Physico-chemical behavior of vanadium in chloride melts was studied using high temperature electronic absorption spectroscopy and spectroelectrochemistry. Dissolution of VCl3 in molten chloride leads to the formation V(III) species, VCl63-. Vanadium(II) complex ions VCl64- are formed during electroreduction of vanadium(III)-containing melts and vanadium metal anodic dissolution. V(II) chloro-species slowly react with silica to form an oxygen-containing insoluble phase. Due to high volatility of VCl4 oxygen-containing vanadyl species, VOCl42-, is the only stable form of V(IV) in fused chlorides. It is formed when V2O5, V2O4 or V2O3 react with HCl. Electroreduction of vanadyl complexes leads to the formation of insoluble oxygen-containing vanadium(III)species, whereas electrochemical oxidation has no effect on vanadium speciation, VO3+/VO2+ red-ox potential is more positive than Cl2/Cl-. Further oxidation VO2+ species gives vanadate anions. The electronic absorption spectra of soluble vanadium species were measured in 3LiCl-2KCl, NaCl-KCl and NaCl-2CsCl mixtures at 450-750 0C.
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