Methods, systems and compositions for recovery of regenerant ions from spent regenerant solution by utilization of electrodialysis are provided. For example, in certain aspects methods for separating spent regenerant using an electrodialysis system comprising selective membranes are described. Furthermore, the invention provides methods for treating a friable solid ion-removal material to prevent fragmentation during regeneration.

The present invention relates to the preparation of novel anion exchange membranes from bicomponent or tricomponent copolymers containing both quaternizable and cross-linkable moieties. The bicomponent copolymers consisted with polyacrylonitrile and poly(2-dimethylaminoethyl) methacrylate and the tricomponent copolymers consisted with polyacryloniterle and poly2-dimethylaminoethyl) methacrylate and polyn-butyl acrylate. Quaternization of dimethyl amino groups of copolymer by methyl iodide followed by cross-linking of acrylonitrile groups of copolymer by hydrazine hydrate resulted anion exchange membrane with desired properties such as high ion exchange capacity (1.30-1.50 meqg.sup.−1), high transport number (0.92-0.93) for direct use in electrodyalysis unit. The tricomponent anion exchange membrane containing 32 wt % PDMA, 17 wt % PnBA, and 51 wt % PAN exhibited improved performance mainly in terms of low power consumption and high current efficiency during desalination of water.

The present invention relates to the preparation of novel anion exchange membranes from bicomponent or tricomponent copolymers containing both quaternizable and cross-linkable moieties. The bicomponent copolymers consisted with polyacrylonitrile and poly(2-dimethylaminoethyl) methacrylate and the tricomponent copolymers consisted with polyacryloniterle and poly2-dimethylaminoethyl) methacrylate and polyn-butyl acrylate. Quaternization of dimethyl amino groups of copolymer by methyl iodide followed by cross-linking of acrylonitrile groups of copolymer by hydrazine hydrate resulted anion exchange membrane with desired properties such as high ion exchange capacity (1.30-1.50 meqg.sup.−1), high transport number (0.92-0.93) for direct use in electrodyalysis unit. The tricomponent anion exchange membrane containing 32 wt % PDMA, 17 wt % PnBA, and 51 wt % PAN exhibited improved performance mainly in terms of low power consumption and high current efficiency during desalination of water.

Ion exchange membranes may comprise a polymeric microporous substrate and a cross-linked ion transferring polymeric layer on the substrate. The cross-linked ion transferring polymeric layer may comprise a polymerization product of at least a functional monomer and a low value r.sub.2/r.sub.s monomer. The ion exchange membranes may have an apparent permselectivity of at least about 95% and a resistivity of less than about 1.5 Ohm-cm.sup.2.

In a process for the purification of a liquid-crystal mixture (7), the liquid-crystal mixture (7) is passed through a first electrodialysis cell (2) and a concentrate solution (14) is passed through a second electrodialysis cell (8) which is adjacent to the first electrodialysis cell (2) and is separated by an ion-exchanger membrane (9), and an electric field transverse to a direction of passage of the liquid-crystal mixture (7) through the first electrodialysis cell (2) is generated with the aid of an anode/cathode arrangement (15, 16) arranged outside the electrodialysis cells (2, 8) so that ionized constituents of the liquid-crystal mixture (7) are discharged at the ion-exchanger membrane (9) and removed from the liquid-crystal mixture (7).

In a process for the purification of a liquid-crystal mixture (7), the liquid-crystal mixture (7) is passed through a first electrodialysis cell (2) and a concentrate solution (14) is passed through a second electrodialysis cell (8) which is adjacent to the first electrodialysis cell (2) and is separated by an ion-exchanger membrane (9), and an electric field transverse to a direction of passage of the liquid-crystal mixture (7) through the first electrodialysis cell (2) is generated with the aid of an anode/cathode arrangement (15, 16) arranged outside the electrodialysis cells (2, 8) so that ionized constituents of the liquid-crystal mixture (7) are discharged at the ion-exchanger membrane (9) and removed from the liquid-crystal mixture (7).

Highly energy efficient electrodialysis membranes having low operating costs and a novel process for their manufacture are described herein. The membranes are useful in the desalination of water and purification of waste water. They are effective in desalination of seawater due to their low electrical resistance and high permselectivity. These membranes are made by a novel process which results in membranes significantly thinner than prior art commercial electrodialysis membranes. The membranes are produced by polymerizing one or more monofunctional ionogenic monomers with at least one multifunctional monomer in the pores of a porous substrate.

Highly energy efficient electrodialysis membranes having low operating costs and a novel process for their manufacture are described herein. The membranes are useful in the desalination of water and purification of waste water. They are effective in desalination of seawater due to their low electrical resistance and high permselectivity. These membranes are made by a novel process which results in membranes significantly thinner than prior art commercial electrodialysis membranes. The membranes are produced by polymerizing one or more monofunctional ionogenic monomers with at least one multifunctional monomer in the pores of a porous substrate.

An apparatus and method for abating scale formation during the purification and demineralization of water in an electrochemical deionization apparatus. In the apparatus and method, scale forming ions in a raw water feed are precipitated at a controlled location remote from the deionization chambers of the deionization apparatus. Concentrate water produced during the deionization process to produce demineralized product water is acidified and circulated through the deionization apparatus to prevent scale formation and build-up in the deionization apparatus.

The present invention relates to a bipolar ion exchange sheet and a manufacturing method therefor, the bipolar ion exchange sheet comprising: a cation exchange film comprising a cation adsorption sheet and a cation exchange coating layer formed on one side of the cation adsorption sheet; and an anion exchange film comprising an anion adsorption sheet and an anion exchange coating layer formed on one side of the anion adsorption sheet, wherein the cation exchange film and the anion exchange film are bonded so that the cation exchange coating layer and the anion exchange coating layer face each other.