Novel Extraction Of Zr Based On An In-situ Preparation Of ZrC_xO_y

A novel way was proposed in this work for zirconium extraction through ZrO₂.In this work,the feasibility of electrorefining zirconium from Zr C_xO_ysynthesized by in-situ electrolysis of ZrO₂-C composite cathode precursor as a soluble anode and the parameters of in-situ synthesis of Zr C_xO_ywere studied from the following aspects:The dissolution behavior of ZrO₂ in molten CaCl₂ and CaCl₂-CaO at different immersion times was studied respectively,and the mass changes of the samples were statistically analyzed.The phase composition,microscopic morphology and distribution of corresponding elements of the samples before and after immersion were studied by X-ray diffraction scanning electron microscopy（XRD）and X-ray energy spectrum analysis.The results show that ZrO₂has good chemical stability in molten CaCl₂,but in the presence of CaO,ZrO₂reacts with CaZrO₃to obtain the perovskite structure CaZrO₃.The anode material Zr C_xO_y was prepared by direct electrochemical reduction method.The influence of electrolytic voltage and carbon content of cathode on the synthesis of anode material with long time electrolysis,was investigated respectively.The mechanism of electrolysis synthesis of anode materials was studied by X-ray diffraction scanning electron microscopy（XRD）and X-ray energy spectrum（EDS）analysis of I-t curves,and the phase composition,the microstructure and element distribution of the electrolytic products was characterized.The results show that the corresponding current increasing with the increase of cathode voltage.Therefore,obtain a single target product will be shorter with the increase of electrolysis rate in the finally.With the decrease of carbon content of cathode,in addition to the target product Zr C_xO_y,new phase Zr₃O and the remaining intermediate product CaZrO₃which is not completely reacted appear in the product.The synthesis mechanism of Zr C_xO_y by cathodic electroreduction method was revealed through studying the phase composition,the microstructure and element distribution of the electrolytic products with different electrolysis time.It was found that in the initial stage of the electrolysis process,the ZrO₂was deoxidized to obtain ZrO_xand O^2-under the action of voltage where O^2-entered the molten salt and combined with Ca²⁺to form CaO,while ZrO_xand combined with C to form a small amount of Zr C_xO_y.Subsequently,the remaining undeoxidized ZrO₂in the cathode and CaO generate the intermediate product of perovskite structure CaZrO₃,and then CaZrO₃reacts with cathode C to obtain the anode material Zr C_xO_y.The carbon content of cathode has obvious effect on the synthesis process:The higher the content of C,the more complex the reaction process and the more diversified the intermediate products.At the initial stage of electrolysis,due to the low CaO content produced by cathode deoxidation,the intermediate products include CaZrO₃and Ca_0.2Zr_0.8O_1.8/Ca_0.15Zr_0.85O_1.85.With the increase of CaO content,all of them are converted into CaZrO₃,and then converted into the final product Zr C_xO_y.When the content of cathode C is insufficient,some of the intermediate products are directly decomposed to obtain Zr₃O,and there is a surplus of CaZrO₃due to the reduction of electrolysis rate.The electrochemical characteristics of Zr C_xO_y anode material synthesized by electrochemical reduction method were studied by means of CV,SWV,EIS and linear sweep voltammetry.The results show that Zr C_xO_ysynthesized in-situ has good anodic solubility and can be directly dissolved in molten salt as anodic material.According to CV SWV and fitting results,the reduction process of zirconium ions to zirconium in CaCl2 is(Zr⁴⁺/Zr²⁺,Zr²⁺/Zr⁺,Zr⁴⁺/Zr&Zr⁺/Zr).According to the EIS results,the electrochemical dissolution of Zr C_xO_yanode is controlled by charge transfer and ion diffusion.Zr C_xO_ywas synthesized from the compound cathode ZrO₂-C by in situ electroreduction.Then Zr C_xO_ywas used as an anode by electrorefining in molten chloride by replacing the electrode.It is found that the microstructure of the cathode product Zr is columnar dendrite by combining the results of XRD and SEM.