紫外可见分光光度法测定磷酸三丁酯萃锂有机相中FeCl—4

直接快速测定磷酸三丁酯(TBP)/煤油有机相中以HFeCl₄·2TBP络合状态存在的铁含量,对提高盐湖卤水中锂的萃取效率、改进锂的萃取工艺具有重要的意义。先将FeCl₃·6H₂O固体溶解于不同浓度的盐酸中,采用紫外可见分光光度法测定有机相中FeCl^—₄的吸收波长,并确定其最大吸收波长为363 nm。对实验条件进行优化,结果表明,采用12 mol/L盐酸溶解FeCl₃·6H₂O时方可保证进入有机相中的铁均为FeCl^—₄。在优化条件下,制备不同浓度含FeCl^—₄的有机相标准溶液,采用紫外可见分光光度法在波长363 nm处测定吸光度,并绘制校准曲线。铁的质量浓度为0~17.8 mg/L时,吸光度与铁质量浓度呈线性相关,相关系数为0.995 6;表观摩尔吸光系数ε=1.27×10⁴L/mol;方法检出限为0.12 mg/L。按照实验方法测定TBP/煤油有机相中以FeCl^—₄存在的铁,测定结果的相对标准偏差(RSD,n=6)为0.43%~0.64%,回收率为100.10%~100.48%。

Determination of FeCl-4 in organic phase of tributyl phosphate for lithium extraction by ultraviolet-visible spectrophotometry

The direct and accurate determination of Fe content in the complex state of HFeCl₄·2TBP in the tributyl phosphate (TBP)/kerosene organic phase is of great significance for enhancing the extraction efficiency of lithium from salt lake brine and improving the extraction process. In the experiment, FeCl₃·6H₂O solid was dissolved in hydrochloric acid with different concentrations. The absorption wavelength of FeCl^-₄ in organic phase was measured by ultraviolet-visible (UV-Vis) spectrophotometry, and the maximum absorption wavelength at 363 nm was determined. The experimental conditions were optimized. The results showed that the Fe in organic phase was in the state of FeCl^-₄ when FeCl₃·6H₂O solid was dissolved with 12 mol/L hydrochloric acid. Under the optimized conditions, the standard solutions of organic phase containing FeCl^-₄ with different concentrations were prepared. The absorbance was determined by UV-Vis spectrophotometry at the wavelength of 363 nm, and the calibration curve was plotted. The absorbance was linear to the corresponding mass concentration of Fe in range of 0-17.8 mg/L. The correlation coefficient was 0.995 6. The apparent molar absorption absorptivity was ε=1.27×10⁴ L/mol. The limit of detection was 0.12 mg/L. The content of iron in the form of FeCl^-₄ in TBP/kerosene organic phase was determined according to the experimental method. The relative standard deviations (RSD, n=6) of determination results were between 0.43% and 0.64%. The spiked recoveries were between 100.10% and 100.48%.