Electrochemical Characteristics of Modified Heterogeneous Bipolar Membrane and Electromembrane Process of Nitric Acid and Sodium Hydroxide Recuperation from Sodium Nitrate and Boric Acid Solution

• Published in: Russian journal of electrochemistry Vol. 57; no. 2; pp. 122 - 133
• Main Authors: Kovalev, N. V., Karpenko, T. V., Sheldeshov, N. V., Zabolotsky, V. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.02.2021; Springer Nature B.V
• Subjects: Acids; Anion exchanging; Cation exchanging; Caustic soda; Chambers; Chemistry; Chemistry and Materials Science; Current efficiency; Electrochemistry; Electrodialysis; Energy consumption; Ion exchange; Membranes; Nitric acid; Physical Chemistry; Sodium; Sodium hydroxide; Sodium nitrates; boric acid; nitric acid; electrochemical impedance spectroscopy; current–voltage curve; bipolar ion-exchange membrane; sodium hydroxide; electrodialysis; sodium nitrate
• ISSN: 1023-1935; 1608-3342
• DOI: 10.1134/S1023193521020063

Characteristics of an аMB-2m bipolar membrane containing ion-polymer with phosphoric-acid groups, catalytically active in the water dissociation reaction, were studied by the electrochemical-impedance spectroscopy. The study is carried out in 0.1 М nitric acid–0.1 М sodium hydroxide system. The аMB-2m membrane bipolar region resistance is shown to be an order of magnitude less than that of the MB-1 and MB‑2 commercial membranes. The process of nitric acid and sodium hydroxide production from 0.5 М sodium nitrate solution, as well as from 0.5 М sodium nitrate solution containing 0.75 М boric acid is studied in an electrodialysis apparatus with three-chamber unit cells comprised of Ralex CMH cation-exchange membrane, аMB-2m bipolar membrane, and Ralex AMH anion-exchange membrane. The electrochemical characteristics (the current efficiency, the specific energy consumption, and the specific productivity) are shown to remain unchanged in the presence of boric acid, its transfer into the acid and alkali chambers of the electrodialyzer does not exceed 7%. A probable mechanism of the boric acid and borate ion transfer through the ion-exchange membranes into the acid and alkali chambers is suggested.