熔盐电解法处置镧钐渣废料制备镧钐中间合金

Preparation of Lanthanum-Samarium Master Alloy from Lanthanum Samarium Residue by Molten Salt Electrolysis

近些年来,由于金属钐的需求量递增,镧热还原生产金属钐后残余的镧钐渣处置成为难题。本文研究了镧钐渣在不同温度和时间下的焙烧产物转化过程,发现在550℃下焙烧2 h可以将镧钐渣全部转换为氧化物,满足电解原料要求。以钨电解为阴极、石墨为阳极,在3000 A电解槽中采用LiF-LaF_(3)氟盐体系电解制备LaSm中间合金。研究了电解时间、电解温度、电解质配比以及阴极电流效率等电解技术指标对电解产物杂质、电流效率以及稀土收得率之间的影响,并对电解制备得的LaSm中间合金做了表征分析。研究表明,当LaF_(3):LiF(质量比)为75:25时,电解温度为970℃,阴极电流密度为4.5~7 A·cm^(-2)工艺条件进行电解,获得的电流效率、稀土收得率最高,电解杂质含量最低。本文为镧热还原生产金属钐后残余的镧钐渣规模持续化处置提供了切实可行的解决方案,实现了镧钐渣中镧和钐的二次回收利用。

In recent years,due to the increasing demand for metal samarium,the disposal of residual lanthanum samarium residue after thermal reduction of lanthanum has become a difficult problem.In this paper,the conversion process of roasting products of lanthanum samarium slag at different temperature and time was studied.It was found that all lanthanum samarium slag can be converted into oxide at 550℃for 2 h,which can meet the requirements of electrolysis raw materials.Using tungsten electrolysis as cathode and graphite as anode,LaSm master alloy was prepared by electrolysis of LiF-LaF_(3)molten salt system in 3000 A electrolytic cell.The effects of electrolysis time,electrolysis temperature,electrolyte ratio and cathodic current efficiency on the impurities of electrolysis products,current efficiency and rare earth yield were studied,and the LaSm master alloy prepared by electrolysis was characterized and analyzed.The results show that the electrolysis temperature was 970℃and cathode current density was 4.5~7 A cm^(-2)when the LaF_(3):LiF(mass ratio)was 75:25,the current efficiency and rare earth yield are the highest and the electrolytic impurity content is the lowest.This paper provides a feasible solution for the scale continuous disposal of lanthanum samarium residue after lanthanum thermal reduction,and realizes the secondary recovery and utilization of lanthanum and samarium in lanthanum samarium slag.