难熔金属含氧酸盐直接电解与碱转化再生应用基础

Long processes, high energy consumption and severe pollution are the issues for traditional metallurgy of refractory metals. A novel method that refractory metal oxysalts in melting state (such as NaxMOy) are electrolyzed directly and alkali is also regenerated at the same time is suggested. However, it is difficult to seek molten salts with high solubility for electrolytic reactants. In this item, refractory metal oxysalts are used as both electrolytic reactants and conductive molten salts due to low melting point and ionization. Based on the analysis of physicochemical properties of molten salts and decomposition thermodynamics, new system which is suitable to electrolyze refractory metal oxysalts is builded. The electrochemical reduction mechanism of refractory metal oxyacid root with negative charges is analyzed. Electrode process kinetics of refractory metal oxyacid root in cathode and intensified methods are studied. According to the adjustment of anodic reaction and molten salt properties, reaction thermodynamics and kinetics that Na+ and O2- are converted into Na2CO3 for alkali regeneration are elucidated. The relationships between electrolytic conditions, molten salt properties and the separation of Na2CO3 from molten salts are investigated. Furthermore, the methods to control electrolytic process of refractory metal oxysalts are obtained in order to achieve the matching of metal electrolysis and alkali regeneration. The results in this item will provide theoretical foundation for building universal and green method to produce refractory metals with high efficiency.

针对难熔金属传统冶金流程长、能耗高和污染重的问题，提出难熔金属含氧酸盐中间体（如NaxMOy）直接熔盐电解与碱（Na+和O2-）转化再生的短流程新方法。为克服传统熔盐电解存在的电解原料在熔盐中溶解度低的难题，新方法直接以熔点低、可电离的难熔金属含氧酸盐为电解反应物和导电熔盐。基于金属含氧酸盐和熔盐添加组分物化性质与分解热力学分析，建立适于难熔金属含氧酸盐直接电解的熔盐电解新体系；重点解析负电性含氧酸根离子电化学还原反应机理，研究金属含氧酸盐直接电解电极反应动力学规律与强化机制；基于阳极反应过程和熔盐物性调节，研究钠离子和氧离子向Na2CO3再生转化的平衡热力学和动力学行为；探明电解工艺和熔盐性质与Na2CO3定向分离的关联关系和控制制度；在此基础上，掌握难熔金属含氧酸盐电解过程调控方法，实现金属电解和碱再生的协同匹配。本项目的实施将为建立难熔金属清洁、高效转化新方法奠定基础。

难熔金属是一类在航空航天、原子能等高精尖领域具有广泛应用的高熔点金属。针对现有难熔金属（如钒、铬、钛等）冶金过程物质形态反复转化导致的流程长、能耗高和污染重的问题，本项目提出了可溶性难熔金属含氧酸盐中间体直接熔盐电解金属（SOSE）与碱转化再生短流程新方法。围绕高价态、多变价金属可控还原动力学机制与过程强化的科学问题，分析了钒/铬/钛金属含氧酸盐在氯化物或氟化物熔盐中的溶解行为和赋存结构，热力学计算发现金属含氧酸盐分解电压远低于常见氯化物或氟化物熔盐，含氧酸盐直接电解金属具有热力学可行性，建立了适于可溶性难熔金属含氧酸盐电解的熔盐体系；掌握了氯化物熔盐体系高价态-多变价钒/铬含氧酸盐还原度可控调节规律，实现了较高纯度低价金属氧化物和金属的制备，解析了高价态钒/铬化学-电化学梯级还原机理，探明了铬酸盐电解过程电流效率与碳氧杂质变化规律，揭示了电流效率损耗和碳污染根源，提出电极结构优化强化铬酸盐电解与同步抑制碳污染新方法，电流效率可达85%以上；提出了钒/铬含氧酸盐电解过程碱循环再生技术路线；研究了氟盐体系可溶性钛酸钙电化学还原产物价态和物相的变化历程，解析了高价态钛多步还原机理，掌握了钛粉和氟盐高温蒸发分离方法。本项目研究成果将为钒钛磁铁矿中钒/铬/钛金属的短流程、清洁提取奠定理论基础和技术支撑。本项目总计发表SCI论文13篇（总IF 42.106），国内外学术会议论文/口头报告7次，获优秀墙报奖1次，申请发明专利2项（其中授权1项），负责人入选中科院青年创新促进会会员，培养博士生2名，硕士生3名。