波长色散X射线荧光光谱法测定中低品位铝土矿和高硫铝土矿中主次组分

中低品位铝土矿种类繁多,Al₂O₃含量较低,而其他组分较为复杂,常富含Fe₂O₃、CaO、MgO、S等组分,应用熔融制样-X射线荧光光谱法(XRF)测定富含Fe₂O₃、S的样品在熔融时会腐蚀铂-金坩埚,样品流动性差,而且高温下S挥发严重。实验使用NH₄NO₃作为氧化剂,采用熔融法制样,建立了波长色散X射线荧光光谱法同时测定中低品位铝土矿和高硫铝土矿中Al₂O₃、SiO₂、Fe₂O₃、CaO、TiO₂、K₂O、Na₂O、MgO、P₂O₅、S的分析方法。为了拓宽Fe₂O₃、S等组分的含量范围,采用国家标准物质之间互相配制和经多次化学分析的样品来绘制校准曲线;通过试验确定样品与熔剂的稀释比为1∶20,加入1.0g NH₄NO₃作为氧化剂,滴加0.5mL LiBr溶液作脱模剂,在1050℃下熔样8min,可制得透彻、玻璃化程度高的样片。各组分的检出限在27.7~259μg/g之间,各组分测定结果的相对标准偏差(RSD,n=12)小于3%。经实际样品分析,各组分测定值与其他方法分析结果相吻合,有效解决了富含Fe₂O₃、S的中低品位铝土矿和高硫铝土矿的制样问题及S不易被准确测定的难题,可用于测定S质量分数15%以内的铝土矿样品。

Determination of major and minor components in medium-low grade bauxite and high-sulfur bauxite by wavelength dispersive X-ray fluorescence spectrometry

There is a great variety of medium-low grade bauxite. The content of Al₂O₃ is low and the composition of other components is complicated. It usually contains rich Fe₂O₃, CaO, MgO and S. During the determination of samples containing rich Fe₂O₃ and S by X-ray fluorescence spectrometry (XRF) after fusion sample preparation, the platinum-gold crucible can be corroded in sample melting. Moreover, the flowability of sample is poor and the volatilization of S at high temperature is serious. NH₄NO₃ was used as oxidizing agent for fusion sample preparation. The simultaneous determination method of Al₂O₃, SiO₂, Fe₂O₃, CaO, TiO₂, K₂O, Na₂O, MgO, P₂O₅ and S in medium-low grade bauxite and high-sulfur bauxite by wavelength dispersive X-ray fluorescence spectrometry was established. In order to broaden the content range of components such as Fe₂O₃ and S, the calibration curve was plotted using the national standard substances and samples after chemical analysis. The dilution ratio of sample and flux was 1∶20. In experiments, 1.0g of NH₄NO₃ was used as oxidizing agent and 0.5mL of LiBr solution was used as release agent. After fusion at 1050℃ for 8min, the transparent sample pellet with high vitrifaction degree could be prepared. The detection limits of components ranged from 27.7μg/g to 259μg/g. The relative standard deviations (RSD, n=12) of determination results were all less than 3%. The actual sample was analyzed and the found results were consistent with those obtained by other methods. The proposed study effectively solved the sample preparation problem for Fe₂O₃ and S-rich medium-low grade bauxite and high-sulfur bauxite as well as the problem that the content of S was difficult to be accurately determined. The proposed method was applicable for the analysis of bauxite samples with S content less than 15%.