Embodiments of the present invention relate to a nanofiltration composite membrane for use to purify water, the methods for preparing said nanofiltration composite membranes and to the nanofiltration composite membranes prepared accordingly.

The present disclosure provides a hydrophilic, integrally asymmetric, semi-permeable hollow-fiber membrane made from a hydrophobic aromatic sulfone polymer and at least one hydrophilic polymer, the membrane comprising an inner surface facing towards its lumen, an outer surface facing outwards and an intermediate wall having a wall thickness and comprising an open-pore separating layer and an supporting layer having an asymmetric, sponge-like structure without finger pores, wherein adjoining to the wall of the inner surface the hollow-fiber membrane comprises an essentially isotropic zone; after which the pore size abruptly start increasing up to a maximum, after which the pore size decrease again, then adjoining an essentially isotropic supporting layer which then is adjoined by the outer surface, wherein the separating layer has a cut-off of greater than 300 000 Daltons. The present disclosure further provides a method for producing such membranes and a use of the membranes for microfiltration purposes.

The present disclosure relates to a microporous hollow fiber filter membrane having a large inner diameter and a thin wall. The fiber can be used for sterile filtration of liquids or removal of particles from liquids. The disclosure further relates to a method for producing the membrane and a filter device comprising the membrane.

A method for processing a fluid with forward osmosis process includes providing one or more tubular membranes each including a tubular nonwoven base layer on the outside of the tubular membrane forming an outer shell of the tubular membrane and providing a lumen for feed flow; a polymer substrate layer on the lumen-side of the tubular membrane comprising three regions, including a region where the polymer substrate layer is partially intruded into the tubular base layer, a region with an open macrovoid structure and a region with an asymmetrical foamy layer, where the partially intruded region forms an intermediate layer; and a functional top layer on the polymer substrate layer. The tubular base layer comprises a longitudinal weld. The method includes providing the feed flow through the lumen and providing a draw solution on the outer shell side of the tubular membrane; and processing the feed flow with the membrane.

The present invention provides a method for manufacturing a porous membrane having high water permeability and hydrophilicity, which is not easily affected by a treatment such as washing, the method including: preparing, as a substrate, a membrane having a plurality of pores, which includes a water-insoluble resin such as polysulfone and a water-soluble resin including a monomer unit of polyvinylpyrrolidone or a monomer unit of polyvinyl alcohol; and irradiating the substrate with an electron beam in the presence of an aqueous solvent to crosslink at least a part of the water-soluble resin.

The present invention deals with a method for obtaining membranes in the form of hollow fibers with application in the field of carbon dioxide removal from natural gas. The aforementioned membranes are obtained by means of heat treatment of polymeric membranes. In this method, polymeric membranes are obtained by a phase-inversion technique by immersion-precipitation and are subsequently subjected to a heat treatment, that is, that the membranes effectively become precursor membranes of the heat treatment. The heat treatment process involves the optimization of the heating rate, temperature, and stabilization time variables, aiming at the improvement of the transport properties of the polymeric membranes. After the heat treatment, it becomes possible to use the membranes in separation processes of gases which operate at pressures greater than 30 bar, with selectivity for carbon dioxide (CO.sub.2).

One aspect of the present invention is a composite hollow fiber membrane including: a semipermeable membrane layer; and a supporting layer that has a hollow fiber shape and is porous, wherein the semipermeable membrane layer contains a crosslinked polyamide polymer composed of a polyfunctional amine compound and a polyfunctional acid halide compound, the supporting layer has a gradient structure in which pores of the supporting layer gradually increase in size from one of an inner surface and an outer surface to the other, has a cut-off particle size of 0.001 to 0.3 μm, and contains a crosslinked hydrophilic resin on at least a dense surface having smaller pores of the inner surface and the outer surface, and the semipermeable membrane layer is in contact with the dense surface of the supporting layer.

The disclosed technology relates to flat sheet porous membranes prepared from a dope solution containing a polymer of vinyl chloride, such as chlorinated polyvinyl chloride.

A reverse osmosis membrane is disclosed that has a hydrogel disposed on its surface, wherein the hydrogel is formed from a crosslinked polyvinylpyrrolidone or a copolymer of vinyl pyrrolidone. The hydrogel-coated membrane resists fouling by feed water contaminants. The permeate flux rate and salt rejection of the underlying membrane are not negatively affected by the hydrogel coating.

A solution contains at least one sulfone polymer and N-tert.-butyl-2-pyrrolidone. The solution can be used in a process of making a membrane, which is useful for water treatment.