Using Bauxite Type Samples Followed by XRF Analysis for an Inter-Position Repeatability Study with TheOx® Advanced Instrument

Image Credits: shutterstock.com/electra

Image Credits: shutterstock.com/electra

One of the major sources of aluminum in the world is bauxite. Aluminum content and concentrations of other elements such as iron, silicon, and titanium need to be continuously monitored during mine planning, exploration, processing, and quality control as these values are critical to define the value and grade of the bauxite ore. This article evaluates the performance and rapidity of bauxite sample preparation process involving borate fusion and subsequent XRF analysis to determine major and minor elements.

The glass disks were prepared using a Claisse® TheOx® Advanced fusion instrument. The instrument employs electric resistance heating and consists of six fusion positions, providing a throughput of 24 to 30 fusions per hour. It not only delivers an increased sample throughput, but also provides fast fusion temperature ramp up for shorter fusion cycles.

A PANalytical Zetium sequential wavelength dispersive X-ray fluorescence spectrometer equipped with a 2.4 kW Rh-anode Super Sharp Tube (SST R-mAX50) was used to perform XRF measurements.

Global Sample Preparation Method

All samples were prepared using a 1:10 dilution ratio with a LiT/LiM 50/50 flux, pure grade (99.98+%) without non-wetting agents. The time taken for the entire cold-to-cold process was 24 minutes. The flux was weighed directly in the same 95% Pt - 5% Au crucible, wherein the sample was weighed to prevent any material loss which could cause inaccurate results. The sample was fused using a fully automatic TheOx Advanced instrument.

Challenges

  • Rapid and accurate sample preparation and sample analysis are required to control exploration, mining and processing of the mineral
  • High reproducibility and inter-position repeatability for robust and stable sample preparation

Benefits

  • Simple and fast
  • High throughput
  • Inter-position repeatability and stability
  • Precise results

Results

Ten fused disks replicates were prepared on the same fusion position in order to verify the stability of TheOx Advanced instrument. This repeatability test was carried out using the certified reference material (CRM) NIST 698 (Table 1).

Table 1. Results of the sample preparation repeatability test for CRM NIST 698 where 10 fused disk replicates were produced on the same fusion position

NIST 698 Certified value (wt%) Average value (wt%) RSD (wt%)
Na2O (%) 0.015 0.017 0.001
MgO (%) 0.058 0.052 0.001
Al2O3 (%) 48.2 48.30 0.03
SiO2 (%) 0.69 0.680 0.007
P2O5 (%) 0.37 0.380 0.001
SO3 (%) 0.143 0.145 0.002
K2O (%) 0.01 0.0100 0.0009
CaO (%) 0.62 0.570 0.003
TiO2 (%) 2.38 2.320 0.005
V2O5 (%) 0.064 0.068 0.001
Cr2O3 (%) 0.08 0.0800 0.0006
MnO (%) 0.383 0.3840 0.0008
Fe2O3 (%) 19.6 19.60 0.02
ZnO (%) 0.029 0.0280 0.0003
ZrO2 (%) 0.061 0.0660 0.0005

Repeatability tests were performed using CRM NIST 698 to examine the inter-position repeatability of the TheOx® Advanced fusion instrument during the borate fusion process. For a total of twelve replicates, two fused disks replicates were prepared on each fusion position. Then, the average concentrations and relative standard deviation (RDS) were calculated and compared with the expected value of the CRM NIST 698 (Table 2).

Table 2. Results of the sample preparation repeatability test for CRM NIST 698 where two fused disk replicates were produced on each fusion position – for a total of 12 replicates

NIST698 Certified value (wt%) Average value (wt%) RSD (wt%)
Na2O (%) 0.015 0.017 0.001
MgO (%) 0.058 0.051 0.001
Al2O3 (%) 48.2 48.31 0.02
SiO2 (%) 0.69 0.675 0.008
P2O5 (%) 0.37 0.383 0.002
SO3 (%) 0.143 0.144 0.002
K2O (%) 0.01 0.011 0.001
CaO (%) 0.62 0.567 0.003
TiO2 (%) 2.38 2.321 0.006
V2O5 (%) 0.064 0.066 0.002
Cr2O3 (%) 0.08 0.079 0.001
MnO (%) 0.383 0.385 0.001
Fe2O3 (%) 19.6 19.60 0.01
ZnO (%) 0.029 0.0280 0.0003
ZrO2 (%) 0.061 0.0660 0.0008

Conclusion

Considering that sample preparation errors as well as instrumental measurement errors are included in the standard deviation value, it can be shown that highly reproducible disks are produced all along the six positions by the TheOx Advanced instrument.

Hence, elemental analysis using the combination of the TheOx Advanced fusion instrument and a Zetium Minerals edition XRF spectrometer is an effective method to control mining, processing, and quality of bauxite ores. The results confirm that fusion and the consequent benefits of an accurate XRF analysis can be easily achieved, thanks to the productivity and repeatability of the TheOx Advanced instrument.

This information has been sourced, reviewed and adapted from materials provided by Claisse.

For more information on this source, please visit Claisse.

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