电感耦合等离子体原子发射光谱法测定熔盐废渣中钪和钛

钒钛磁铁矿中因含量较低而不能被有效利用的Sc,在采用熔盐氯化法提取Ti时被富集于熔盐废渣中,为配合回收熔盐废渣中宝贵的Sc、Ti资源,建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定熔盐废渣中0.001%～0.5% Sc和0.25%～5.0%Ti的方法。采用HF、H₂SO₄溶解熔盐废渣,实验优化了其配比、用量和反应条件,确保样品被快速溶解完全,并且通过SiF₄挥发逸出、CaSO₄沉淀分离等方式尽量除去SiO₂、CaO等高含量基体组分,以及采用形成TiOSO₄络合物离子的方式解决高浓度Ti⁴⁺在低酸度介质下易水解的问题,从而减少样品测试溶液的酸度及其共存组分构成,有效降低基体效应等影响;重点试验了试液中共存组分的光谱干扰、连续背景叠加、基体效应等干扰因素的影响,通过优选待测元素的分析谱线及其检测积分和背景校正区域以及光谱仪工作参数等,并且采用同步背景校正法消除共存基体组分的影响。校准曲线中Sc线性范围为0.001%～0.5%,线性相关系数为0.999 6;Ti的线性范围为0.25%～5.0%,线性相关系数为0.999 2;方法检出限为0.000 01%Sc和0.000 38%Ti;元素的含量水平为0.01%～0.1%(质量分数)时结果的相对标准偏差(RSD,n=8)小于3%,含量水平为1.0%～5.0%(质量分数)时结果的相对标准偏差(RSD,n=8)小于1%;加标回收率为92%～109%。按照实验方法测定4个氯化提钛熔盐废渣样品,分别与ICP-AES测定稀土矿石中Sc(GB/T 17417.2—2010)和硫酸铁铵滴定法测定铁矿石中Ti(GB/T 6730.23—2006)进行比对,结果相一致。

Determination of scandium and titanium in molten salt slag by inductively coupled plasma atomic emission spectrometry

The content of scandium in vanadium-titanium magnetite is relatively low and cannot be effectively utilized. During the extraction of titanium by molten salt chlorination method, scandium was enriched in molten salt slag. In order to recover the valuable scandium and titanium resources in molten salt slag, the determination method of scandium (0.001%-0.5%) and titanium (0.25%-5.0%) in molten salt slag by inductively coupled plasma atomic emission spectrometry (ICP-AES) was established. The molten salt slag sample was dissolved with HF and H₂SO₄. The formula, dosage and reaction conditions were optimized in experiments to ensure the rapid and complete dissolution of sample. The matrix components such as SiO₂ and CaO with high contents were removed by SiF₄ volatilization release and CaSO₄ precipitation separation. The problem of easy hydrolysis for Ti⁴⁺ in low-acidity medium was solved by forming complex ion of TiOSO₄. The acidity of sample solution and the contents of coexisting components could be reduced, thus effectively reducing the influence of matrix effect. The influence of interference factors such as spectral interference of coexisting components, continuous background superposition and matrix effect was investigated. The detection conditions were optimized, including the analytical lines for testing elements, the integration and background correction region as well as working parameters of spectrometer. Moreover, the influence of coexisting matrix components was eliminated by synchronous background correction method. The linear range of scandium in calibration curve was 0.001%-0.5% and the linear correlation coefficient was 0.999 6. The linear range of titanium in calibration curve was 0.25%-5.0% and the linear correlation coefficient was 0.999 2. The limit of detection for scandium and titanium was 0.000 01% and 0.000 38%, respectively. When the content level of element was 0.01%-0.1% (mass fraction), the relative standard deviation (RSD, n=8) of determination results was less than 3%. When the content level was 1.0%-5.0% (mass fraction), the RSD (n=8) was less than 1%. The recoveries were between 92% and 109%. Four molten salt slag samples in titanium extraction by chlorination were determined according to the experimental method. The found results were consistent with those obtained by GB/T 17417.2-2010 (Determination of scandium in rare earth ore by ICP-AES) and GB/T 6730.23-2006 (Determination of titanium in iron ore by ammonium ferric sulfate titration method).