乙酸丁酯萃取-EDTA滴定法测定铟阳极泥中高含量铟

铟阳极泥中除了含有大量铟外,还含有一定量的铅、锌、铜、锡、铋、锑等,如果直接应用EDTA滴定法对铟阳极泥中铟进行测定,这些杂质元素将会对测定产生干扰,据此,实验提出了采用盐酸、硝酸、氢溴酸-硫酸分解试样,在碘化钾-硫酸介质中使I-与In3+络合从而以InI4-形式被乙酸丁酯萃取,用2%(V∶V)盐酸再反萃取两次,最终用EDTA滴定法测定铟阳极泥中铟的分析方法。条件优化实验表明:在1.5mol/L KI-2.0mol/L H2SO4介质中,用20mL乙酸丁酯对30mg铟的萃取率基本达100%;用50mL 2%盐酸、20mL 2%盐酸对15.00mL 2g/L铟标准溶液各反萃取一次,铟的反萃取率基本达100%;在pH 2.5~3.0及微沸条件下,用EDTA标准滴定溶液滴定,滴定终点清晰明亮,突跃明显,结果平稳。将实验方法应用于铟阳极泥中铟的测定,铟的回收率为99%~101%,测得结果的相对标准偏差(RSD,n=6)小于1%。

Determination of high content indium in indium anode slime by butyl acetate extraction-EDTA titration

Apart from much indium, the indium anode slime also contains lead, zinc, copper, tin, bismuth and antimony. These impurity elements will cause interference when the content of indium in indium anode slime was directly determined by EDTA titration.The sample was decomposed by hydrochloric acid, nitric acid, hydrobromic acid-sulfuric acid. In³⁺ was then complexed with I^－ in potassium iodide-sulfuric acid medium to form InI₄^－, which could be extracted with butyl acetate. After reextraction with 2% (V∶V) hydrochloric acid twice, the content of indium in indium anode slime was finally analyzed by EDTA titration. The experimental results under optimized conditions indicated that the extraction rate for 30 mg of indium by 20 mL of butyl acetate in 1.5 mol/L KI-2.0 mol/L H₂SO₄ medium was almost 100%. Then, 15.00 mL of 2 g/L indium standard solution was re-extracted by 50 mL of 2% hydrochloric acid and 20 mL of 2% hydrochloric acid, respectively, and the reextraction rate was almost 100%. The titration was conducted using EDTA standard solution at pH 2.5-3.0 and slight boiling state .The endpoint was clear and bright with obvious abrupt change. The determination results were smooth. The proposed method was applied to the determination of indium in indium anode slime. The recoveries of indium were between 99% and 101%. The relative standard deviation (RSD, n=6) was less than 1%.