Study of the Production of Sodium Hydroxide by Bipolar Electrodialysis from Sodium Carbonate Solution

In this work, the production of sodium hydroxide by the method of bipolar electrodialysis from a solution of sodium carbonate using bipolar membranes MB-3 has been studied. For research, a laboratory electrodialyzer-synthesizer with a three-chamber unit cell has been used. The membrane package of the electrodialyzer has contained five elementary cells, the active area of each membrane being 1 dm². To compare the obtained mass transfer characteristics, the process of preparation of sodium hydroxide from sodium sulfate has been additionally studied. It has been shown that the use of sodium carbonate as the initial solution makes it possible to increase the concentration of the resulting alkali from 0.92 to 1.7 M under comparable process conditions compared to the preparation of sodium hydroxide from a sodium sulfate solution. When sodium carbonate is used, the alkali current efficiency is more than 70% in all experiments, while when alkali is obtained from a sodium sulfate solution, the current efficiency drops sharply to 0.4–0.5% when the concentration exceeds 0.8 M NaOH. The energy consumption for the transfer of one kg of alkali is in the range of 2.8–13.9 kWh/kg at operating current densities of 1–3 A/dm².