Bauxite is one of the world’s sources of aluminum. Exploration, mine planning, processing and quality control require a constant monitoring of aluminum content and concentrations of other elements like silicon, iron and titanium, which are important to define the grade and value of the bauxite ore. This application note was made to evaluate the performance and rapidity of bauxite sample preparation by borate fusion followed by XRF analysis for the determination of major and minor elements.
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Bauxite is one of the world’s sources of aluminum. Exploration, mine planning, processing and quality control require a constant monitoring of aluminum content and concentrations of other elements like silicon, iron and titanium, which are important to define the grade and value of the bauxite ore. This application note was made to evaluate the performance and rapidity of bauxite sample preparation by borate fusion followed by XRF analysis for the determination of major and minor elements.
A Claisse® TheOx® Advanced fusion instrument was used to prepare the glass disks. The instrument uses electric resistance heating and has six fusion positions enabling a throughput of 24 to 30 fusions per hour. It delivers fast fusion temperature ramp up for shorter fusion cycles and an increased sample throughput.
XRF measurements were performed using a Malvern Panalytical Zetium sequential wavelength dispersive X-ray fluorescence spectrometer configured with a 2.4 kW Rh-anode Super Sharp Tube (SST R-mAX50).
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 entire cold-to-cold process took 24 minutes.
To avoid any loss of material which could lead to unprecise results, the flux was weighed directly in the 95% Pt - 5% Au crucible in which was weighed the sample. A fully automatic TheOx Advanced instrument was used to fuse the sample.
The stability of TheOx Advanced instrument has been verified by producing ten fused disks replicates on the same fusion position. This repeatability test was done using the certified reference material (CRM) NIST 698 (Table 1).
To study the inter-position repeatability of TheOx® Advanced fusion instrument during the borate fusion process, repeatability tests were done using CRM NIST 698. Two fused disks replicates were produced on each fusion position (for a total of twelve replicates).
The relative standard deviation (RDS) and average concentrations were then calculated and compared to the expected value of the CRM NIST 698 (Table 2).
| 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 | 19.60 | 0.0003 |
| ZrO2 (%) | 0.061 | 0.0660 | 0.0005 |
| 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 |
Considering that the standard deviation value includes not only sample preparation errors but also instrumental measurement errors, it can be demonstrated that TheOx Advanced instruments produces highly reproducible disks all along the six positions.
Therefore, elemental analysis with TheOx Advanced fusion instrument combined with a Zetium Minerals edition XRF spectrometer is the key to control mining, processing and quality of bauxite ores. The productivity and repeatability of TheOx Advanced instrument make fusion and the consequent benefits of an accurate XRF analysis easily achievable.
