Zetium - Quantification of major and minor elements in bauxite prepared as fused beads

This data sheet describes the analysis of major and minor elements present in bauxite prepared as fused beads, by X-ray fluorescence (XRF).

In order to perform the right quality process control of bauxite raw material, not only the aluminum concentration in the sample is monitored, but also concentrations of other elements like silicon (Si), iron (Fe) and titanium (Ti) which are of extreme importance. 

Zetium

Introduction

Process control of bauxite raw material not only involves monitoring the aluminium concentration in the sample but also the concentrations of other elements like silicon (Si), iron (Fe) and titanium (Ti), which are of significant importance. This data sheet describes the analysis of major and minor elements present in bauxite, by X-ray fluorescence (XRF).

Sample preparation

Calibrations were set up using seven certified reference materials (CRMs) prepared in duplicate as fused beads. The CRMs include NIST (69b, 600, 696, 697) and GBW (07177, 07181, 07182). The fused beads were prepared using a 10:1 flux (50% Li2B4O7 / 50% LiBO2) to sample ratio. The fusions were performed at a final temperature of 1150 °C using a PANalytical Eagon 2 automatic fusion machine.

Instrumentation

Measurements were performed using a Zetium XRF spectrometer, configured with a 1 kW, Rh anode, SST R X-ray tube, an X-Y sample changer and state-of-the-art SuperQ analytical software, featuring an advanced Fundamental Parameters (FP) algorithm. Zetium is engineered for excellence in terms of analytical accuracy, precision and operational performance.

Measurement conditions

The measurement times used to obtain the data, together with the compound concentration ranges, are given in Table 1. The total measurement time per sample is eight minutes, although these times can be adjusted according to the required precision.

Table 1. Measurement times (peak + background) and analytical ranges 

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Calibration results

The accuracy of the calibrations for each compound is illustrated in Table 1. The calibration RMS value is a statistical comparison (1 sigma) of the certified chemical concentrations of the standards with the concentrations calculated by regression in the calibration procedure. The lower limits of detection (LLDs) are calculated for a 100 second measurement time. Figure 1, 2 and 3 show calibration graphs for Al2O3, Fe2O3 and SiO2 respectively.

Table 2. Calibration results for given compounds in bauxite * RMS (root mean square) value is an indication of the quality of the regression. The more accurate calibrations have the smaller RMS values.

table2.PNG

Precision and instrument stability

A repeatability test was performed by measuring a standard (NIST 696) twenty times. The bead was unloaded and loaded between consecutive measurements. The results are given in Table 3. The RMS values for the repeatability measurements confirm the stability of the system. The results show good agreement between certified and average measured concentrations.

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Table 3. Repeatability results for NIST 696

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Conclusion

The results demonstrate that the Zetium spectrometer, configured with 1 kW power, is more than capable of obtaining accurate and precise compositional data for Al2O3, CaO, Cr2O3, Fe2O3, K2O, MgO, MnO, P2O5, SO3, SiO2, TiO2, ZnO and ZrO2 in bauxite prepared as fused beads in just eight minutes.

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