The influence of acid activation of bentonite in the composition of a bipolar membrane on the characteristics of the electrodialysis conversion of sodium sulphate

Abstract

The effect on the characteristics of the electrodialysis process of the acid activation of bentonite included in the cationexchange layer of an experimental bipolar membrane obtained by applying a liquid LF-4SK cation-exchange layer containing bentonite particles onto an anion-exchange membrane-substrate MA-41 was studied. Acid activation of bentonite was carried out with nitric acid (C = 1 and 4 mol/dm3) for 6 hours at temperatures of 20 and 90 °C. The conversion of sodium sulphate (C = 0.5 mol/dm3) was carried out in a six-section electrodialysis apparatus with experimental bipolar membranes containing bentonite in its original form and after acid activation. It has been shown that the addition of bentonite treated with nitric acid (C = 4 mol/dm3, t = 90 °C, t = 6 h) to the cation-exchange layer of a bipolar membrane leads to an increase in productivity, current efficiency and a decrease in energy costs compared to a membrane containing bentonite in its original form. Experimental bipolar membranes made on the basis of MA-41 and a liquid sulphonic cation exchanger containing acidactivated bentonite clays make it possible to obtain an acid and alkali performance omparable to that of the MB-3 bipolar membrane.

Keywords

• electrodialysis
• bipolar membrane
• acid activation
• bentonite
• sodium sulphate
• acid
• alkali