基于原位生成ZrCl4熔盐可控制备高纯锆及其合金的研究

Zirconium and its alloys are indispensable rare metal materials in nuclear industry, and the recovery of disabled and spent zirconium alloys has attracted more and more attention. In traditional electrorefining technology, there are some problems with the poor continuity and difficult introduction of zirconium electrolyte ZrCl4. To solve these problems, a continuous electrolytic refining technology of disabled and spent zirconium alloys is proposed, with a liquid alloy as anode and ZrCl4 electrolyte produced in-situ in molten salt. Liquid alloy anode is composed of disabled and spent zirconium alloy and low melting point metal M, and ZrCl4 electrolyte is produced by chlorination reaction of Zr in liquid alloy and chloride (MClx) of low melting point metal. Then continuous electrolysis recycling of disabled and spent zirconium alloy and controllable preparation of high purity zirconium and its alloys will be conducted. A rational design system and key preparation technology of liquid alloy as anode will be explored, and the dissolution of Zr, M and impurities and anodic dissolution kinetics of Zr will be investigated. The generation mechanism of ZrCl4 and its influencing factors will be explored, and the on-line monitoring of Mx+ and Zr4+ concentration will be realized by electrochemical method. The electrochemical behavior of cathodic reduction process of Mx+ and Zr4+ will be explored, and the key technology parameters of continuous preparation of pure zirconium and alloy will also be found out. A new technology of preparation of liquid alloy-electrolyte generated- preparation of pure zirconium and alloy will be formed, and a relationship law of technical parameters - composition - recovery will also be established. The aim of this research is to supply a theoretical guidance for realizing the continuous electrolytic refining of disabled and spent zirconium alloys and recycling of zirconium in nuclear industry.

核级锆及其合金作为核工业必不可少的稀有金属材料，其残、废料的精炼回收一直备受关注。针对传统精炼技术连续性差、含锆电解质ZrCl4引入困难等问题，本项目拟采用熔盐电解法，将残/废锆与低熔点金属M制成液态合金作为阳极，借助合金中Zr与低熔点金属氯化物MClx氯化反应生成ZrCl4为电解质，连续化电解回收残/废锆合金并可控制备高纯锆及其合金。探究液态合金作为阳极的合理设计制度及关键制备技术，考察Zr、M及杂质的溶出情况及Zr的阳极溶解动力学行为；探索氯化反应生成ZrCl4的机理及影响因素，借助电化学方法实现反应过程Mx+、Zr4+浓度的在线监测；探究Mx+、Zr4+阴极还原过程的电化学行为，探明连续化制备纯锆及合金的关键技术参数，形成液态合金制备-电解质生成-电解制备纯锆及合金的新技术，建立技术参数-成分-回收率的关系规律。研究成果为实现连续化精炼残/废锆以及核工业中锆的循环利用提供理论指导。

核级锆及其合金作为核工业必不可少的稀有金属材料，其残、废料的精炼回收一直备受关注。针对传统精炼技术连续性差、含锆电解质ZrCl4引入困难等问题，本项目采用熔盐法对低熔点金属M与Zr的合金阳极溶解、Zr与低熔点金属氯化物MClx氯化反应生成ZrCl4电解质、以及电解制备锆合金三个方面进行了研究，成果如下：.首先选取Cu、Sn与Zr制备液态合金阳极，研究了Cu、Sn、Zr在熔盐中的阳极溶解情况，得出了三者初始溶解电位分别为−0.51、−0.58、−1.0 V，快速溶解电位分别为−0.29、−0.37、−0.88 V。探索了Zr在Cu−Zr及Cu−Sn−Zr合金中的溶出情况，合金中Zr的溶解效果明显，在Cu−Zr合金溶解过程出现了明显的溶解过渡区和富Cu区。Zr的溶解损失量随溶解电位和溶解时间的增加均增大。溶解速率随溶解电位增加而增加，随溶解时间增长而减小；得出了锆在合金中的阳极溶解机理。.二是采用一系列电化学方法探明了Zr与氯化物MClx（CuCl、SnCl2、CuCl-SnCl2、NiCl2）的氯化反应过程中M及锆离子浓度的变化，得出M浓度在反应初始最高，随着反应进行逐步减弱至消失。而Zr的电化学信号随反应进行开始逐步增强。几种氯化反应过程获得了MClx-ZrCl4电解质与反应时间的关系规律，并最终均成功制备了ZrCl4电解质，其杂质含量在ICP检测限以下。.三是在上述制备的SnCl2-ZrCl4、NiCl2-ZrCl4及ZrCl4电解质中电沉积制备SnZr、NiZr及Zr；当Sn(Ⅱ)、Ni(Ⅱ)和Zr(Ⅳ)共存时，形成Sn3Zr5、Ni10Zr7、Ni7Zr2。当Sn(Ⅱ)浓度下降时，易形成Ni7Zr2、Ni3Sn4。SnZr合金的形状为不规则的球状及长条状，边缘类似液珠光滑圆润。以液态Sn作为阴极电沉积制备SnZr合金结果显示合金区分灰白色的富Sn区和黑色富Zr区，合金均质化还需加强研究。电沉积制备Ni-Zr合金时发现当Ni(Ⅱ)浓度较高时，制得Ni、Zr含量相差较大的Ni7Zr2、Ni10Zr7相；随着Ni(Ⅱ)浓度降低，合金相以NiZr为主。沉积所得NiZr合金相形貌为不规则的球状，沉积电压越负沉积产物颗粒尺寸越大、排列越致密。在LiCl−KCl−ZrCl4电沉积制备Zr，当电位为−1.60 V时，电解产物只有Zr，说明所有锆的氯化物已被还原为Zr单质。