氟化铵置换-EDTA络合滴定法测定三氯化钛浆液中三氯化铝

TiCl₃浆液是粗四氯化钛铝粉除V工艺中的除V试剂,其中的AlCl₃主要起催化剂作用,是影响除V试剂质量的关键因素之一。TiCl₃浆液是一种紫红色溶液,其中还含有Fe³⁺、Fe²⁺、V³⁺、V⁵⁺等有颜色的金属离子,若采用常规络合滴定法或分光光度法测量其中的AlCl₃,这些有色金属离子会产生严重干扰,无法准确判断滴定终点。实验利用氢氧化物沉淀法去除试样溶液中Ti⁴⁺、V⁵⁺、Fe³⁺等共存离子,用NH₄F置换滴定法测定试样溶液中Al。实验考察了溶液pH值对共存离子分离效果的影响,确定了滴定方式、指示剂及置换剂等实验条件。共存离子干扰试验表明,当控制测定结果相对误差不大于±2.0%时,溶液中共存离子不影响测定。方法用于测定TiCl₃浆液中AlCl₃,结果的相对标准偏差(RSD,n=8)小于3.0%;回收率为96%~102%。方法有效解决了复杂基体中Al的测定,同时也可为类似复杂基体样品其他成分分析提供参考。

Determination of AlCl3 in TiCl3 slurry by ammonium fluoride replacement-EDTA complexometric titration

TiCl₃ slurry is a vanadium removal reagent in the process of removing vanadium from crude titanium aluminum tetrachloride powder, among which AlCl₃ plays a catalytic role and is one of the key factors affecting the quality of vanadium removal reagent. TiCl₃ slurry is a kind of purplish red solution, which also contains Fe³⁺, Fe²⁺, V³⁺, V⁵⁺ and other colored metal ions. If AlCl₃ is measured by conventional complexometric titration or spectrophotometry, these non-ferrous metal ions will cause serious interference, and it is difficult to accurately judge the end point of titration. In the experiment, the co-existing ions such as Ti⁴⁺, V⁵⁺ and Fe³⁺ in the sample solution were removed by hydroxide precipitation method, and Al in the sample solution was determined by NH₄F displacement titration method. The effect of solution pH on separation results of coexisting ions was investigated. The experimental conditions including titration method, indicator and displacer were obtained. The interference tests of coexisting ions showed that the coexisting ions in solution had no influence on the determination when the relative error of measurement results was controlled within ±2.0%. The proposed method was applied for the determination of AlCl₃ in TiCl₃ slurry. The relative standard deviation (RSD, n=8) was less than 3.0%. The recoveries were between 96% and 102%. This method effectively solved the determination of Al in complex matrix. Meanwhile, it could also provide a reference for the composition analysis in other similar samples with complex matrix.