Abstract: To prevent the deterioration of the flux and salt rejection characteristics of polyamide, thin-film, composite reverse osmosis membranes when subjected to relatively high temperature drying conditions, an unsubstituted inorganic ammonium cation salt of an acid is incorporated into the process of manufacture. The ammonium salt can be introduced into the process either before or after the membrane is formed by interfacial polymerization so long as it is added before the membrane is heated.

Abstract: A method of separating water of reduced concentration of a selected solute via reverse osmosis, wherein the selected solute is sulfuric acid, sodium hydroxide, isopropanol, sodium nitrate or another solute having a much higher solute passage than sodium chloride. The reverse osmosis membrane is prepared by treating a crosslinked, polyamide discriminating layer with an amine-reactive reagent or compatible oxidant at conditions whereby the passage of the selected solute at a selected transmembrane pressure is reduced by at least 30 percent.

Abstract: A reverse osmosis membrane having improved rejection of sulfuric acid and/or isopropanol is described. The membrane is prepared by treating a crosslinked, polyamide discriminating layer with an amine-reactive reagent selected from a carboxylic acid ester, a carboxylic acid anhydride, an amine-reactive organic halogen compound, an ethylenically unsaturated hydrocarbon, or a 1,3-propane sultone, at conditions whereby the passage of sulfuric acid in a 2 percent aqueous solution at a transmembrane pressure of 400 psi is reduced by at least 30 percent.

Abstract: A reverse osmosis membrane having improved rejection of sulfuric acid and/or isopropanol is described. The membrane is prepared by treating a crosslinked, polyamide discriminating layer with a compatible oxidizing reagent, such as peracetic acid, periodic acid or chloramine, whereby the passage through the treated membrane of sulfuric acid in a 2 percent aqueous solution at a transmembrane pressure of 400 psi is reduced by at least 30 percent.

Abstract: A novel hyperfiltration membrane and process for making the same is described. The membrane is useful for processing copper electroless solutions to concentrate for re-use salts of chelating agents. The membrane can be prepared by crosslinking a water-compatible polymer in the presence of a strong mineral acid, such as phosphoric acid.

Abstract: A method of improving the properties of a reverse osmosis membrane having a polyamide discriminating layer containing residual aromatic primary amine groups is described. In this method, the polyamide discriminating layer of the membrane is treated with an aqueous solution of a reagent which reacts with primary amine groups to form diazonium salt groups or derivatives of diazonium salt groups. This method results in a membrane possessing improved chlorine resistance. When nitrous acid is employed as the reagent in the treatment, the water flux of the polyamide membrane is frequently increased with little or no effect on the salt rejection of the membrane.

Abstract: A novel hyperfiltration membrane and process for making the same is described. The membrane is useful for processing copper electroless solutions to concentrate for re-use salts of chelating agents. The membrane can be prepared by crosslinking a water-compatible polymer in the presence of a phosphorus-containing acid, such as phosphoric acid, wherein the acid is present in a sufficient amount to catalyze crosslinking and to form a plurality of pores in the coating when dried.

Abstract: A novel water softening membrane and process for making the same is described. The membrane can be prepared by treating a polyamide reverse osmosis membrane with a strong mineral acid followed by treatment with a rejection enhancing agent. The resulting membrane at transmembrane pressures of 50 psi can attain a magnesium sulfate rejection with a 0.2 percent aqueous solution of more than 90 percent with a water flux of more than 15 gallons per square foot per day.

Abstract: An improved reverse osmosis membrane and process for making the same is described. The membrane is prepared by treating a polymer bearing primary amine groups with nitrous acid or a diazonium compound so as to react the resulting diazonium groups with other groups present. The resulting membrane possesses improved chlorine resistance. When the nitrous acid treatment is employed, the water flux of a polyamide membrane is frequently increased with little or no effect on the salt rejection of the membrane.

Abstract: A novel water softening membrane and process for making the same is described. The membrane can be prepared by treating a polyamide reverse osmosis membrane with a strong mineral acid followed by treatment with a rejection enhancing agent. The resulting membrane at transmembrane pressures of 50 psi can attain a magnesium sulfate rejection with a 0.2 percent aqueous solution of more than 90 percent with a water flux of more than 15 gallons per square foot per day.

Abstract: A novel water softening membrane and process for making the same is described. The membrane can be prepared by treating a polyamide reverse osmosis membrane with a strong mineral acid followed by treatment with a rejection enhancing agent. The resulting membrane at transmembrane pressures of 50 psi can attain a magnesium sulfate rejection with a 0.2 percent aqueous solution of more than 90 percent with a water flux of more than 15 gallons per square foot per day.

Abstract: Good salt rejection and flux characteristics can be obtained with reverse osmosis membranes made from crosslinked, interfacially polymerized aromatic polyamides, particularly poly(arylenepolyamine aromaticpolycarboxylamides) such as poly(phenylenediamine trimesamide). The aromatic polyamides are preferably synthesized directly from an essentially monomeric polyacyl halide (at least tri- or higher in acyl functionality) and an essentially monomeric arylene polyamine with a measurable water solubility. As compared to closely analogous linear polymers, these interfacially polymerized, crosslinked polyamides have a lower % elongation and lower solubility (e.g. in amide solvents). Chlorine resistance characteristics of these polyamides are also good and can be improved by treatment with a chlorinating agent. In the preferred practice of the method for making a reverse osmosis membrane, a porous support layer is coated with the polyamine component (e.g.

Abstract: A composite permselective membrane is prepared by reaction of a film or layer containing cycloaliphatic polyfunctional secondary amines with a triacyl halide or its mixture with a diacyl halide. The membrane is useful in separating components of fluid mixtures or solutions, such as the removal of salts from aqueous solutions by reverse osmosis.

Abstract: A reverse osmosis membrane is prepared by reaction of a film or layer of polyethylenimine with a polyfunctional reagent whose functional groups are capable of reacting with amine groups. The polyfunctional reagent is preferably a water-soluble, aromatic or heterocyclic compound having acid chloride or isocyanate functional groups.The membrane is preferably prepared in situ on a polysulfone or chlorinated polyvinyl chloride support by initial formation of a layer of polyethylenimine on the support, followed by interfacial reaction with the polyfunctional reagent to produce a thin surface coating possessing salt barrier characteristics.