萃取分光光度法测定钴的含量

Determination of Cobalt Content by Extraction Spectrophotometry

摘要: 钴与二(2-乙基己基)磷酸酯(P₂₀₄)反应可生成蓝色的配合物。本文以该显色反应为基础，建立了一种新的测定钴含量的萃取光度分析法，并采用该方法测定了锂离子电池正极材料浸出液中钴的含量。对条件进行优化后，确定的最佳分析条件为：将皂化率为70%的P₂₀₄溶解于环己烷中，使其浓度为30 mmol/L，加入1%(v/v)磷酸三丁酯(TBP)作相改进剂，以防止第三相的形成。待测试液用0.2 moL/L pH 5.2~5.5的HAc-NaAc缓冲溶液进行稀释。将有机相与待测试液按1:1体积比混合，转速为200 r/min的条件下萃取15 min，在627 nm处测定有机相的吸光度。钴浓度在0~250 mg/L的范围内与吸光度呈良好的线性关系，线性回归方程为A = 0.0033c-0.0377, R² = 0.996。平均加标回收率为95.74% (加标回收率在94.36%~97.36%之间)，相对标准偏差为1.50% (n = 6)，表明该方法具有良好的准确度和精密度。干扰实验表明，共存的Ni、Mn对测定结果均无影响。

Abstract: Cobalt can react with bis(2-ethylhexyl) phosphate (P₂₀₄) to form blue complexes. Based on this chromogenic reaction, a new extraction spectrophotometric method for the determination of cobalt content was established. The content of cobalt in the leaching solution of cathode material of lithium ion battery was determined by this method. The operation parameters of the experiment were optimized and the optimal analysis conditions were as follows: P₂₀₄ with a saponification rate of 70% was dissolved in cyclohexane at a concentration of 30 mmol/L and 1% (v/v) of tributyl phosphate (TBP) was added as a phase modifier to prevent the formation of the third phase. The test solution was diluted with 0.2 mg/L HAc-NaAc buffer solution with a pH of 5.2 to 5.5. The organic phase was mixed with the test solution at a volume ratio of 1:1; the extraction was carried out at a rotation speed of 200 rpm for 15 minutes and the absorbance of the organic phase was measured at 627 nm. The linear regression equation was A = 0.0033c-0.0377 and R² = 0.996 in the range of 0~250 mg/L of cobalt concentration. The average recoveries were 95.74% (the recoveries ranged from 94.36% to 97.36%), and the relative standard deviation was 1.50% (n = 6), indicating that the method had good accuracy and precision. The interference experiments showed that the coexisting Ni and Mn had no effect on the determination results.