Direct electro-deposition of metallic chromium from K₂CrO₄ in the equimolar CaCl₂-KCl molten salt and its reduction mechanism

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• 作者：Wei Weng^a ; Mingyong Wang^b ; ^{mywang@ipe.ac.cn" class="auth_mail" title="E-mail the corresponding author} ; Xuzhong Gong^b ; Zhi Wang^b ; Dong Wang^b ; Zhancheng Guo^a
• 关键词：Electrolysis ; K2CrO4 ; Metallic chromium ; CaCr2O4 ; Molten chlorides
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：10 September 2016
• 年：2016
• 卷：212
• 期：Complete
• 页码：162-170
• 全文大小：1998 K

文摘

Spongiform metallic chromium was obtained directly from K₂CrO₄ in the equimolar CaCl₂-KCl molten salt by electrolysis at 1173 K and this reduction mechanism was discussed. The chemical composition and microstructure of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The reduction mechanism was analyzed by cyclic voltammetry, square wave voltammetry and potentiostatic electrolysis. K₂CrO₄ is soluble in the molten chlorides. The soluble CaCrO₄ was easily formed in the molten CaCl₂-KCl before electrolysis and dissociated to Ca²⁺ and CrO₄²⁻. The CrO₄²⁻ was firstly electro-reduced to CaCr₂O₄ by a three-electron-transfer process and CaO was released simultaneously. The generated CaO with a high solubility was dissolved into the CaCl₂-KCl molten salt and electro-reduced to metallic calcium. As the electrolysis proceeded, the amount of released CaO increased and more CaO was electro-reduced to Ca. CrO₄²⁻ can be reduced to CaCr₂O₄ by electrolysis and calcium reduction simultaneously. Then, CaCr₂O₄ was further reduced to metallic chromium by the dissolved Ca in the near-cathode region. However, the inclusion of a little CaCr₂O₄ brought oxygen into metallic Cr powders.