluoro, —NHR5, —OR5 and SR5, wherein R5 is independently selected at each occurrence from H, optionally substituted alkyl and optionally substituted aryl;
• R3 is independently selected at each occurrence from bromo, chloro, fluoro, —NHR5, —OR5 and SR5, wherein R5 is independently selected at each occurrence from H, optionally substituted alkyl and optionally substituted aryl;
• R4 is selected from H, bromo, chloro, fluoro, —NHR5, —OR5 and SR5, wherein
• R5 is independently selected at each occurrence from H, optionally substituted alkyl and optionally substituted aryl;
• and
• R8 is independently selected at each occurrence from —NH2- and —NH-A-NH—, wherein A is selected from C1-2O aliphatic moieties, C6-10 aromatic moieties, and combinations thereof;
• provided that at least two occurrences, R1, R2, R3 and R4, taken together, are selected from bromo, chloro and fluoro, and further provided that when both R1 and R2 on a single ring are Cl, at least one of R3 and R4 is not Cl;
• b. said multifunctional amine has a molecular weight of in the range of 400 to 750,000;
• c. said method additionally comprising step of forming a membrane having rejection of more than 95% Glucose in 5% glucose feed solution;
• d. said membrane after soaking in 20% w/w NaOH in water at 400 C yield more than 97% glucose rejection (FIG. 1);
• e. said membrane applied pressure of about 10 bars to 40 bars in 3.5% NaOH solution at 400 C is in direct correlation with the membrane flux

A method of forming a semipermeable membrane having enhanced stability to solvent and acid, comprising steps of:

• a. providing a ultrafiltration (UF) base membrane;
• b. immersing said UF membrane in a condensate solution to form reactive moieties upon said UF membrane;
• and,
• c. immersing said UF base support membrane of step (b) in said solution comprising polymer preferably polyethylenimine (PEI), thereby forming a cross-linked skin on the surface of said base membrane.