Obtaining bentonite-modified bipolar ion-exchange membranes and study of their electrochemical characteristics

Experimental samples of bipolar ion-exchange membranes made of a liquid sulfonic cation exchanger (LF-4SK) with bentonite clays (natural and organomodified) and an anion-exchange membrane MA-41 were obtained. A quaternary ammonium salt, alkyldimethylbenzylammonium chloride (surfactant), was used as an organomodifier. As a result of the treatment of bentonite with a surfactant, its surface becomes organophilic and more compatible with the organic polymer, and the interplanar distance also increases. Experimental bipolar membranes have better characteristics in terms of generation of hydrogen and hydroxyl ions during the conversion of sodium sulfate than heterogeneous bipolar membranes with similar functional groups in the cation- and anion-exchange layer, which are commercially available.The bipolar membrane with the addition of organoclay (2% wt.) showed a higher productivity in terms of H+ - ions in comparison with the membrane containing natural, unmodified bentonite samples in the cation-exchange layer. The use of organomodified bentonite in the cation-exchange layer of the prototype membrane has increased the concentration of target products and significant decreased in energy consumption per unit of the target product. The effect of bentonite clay on the characteristics of the bipolar membrane is explained by the presence of hydroxyl and silicon groups in the clay, which are catalysts for the dissociation of water molecules. A technological scheme has been developed for obtaining an experimental bipolar bentonite-modified membrane, the main stages of which are: preparation of bentonite (drying and grinding); treatment of bentonite clay with alkyldimethylbenzylammonium chloride; treatment of organoclay suspension and liquid sulfonic cation exchanger LF-4SK with ultrasound; application of the resulting suspension onto a substrate membrane - an anion-exchange membrane with quaternary ammonium groups MA-41.