Bipolar membrane and preparation method thereof

Abstract

The invention discloses a bipolar membrane and a preparation method thereof. The bipolar membrane is of a three-layer structure composed of a cation exchange membrane, an anion exchange membrane and a middle interface layer between the cation exchange membrane and the anion exchange membrane, wherein the middle interface layer is prepared from a coordination compound formed by polyvinyl alcohol and a water-soluble metal ion compound. The preparation method comprises the following steps: dissolving polyvinyl alcohol and the metal ion compound in water to form a coordination compound aqueous solution of polyvinyl alcohol and the metal ion compound; coating the cation exchange membrane or anion exchange membrane with a layer of coordination compound aqueous solution, and drying to form the middle interface layer; and coating the middle interface layer with a layer of membrane liquid of the anion exchange membrane or cation exchange membrane, and drying to obtain the bipolar membrane. According to the bipolar membrane disclosed by the invention, the water dissociation voltage (voltage drop) is small, and the coordination compound cannot penetrate the anion exchange layer and cation exchange layer to be lost in the using process so that the performance of the bipolar membrane is more stable and the service life is long.

Description

technical field [0001] The invention belongs to the technical field of bipolar membrane preparation, and in particular relates to a bipolar membrane with low water dissociation voltage using polyvinyl alcohol and heavy metal ions as an intermediate interface layer and a preparation method thereof. Background technique [0002] Bipolar membrane is a new type of ion exchange composite membrane, which usually includes an anion selective layer, a cation selective layer and an intermediate interface layer between these two membrane layers. Bipolar membranes can efficiently dissociate water into hydrogen ions and hydroxide ions under the action of a reverse bias electric field, thereby converting salts in aqueous solution into corresponding acids and bases. Electrodialysis based on bipolar membranes has the advantages of simplicity, high efficiency, energy saving, and cleanliness. It has broad applications in pollution control, resource recovery, and chemical production processes,...

AI Technical Summary

Problems solved by technology

These ion exchange resins require small particle size (less than 1 micron), narrow distribution, uniform, random, and monobead distribution in the middle interface layer of the bipolar membrane, so the preparation of this bipolar membrane is very difficult and cumbersome, and the middle interface The number of catalytically active sites of the layer is limited by the amount of distributed resin, which also makes the voltage drop across the bipolar membrane higher

In Chinese patent 99125066.4, a bipolar membrane with a cross-linked network structure containing quaternary ammonium groups and tertiary amine groups is disclosed in which the intermediate interface layer is dispersed with cation exchange resins. The preparation method of this bipolar membrane is easy to realize the formation of the intermediate interface layer. Ultra-thin, but also has the disadvantages of fewer catalytic active sites and higher voltage drop on both sides of the membrane

The Chinese Patent Publication No. CN1704151A discloses a method of using dendritic polymers as the catalytic substance of the bipolar membrane intermediate interface layer. The compound is used as the method of the catalyst substance of the bipolar membrane intermediate interface layer, and the Chinese patent publication number is that CN101138707A discloses the method for using the hyperbranched polymer as the catalyst substance of the bipolar membrane intermediate interface layer, and the obtained bipolar membrane performance is stable, has the use Long life and other advantages, but the dendritic polymer (the dendritic polymer with the generation number of 2-10 that contains nitrogen atoms in the repeating unit and the outermost layer is an amine group, its initial initiating nucleus is preferably ammonia, ethylenediamine or Other polyamines such as dendritic polyethyleneimine, dendritic polypropyleneimine and dendritic polyamide), hyperbranched polymers (with pentaerythritol or trimethylolpropane as the core, 2,2-dimethylolpropane Acid is a branching unit, and the outer layer end group is hydroxyl or terminal hydroxyl modified product, including amino group, carboxyl group, sulfur group, carboxylate group, phosphate group, quaternary ammonium group) The synthesis route is complicated, the operation is difficult, and the cost is high. Its scope of application is limited

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