重量法测定镧镍合金中稀土总量

准确测定镧镍合金中稀土总量,对于有效控制镧镍合金的生产技术和产品质量具有重要意义。因镧镍合金中镍含量在50%(质量分数,下同)以上,其他共存元素中钴约10%、锰约5%,故很难通过单一分离方式彻底分离共存元素。实验依次采用氟化分离、氨水分离、草酸沉淀方式分离共存元素,进而对镧镍合金中稀土总量的测定进行探讨。试样经盐酸和硝酸溶解,采用氢氟酸、氨水、草酸沉淀稀土,逐一分离去除干扰元素,在pH值为1.8~2.0条件下,稀土元素沉淀为草酸稀土,950℃灼烧草酸稀土生成稀土氧化物(不含氧化钍),再以镧对氧化镧换算成金属稀土总量。盐酸-硝酸能够完全平稳溶解试样,且测定结果(30.42%)与参考值(30.43%)相符;采用氟化分离、氨水分离、草酸沉淀的分离方式很好地去除了镍、钴、锰、铝、铜、铁等非稀土杂质;按照实验方法测定镧镍合金样品中稀土总量,结果的相对标准偏差(RSD,n=11)均小于0.50%;加标回收率为 99%~101%。按照实验方法选取两家实验室对镧镍合金中稀土总量进行测定数据比对,结果基本一致并与参考值相符。

Determination of total rare earth content in lanthanum-nickel alloy by gravimetric method

The accurate determination of total rare earth content in lanthanum-nickel alloy has great significance for the effective control of production technology and product quality of lanthanum-nickel alloy. Since the content of nickel in lanthanum-nickel alloy was higher than 50% (mass fraction, similarly hereinafter), while the content of other coexisting elements was low (about 10% and 5% for cobalt and manganese), it was difficult to completely separate coexisting elements through a single separation method. The coexisting elements were separated by fluorine separation, ammonia separation and oxalic acid precipitation successively. Then the determination of total rare earth content in lanthanum-nickel alloy was discussed. The samples were dissolved with hydrochloric acid and nitric acid. The rare earths were precipitated using hydrofluoric acid, ammonia water and oxalic acid to separate and remove interference elements one by one. Under the condition of pH 1.8-2.0, the rare earths were precipitated into rare earth oxalates, which were then burned at 950℃ to form rare earth oxides (without thorium oxide). Finally the content of total metal rare earths was calculated by converting lanthanum to lanthanum oxide. The samples could be dissolved completely and smoothly using hydrochloric acid-nitric acid, and the determination result (30.42%) was consistent with the reference value (30.43%). The non-rare earth impurities including nickel, cobalt, manganese, aluminum, copper and iron were well removed by fluorine separation, ammonia separation and oxalic acid precipitation. Total content of rare earths in lanthanum-nickel alloy samples was determined according to the experimental method, and the relative standard deviations (RSD, n=11) were all less than 0.50%. The spiked recoveries were between 99% and 101%. Total content of rare earths in lanthanum-nickel alloy was determined in two laboratories according to the experimental method, and the results were consistent with the reference values.