Rhenium Electrowinning in the KF-KBF₄-B₂O₃-KReO₄Melt

Abstract

The rhenium electrodeposition from the KF-KBF 4 -B 2 O 3 -KReO 4 melts at 773 K was studied by the cyclic voltammetry. Two waves were found on the E(i) dependences in the cathode region corresponding to the reduction of Re (VII) to metallic Re: Re 7+ +3e→Re 4+ , and Re 4+ +4e→Re 0 . The galvanostatic electrolysis in the KF-KBF 4 -B 2 O 3 -KReO 4 melt in an atmosphere of an ambient air was performed. It was revealed that the use of the KF-KBF 4 -B 2 O 3 -KReO 4 electrolyte (with 5.4 wt% Re) provides the Re electrowinning on the Re substrate during 20 h at 773 K without a decrease in the rhenium ions concentration. The electrolytic deposits were analyzed by the XRD, SEM-EDS and ICP-AES spectroscopy. It was demonstrated that the electrolytic deposits were the metallic Re with a purity of 99.98 wt%. The operating conditions for producing the Re deposit with a current efficiency of 98% were determined.

Melting Behavior and Densities of K2B2OF6 Melts Containing KReO4

“…KF-KBF 4 -B 2 O 3 -KReO 4 melts are prospective salts for use in rhenium electrolytic reduction [21,22]. The possibility of obtaining compacted rhenium from KF-KBF 4 -B 2 O 3 -KReO 4 melts in the area of the quasi-binary K 2 B 2 OF 6 -KReO 4 melt, particularly under an air atmosphere, was demonstrated in [21,22].…”

“…KF-KBF 4 -B 2 O 3 -KReO 4 melts are prospective salts for use in rhenium electrolytic reduction [21,22]. The possibility of obtaining compacted rhenium from KF-KBF 4 -B 2 O 3 -KReO 4 melts in the area of the quasi-binary K 2 B 2 OF 6 -KReO 4 melt, particularly under an air atmosphere, was demonstrated in [21,22]. It was found that the electrolysis of KF-KBF 4 -B 2 O 3 -KReO 4 melts can be executed in an open atmosphere at temperatures up to 773 K [21].…”

A Potential-Induced Transformation in the Double Electrical Layer on the Rhenium Electrode in Alkali Chloride Melts

“…Taking into account the problems of metallurgical processing when working with refractory metals, the electrochemical deposition of compact iridium and rhenium layers, as well as alloys based on them from molten electrolytes, is widely promoted in the scientific literature. The results of these studies have shown that variation of the electrolyte composition [8][9][10][11], temperature [9][10][11][12][13][14] and current density [8,[10][11][12][13] makes it possible to obtain metallic coatings with a controlled structure, chemical and phase composition [10,[12][13][14][15][16][17], including seamless multilayer products (Ir-Re-Ir) of a desired shape [6,9]. As a rule, the electrolytic formation of products composed of refractory metals is carried out in refining baths, when a soluble anode is the source of the working metal.…”

Electrochemical Nucleation and Growth of Rhenium on Glassy Carbon in the KF-KBF4-B2O3-KReO4 Melt

“…Melts containing alkali metal fluoroborates and boron oxide are thermally stable, water-soluble, and less aggressive than fluoride melts; they have a low melting point and ability to dissolve metal oxides. [18][19][20] That is why the KF-KBF 4 -B 2 O 3 -KReO 4 melt is a perspective electrolyte for rhenium electrodeposition.…”

“…In the previous work, 18 we studied the mechanism of rhenium electroreduction on the rhenium substrate in the fluoroborate melt containing potassium perrenate and obtained the compact rhenium layers of the 99.98 wt% purity. The present work is aimed at the study of the initial stages of rhenium electrocrystallization from the KF-KBF 4 -B 2 O 3 -KReO 4 melt on the glassy carbon.…”