Rhenium Electrowinning in the KF-KBF4-B2O3-KReO4 Melt

The rhenium electrodeposition from the KF-KBF4-B2O3-KReO4 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: Re7++3e -> Re4+, and Re4++4e -> Re-0. The galvanostatic electrolysis in the KF-KBF4-B2O3-KReO4 melt in an atmosphere of an ambient air was performed. It was revealed that the use of the KF-KBF4-B2O3-KReO4 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. (C) 2018 The Electrochemical Society.