The electrochemical reduction of nitrate in acidic nitrate solutions

Cathodic regeneration of nitrous acid by electrochemical reduction of nitrates could yield a catholyte which is useful in the processing of manganiferous ores. The purpose of the present investigations was to study the cathodic reaction in an electrolytic cell with an acidic nitrate electrolyte. Electrochemical reduction of nitrate has been investigated in the ranges 0.45-2.70 M H+, 0.0-0.1 M HNO2, 0.5-2.0 M NO3- and 20-80 degrees C at several cathode materials. Potentiodynamic scanning experiments with a platinized titanium cathode showed limiting current densities of 0-300 A m(-2) at cathode potentials of + 950- + 700 mV vs SHE. At cathode potentials less than + 700 mV vs SHE, cathodic reduction of nitrous acid to nitric oxide took place. A linear relation between the nitrous acid concentration and the limiting current density was found in this experimental range. Nitrous acid can be produced by cathodic reduction of nitric acid in a membrane cell. However, the maximum concentration of nitrous acid that can be produced is limited by two reactions; decay of nitrous acid to nitric acid and nitric oxide and cathodic reduction of nitrous acid to nitric oxide.