超细粉末压片制样X射线荧光光谱测定碳酸岩样品中多种元素及CO_2

Ultra-Fine Pressed Powder Pellet Sample Preparation XRF Determination of Multi-Elements and Carbon Dioxide in Carbonate

粉末压片X射线荧光光谱分析碳酸岩的误差主要来自粒度效应和矿物效应。为消除粒度效应影响,采用超细粉末压片制样准确测定了碳酸岩中的多种元素和CO2。使用德国FRITSCH行星式球磨机,碳化钨研磨介质将碳酸岩进行超细粉碎,为了克服团聚效应,采用了湿法研磨。随颗粒度的减小,样品表面形态更平整、光滑,康普顿散射效应减小。研究了粒度变化对各元素分析线强度的影响,通常荧光强度随粒度减小而增加。当多个组分的颗粒度减小时,S,Si,Mg的强度将增加,Ca,Al,Ti,K的强度将减小,这取决于各自的质量吸收系数。研究了粒度变化对矿物物相组成的影响。计算了各分析元素分析线的穿透厚度,当样品的粒度碎至元素分析线的穿透厚度以下时,荧光强度受粒度的影响减小。实验发现当样品碎至d95≤8μm时,基本消除了颗粒度效应影响,压片法制样,理论α系数、经验系数法结合校正基体效应,可准确测定碳酸岩样品中14个元素,方法的精密度大大改善,除Na2O外,RSD<2%。C是超轻元素,荧光产额低且干扰严重。实验采用PX4人工多层膜晶体,粗准直器,X射线荧光光谱可定量测定碳酸岩中的CO2。试验发现C的测量强度随测量次数的增加而增加,且随放置时间的增加而增加(即使在干燥器中存放),因此建议使用新制的样片测定CO2。

The main analysis error of pressed powder pellet of carbonate comes from particle-size effect and mineral effect.So in the article in order to eliminate the particle-size effect,the ultrafine pressed powder pellet sample preparation is used to the determination of multi-elements and carbon-dioxide in carbonate.To prepare the ultrafine powder the FRITSCH planetary Micro Mill machine and tungsten carbide media is utilized.To conquer the conglomeration during the process of grinding,the wet grinding is preferred.The surface morphology of the pellet is more smooth and neat,the Compton scatter effect is reduced with the decrease in particle size.The intensity of the spectral line is varied with the change of the particle size,generally the intensity of the spectral line is increased with the decrease in the particle size.But when the particle size of more than one component of the material is decreased,the intensity of the spectral line may increase for S,Si,Mg,or decrease for Ca,Al,Ti,K,which depend on the respective mass absorption coefficient.The change of the composition of the phase with milling is also researched.The incident depth of respective element is given from theoretical calculation.When the sample is grounded to the particle size of less than the penetration depth of all the analyte,the effect of the particle size on the intensity of the spectral line is much reduced.In the experiment,when grounded the sample to less than 8μm（d95）,the particle-size effect is much eliminated,with the correction method of theoreticalαcoefficient and the empirical coefficient,14 major,minor and trace element in the carbonate can be determined accurately.And the precision of the method is much improved with RSD2%,except Na2 O.Carbon is ultra-light element,the fluorescence yield is low and the interference is serious.With the manual multi-layer crystal PX4,coarse collimator,empirical correction,X-ray spectrometer can be used to determine the carbon dioxide in the carbonate quantitatively.The intensity of the carbon is increase with the times of the measurement and the time delay even the pellet is stored in the dessicator.So employing the latest pressed powder pellet is suggested.