# US 2015/0306545 A1 · Method for improving rejection rate of reverse osmosis membrane, rejection rate improving agent, and reverse osmosis membrane > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0306545 A1 - Document ID: US20150306545A1 - Status: Published application - Kind: A1 - Application number: 14/649,790 - Filed: 2013-12-18 - Published: 2015-10-29 - Earliest claimed: 2012-12-28 - Assignees: Kurita Water Industries Ltd. - Applicants: Kurita Water Industries Ltd. - Inventors: Kunihiro HAYAKAWA; Takahiro KAWAKATSU - Web page: https://patentgrep.com/patent/US20150306545A1 ## CPC - B01D 67/0088: {Physical treatment with compounds, e.g. swelling, coating or impregnation} - C02F 1/441: {by reverse osmosis} - C08K 5/1345: {Carboxylic esters of phenolcarboxylic acids} - C08K 5/20: Carboxylic acid amides - C08K 5/31: Guanidine; Derivatives thereof - C09D 129/04: Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids - B01D 61/025: {Reverse osmosis; Hyperfiltration} - C02F 2101/30: Organic compounds - C02F 2103/04: for obtaining ultra-pure water - C02F 2103/08: Seawater, e.g. for desalination - C02F 2103/346: {from semiconductor processing, e.g. waste water from polishing of wafers} - C02F 2209/001: Upstream control, i.e. monitoring for predictive control - C02F 2209/20: Total organic carbon [TOC] - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) - C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09) - C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D) ## Abstract To provide a method for improving a rejection rate of an RO membrane, which further improves the stability of removal performance (rejection rate) and flux stability (sustainability of contamination resistance). In a method for improving a rejection rate of an RO membrane, including a step of allowing an aqueous solution containing a polyphenol to pass through an RO membrane, the method further includes a step of allowing an aqueous solution containing at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) to pass through the RO membrane. The method preferably further includes a step of allowing an aqueous solution containing an organic compound having an amino group and having a molecular weight of 1,000 or less to pass through the RO membrane. ## Claims ### Claim 1 A method for improving a rejection rate of a reverse osmosis membrane, the method comprising a step of allowing an aqueous solution containing a polyphenol to pass through a reverse osmosis membrane, wherein the method further comprises a step of allowing an aqueous solution containing at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) to pass through the reverse osmosis membrane. ### Claim 2 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein an aqueous solution containing a polyphenol and at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) is allowed to pass through the reverse osmosis membrane. ### Claim 3 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein after the aqueous solution containing a polyphenol is allowed to pass through the reverse osmosis membrane, the aqueous solution containing at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) is allowed to pass through the reverse osmosis membrane. ### Claim 4 (depends on 3) The method for improving a rejection rate of a reverse osmosis membrane according to claim 3, wherein the aqueous solution containing at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) contains a polyphenol. ### Claim 5 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, further comprising a step of allowing an aqueous solution containing an organic compound having an amino group and having a molecular weight of 1,000 or less to pass through the reverse osmosis membrane. ### Claim 6 (depends on 5) The method for improving a rejection rate of a reverse osmosis membrane according to claim 5, wherein an aqueous solution containing a polyphenol, at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid), and an organic compound having an amino group and having a molecular weight of 1,000 or less is allowed to pass through the reverse osmosis membrane. ### Claim 7 (depends on 5) The method for improving a rejection rate of a reverse osmosis membrane according to claim 5, wherein after an aqueous solution containing a polyphenol and an organic compound having an amino group and having a molecular weight of 1,000 or less is allowed to pass through the reverse osmosis membrane, the aqueous solution containing at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) is allowed to pass through the reverse osmosis membrane. ### Claim 8 (depends on 7) The method for improving a rejection rate of a reverse osmosis membrane according to claim 7, wherein the aqueous solution containing at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amino acid) contains a polyphenol and an organic compound having an amino group and having a molecular weight of 1,000 or less. ### Claim 9 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein the polyphenol includes a tannic acid. ### Claim 10 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein the poly(amino acid) includes a polylysine. ### Claim 11 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein the modified poly(vinyl alcohol) includes at least one type selected from the group consisting of a cationic modified poly(vinyl alcohol) having a cationic group as a modifying group, an anionic modified poly(vinyl alcohol) having an anionic group as a modifying group, and a modified poly(vinyl alcohol) having a poly(alkylene oxide) chain. ### Claim 12 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein the high molecular polysaccharide includes at least one type selected from the group consisting of a xanthan gum, a guar gum, a carboxymethyl cellulose and its salt, an algin acid and its salt, and a chitosan. ### Claim 13 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein the total amount of the polyphenol and at least one type selected from the group consisting of the modified poly(vinyl alcohol), the high molecular polysaccharide, and the poly(amino acid) which is supplied to the reverse osmosis membrane and which is calculated from the concentrations in the aqueous solutions and the amounts thereof allowed to pass through the reverse osmosis membrane is set so that the weight ratio of the polyphenol to the at least one type selected from the group consisting of the modified poly(vinyl alcohol), the high molecular polysaccharide, and the poly(amino acid) is in a range of 1:0.1 to 5. ### Claim 14 (depends on 5) The method for improving a rejection rate of a reverse osmosis membrane according to claim 5, wherein the organic compound having an amino group and having a molecular weight of 1,000 or less includes arginine and/or aspartame. ### Claim 15 (depends on 5) The method for improving a rejection rate of a reverse osmosis membrane according to claim 5, wherein the total amount of the polyphenol and the organic compound having an amino group and having a molecular weight of 1,000 or less which is supplied to the reverse osmosis membrane and which is calculated from the concentrations in the aqueous solutions and the amounts thereof allowed to pass through the reverse osmosis membrane is set so that the weight ratio of the polyphenol to the organic compound having an amino group and having a molecular weight of 1,000 or less is in a range of 1:0 to 2. ### Claim 16 (depends on 1) The method for improving a rejection rate of a reverse osmosis membrane according to claim 1, wherein the pressure during the water supply is 0.1 to 0.5 MPa, and the permeation flux is 0.1 to 1.0 m3/(m2·day). ### Claim 17 (depends on 1) A reverse osmosis membrane treated by the method for improving a rejection rate according to claim 1. ### Claim 18 A rejection rate improving agent for a reverse osmosis membrane, the agent comprising a polyphenol and at least one type selected from the group consisting of a modified poly(vinyl alcohol), a high molecular polysaccharide, and a poly(amide acid). ### Claim 19 (depends on 18) The rejection rate improving agent for a reverse osmosis membrane according to claim 18, further comprising an organic compound having an amino group and having a molecular weight of 1,000 or less.