Provided are a CO.sub.2 gas separation membrane, a method for manufacturing the same, and a carbon dioxide gas separation membrane module including the same, the CO.sub.2 gas separation membrane including: a first layer (A) containing at least one alkali metal compound selected from the group consisting of an alkali metal carbonate, an alkali metal bicarbonate and an alkali metal hydroxide, and a first resin in which a polymer having a carboxyl group has been crosslinked; a second layer (B) containing at least one of the alkali metal compounds, and a second resin having a structural unit derived from a vinyl ester of a fatty acid; and a hydrophobic porous membrane (C).

Provided is a scale inhibitor for RO membranes which effectively inhibits the precipitation of calcium carbonate in an RO membrane treatment without increasing the phosphorus concentration in effluent and which can be used even in the RO membrane treatment of feed in which high-M-alkalinity concentrate having a calcium hardness level of 100 to 600 mg/L-CaCO.sub.3 and an M alkalinity of 1000 to 16000 mg-CaCO.sub.3/L is produced. A scale inhibitor for reverse osmosis membranes which inhibits the formation of calcium carbonate scale in an RO membrane treatment, the scale inhibitor including components (A) and (B) below. An RO membrane treatment method including adding the scale inhibitor for RO membranes to RO feed. Component (A): Terpolymer of maleic acid, an acrylic acid alkyl ester, and vinyl acetate, Component (B): Homopolymer of carboxylic acid

Described herein is a filtration media comprising: (i) a first filtration medium comprising an anion exchange nonwoven substrate, wherein the anion exchange nonwoven substrate comprises a plurality of quaternary ammonium groups; and (ii) a second filtration medium comprising a functionalized microporous membrane wherein the functionalized microporous membrane comprises a plurality of guanidyl groups; wherein the first filtration medium is positioned upstream of the second filtration medium.

A method for manufacturing a self-healing hydrogel-filled separation membrane for water treatment includes soaking a porous support comprising pores in a monomer solution to fill the pores with the solution, removing the excessively filled monomer solution from the porous support, and forming a hydrogel in the pores by crosslinking the monomer. The separation membrane does not require an additional repair process when damage occurs to the separation membrane and can exhibit superior self-healing effect and physical stability.

Nanostructured polyelectrolyte bilayers deposited by Layer-by-Layer deposition on nanoporous membranes can be selectively crosslinked to modify the polyelectrolyte charge density and control ionic selectivity independent of ionic conductivity. For example, the polyelectrolyte bilayer can comprise a cationic polymer layer, such as poly(ethyleneimine), and an anionic polymer layer, such as poly(acrylic acid). Increasing the number of bilayers increases the cation selectivity when the poly(ethyleneimine) layer is crosslinked with glutaraldehyde. Crosslinking the membranes also increases the chemical and mechanical strength of the polyelectrolyte films. This controllable and inexpensive method can be used to create ion-selective and mechanically robust membranes on porous supports for a wide range of applications.

An acidic gas separation membrane sheet causes an acidic gas to selectively permeate therethrough. The acidic gas separation membrane sheet includes a first porous layer, a hydrophilic resin composition layer, and a second porous layer in this order. A second peel strength between the second porous layer and the hydrophilic resin composition layer is less than a first peel strength between the first porous layer and the hydrophilic resin composition layer. An average value of the second peel strength is within a range of greater than or equal to 5 N/m and less than or equal to 500 N/m.

The present disclosure provides a method of producing a cation exchange polymer, the method includes polymerizing an anionic monomer in the presence of a polymerizable crosslinker having a cationic functional group. A sufficient amount of anionic monomer is used to provide both the anionic charges necessary for cation exchange, and the anionic charges necessary to pair with the cationic functional groups in the crosslinker.

The present invention provides a gel containing a crosslinked polymer having at least one selected from the group consisting of an acidic dissociative group, an acidic dissociative group in a salt form, and a derivative group of an acidic dissociative group, and a condensate of a compound represented by the following formula (I): Si{R.sup.1N(R.sup.2)(R.sup.3)}(OR.sup.4)(OR.sup.5)(R.sup.6) (wherein each group is as defined in the DESCRIPTION).

A separation composite membrane, including a porous support layer, and a separation layer provided on the porous support layer and contains the following polymer a1 and b1; a separation membrane module; a separator; and a composition for forming a membrane suitable for preparing the separation composite membrane.

Polymer a1: A polymer whose ratio of a permeation rate of carbon dioxide to a permeation rate of methane is 15 or greater, and the permeation rate of the carbon dioxide is smaller than that in the polymer b1 and which has a solubility parameter of 21 or greater

Polymer b1: A polymer whose permeation rate of carbon dioxide is 200 GPU or greater, and a ratio of the permeation rate of the carbon dioxide to methane is smaller than that in the polymer a1 and which has a solubility parameter of 16.5 or less

The present invention provides a composition for a CO.sub.2 gas separation membrane containing: at least one compound selected from the group consisting of an alkali metal carbonate, an alkali metal bicarbonate, and an alkali metal hydroxide; a crosslinked polymer in which a polymer having a carboxyl group has been crosslinked; and a non-crosslinked polymer obtained by polymerization of one or more monomers selected from the group consisting of vinyl acetate, acrylic acid, methacrylic acid, and a derivative thereof.