A serial filtration system for liquid purification includes a preliminary-stage reverse-osmosis (RO) module and a first-stage, high-permeability, reverse-osmosis (HiRO) module. Both modules include (a) a chamber including an inlet, a retentate outlet, and a permeate outlet, and (b) at least one membrane separating the chamber into a retentate side on an upstream side of the membrane and a permeate side on a downstream side of the membrane. The membrane in the preliminary stage is an RO membrane, while the membrane in the first stage is an oxidized membrane. The first-stage inlet is in fluid communication with the preliminary-stage, retentate outlet; and the oxidized membrane in the first stage, comprises an oxidized polyamide active layer coated on a porous support, wherein the oxidized polyamide active layer has an atomic oxygen/nitrogen ratio of at least 1.5.

The invention discloses a forward osmosis (FO) membrane containing silica nanoparticles having high permeate water flux and its manufacturing method. The FO membrane containing a plurality of silica nanoparticles comprises a substrate layer made of polysulfone and a polyamide layer disposed on the substrate layer. In the course of manufacturing the polyamide layer on the substrate layer by interfacial polymerization, the plurality of silica nanoparticles with different properties is added into the polyamide layer to obtain the FO membrane containing silica nanoparticles having high permeability and solute selectivity.

The invention a solvent-resistant polymeric nanofiltration membrane and preparation method thereof. The method includes subjecting a diamine monomer and a dianhydride monomer to cyclization imidization in a first polar organic solvent at 160 to 230° C., to form a polyimide, wherein the diamine monomer includes a diamine monomer with a carboxyl group and a diamine monomer without a carboxyl group; dissolving the polyimide in a second polar organic solvent, to form a membrane-forming solution; performing phase inversion to obtain an intermediate membrane; treating the intermediate membrane with an organic solution of a metal salt, so that the metal ion is coordinated and cross-linked with the carboxyl group in the polyimide, to obtain a solvent-resistant polymeric nanofiltration membrane, wherein the metal salt is a divalent and/or a multi-valent metal salt. The invention also discloses use of the solvent-resistant polymeric nanofiltration membrane in the separation and/or purification of a compound.

Provided is a porous composite membrane including graphene oxide sheets; nanoparticles bound to a surface of the graphene oxide sheets solely by electrostatic and/or Van der Waals interactions. The present invention also relates to a method of producing the porous composite membrane, a gas separation system including the porous composite membrane, and uses of the porous composite membrane in a process for separating H.sub.2 from a gas stream and a process for reducing H.sub.2O swelling in a graphene oxide-based membrane.

A serial filtration system for liquid purification includes a preliminary-stage reverse-osmosis (RO) module and a first-stage, high-permeability, reverse-osmosis (HiRO) module. Both modules include (a) a chamber including an inlet, a retentate outlet, and a permeate outlet, and (b) at least one membrane separating the chamber into a retentate side on an upstream side of the membrane and a permeate side on a downstream side of the membrane. The membrane in the preliminary stage is an RO membrane, while the membrane in the first stage is an oxidized membrane. The first-stage inlet is in fluid communication with the preliminary-stage, retentate outlet; and the oxidized membrane in the first stage, comprises an oxidized polyamide active layer coated on a porous support, wherein the oxidized polyamide active layer has an atomic oxygen/nitrogen ratio of at least 1.5.

A water treatment membrane and method of making water treatment membranes includes an interfacially formed polyamide layer residing upon a microporous support film and having a plurality of graphene oxide quantum dots attached to an outer surface of the polyamide layer. The polyamide layer has a permeate flux and a salt rejection performance. The permeate flux is increased by the presence of the graphene oxide quantum dots attached to the outer surface of the polyamide.

A water treatment membrane and method of making water treatment membranes includes an interfacially formed polyamide layer residing upon a microporous support film and having a plurality of graphene oxide quantum dots attached to an outer surface of the polyamide layer. The polyamide layer has a permeate flux and a salt rejection performance. The permeate flux is increased by the presence of the graphene oxide quantum dots attached to the outer surface of the polyamide.

Provided are a method for preserving a composite semipermeable membrane which is less likely to cause a decrease in the water permeability of the composite semipermeable membrane even in a high-temperature environment, a preservation solution used for the method, and a spiral membrane element including the preservation solution. A method for preserving a composite semipermeable membrane that allows monovalent ions to selectively permeate therethrough, the method includes using an aqueous solution containing an inorganic salt and/or an organic salt composed only of monovalent cations and monovalent anions as a preservation solution to be brought into contact with the composite semipermeable membrane.

The invention provides polymeric membranes with a mixed matrix and hollow fibers, with high mechanical resistance, useful in high pressure gas permeation processes such as, in particular, the removal of CO.sub.2 from raw streams resulting from oil exploration. The membranes are formed by at least one polymeric layer consisting of at least one polymer and an inorganic filler of clay mineral nanoparticles. The respective co-extrusion processes applicable to the production of said membranes are also provided herein.

The present invention relates to a method of controlling a defect structure in an MFI zeolite membrane and a method of separating xylene isomers using the MFI zeolite membrane produced by the method, and more particularly, to a method of controlling a defect structure in an MFI zeolite membrane that improves the performance of separating a xylene isomer by reducing the amount and size of defects formed in the MFI membrane structure when removing organic-structure-directing agents in the membrane through calcination at a low temperature using ozone.