Speaker
Description
Alkaline halide melts and alkaline earth metals are used for the electrochemical reduction of metal oxides to their metallic forms. In practice, fluoride, chloride, and mixed chloride-fluoride melts of alkali and alkaline earth metals are used most often. Graphite is usually applied as an inert anode material in these media. However, during the electrolysis of oxide-halide melts, carbon is not an inert anode. In recent years, metals and their alloys, metal oxides, and cermets have been considered to be the candidate inert anode materials for the electrolysis of oxide-halide melts. Almost all investigated metal anodes made of individual metals such as iron, nickel, copper, chromium, and their alloys, except some noble metals are unstable in an oxygen atmosphere and oxidize at high temperatures.
At present, oxide-chloride melts based on LiCl is used for the electrolytic reduction of uranium and plutonium oxides with lithium formed at the cathode. Platinum metal is usually used as the anode material for oxygen evolution in these melts. However, platinum is highly susceptible to corrosion in these melts and therefore is not the inert anode material. Also, platinum is an expensive metal, which makes it difficult to use as an anode material in the industry. We have carried out studies of anodic processes and electrolysis tests on the ceramic anode NiO-Li2O in LiCl-KCl-Li2O melts. Studies have shown that ceramics NiO-Li2O is the inert anode material for electrolysis of LiCl-KCl-Li2O melts at temperatures of 550-650˚C. Voltammetric studies have shown that two electrode processes can occur on the NiO-Li2O anode: 1) oxidation of oxide ions with the formation of gaseous oxygen up to potentials of 2.8-2.9 V vs E (Li+/Li) and 2) chlorination of the anode material at potentials more positive than 3.0-3.1 V vs E (Li+/Li). Experiments carried out in the process of electrolytic reduction of UO2 and UO2 with additions of rare earth oxides shown that NiO-Li2O is found to be the inert anode material. The anode current efficiency of oxygen evolution at this anode is close to 100%. As a result of electrolysis experiments during 35 h, the diameter and length of the anode sample did not decrease. Thus, ceramics NiO-Li2O can be used as the inert anode material for electrolysis of oxide-chloride melts based on LiCl.
| Speaker's title | Mr |
|---|---|
| Speaker's email address | Dealev@mail.ru |
| Country/Int. organization | Russian Federation |
| Affiliation/Organization | Institute of High-Temperature Electrochemistry |
