Nickel is produced from two very different ores, lateritic and sulfidic. Lateritic ore is found primarily in tropical countries such as Indonesia and mined from various depths beneath the surface while sulfidic ore is usually found in combination with copper ore and is mined underground.
Nickel production has seen increasing demand in recent times as nickel is a key component in lithium-ion batteries, used in electric vehicles. Hence, a fast, accurate and precise method is needed for quantification of these ores both in the mining and refining processes.
X-ray fluorescence spectrometry (XRF) is a well-established analytical method to determine chemical composition in materials with high accuracy and minimum sample preparation and therefore is a preferred technique in process and quality control across many industries.
EDXRF Analysis
A convenient front-end analysis tool, EDXRF (Energy-Dispersive XRF) enables quick and easy analysis of even irregular samples with little-to-no sample preparation. In EDXRF analysis, the characteristic X-rays of different elements present in a reading are separated into a complete fluorescence energy spectrum using either direct excitation.
In EDXRF, sensitivity and precision are achieved by targeted excitation of the sample to fluoresce only the elements of interest. EDXRF technology is engineered to simultaneously process whole groups of elements for qualitative or quantitative analysis and can be used in portable and laboratory-based formats. As a result, EDXRF can accommodate samples of almost any shape and size. (Learn more.)
To test the suitability of analyzing nickel ore with EDXRF technology, we performed EDXRF analysis of nickel ore as pressed powders in an air environment. This particular EDXRF spectrometer is equipped with a Silicon Drift Detector (SDD) and a 50 Watt Rh or Ag target X-ray tube which is air cooled with a maximum excitation voltage of 50 kV.
Calibration was done using 17 nickel ore Certified Reference Materials (CRM) from OREAS®. Samples were pressed into pellets without binder at 20 tons. Two nickel ore reference materials (192 and 199) were used to validate the calibration. CRM reference values were compared with the average of 10 replicate analysis of the two CRMs.
Analysis was conducted in air. Spectra were collected on each nickel ore sample for a total live time of 5 minutes.
The analysis showed the suitability of the EDXRF spectrometer for the analysis of nickel ore samples. Accuracy and repeatability results showed that satisfactory results are obtainable for an analysis of pressed powders in air. This is a significant advantage for nickel ore mines which often operate in remote areas.
WDXRF Analysis
Wavelength Dispersive X-ray Fluorescence (WDXRF) is preferred to EDXRF for high resolution applications (~15-150 eV) and analysis of lower atomic mass elements and rare earths. Rather than process a complete spectrum, WDXRF separates fluorescent signals into individual wavelengths using crystals and a series of optical components (collimator, optical encoders, detectors, etc.).
The WDXRF Spectrometer used in the analysis does not require external or internal water cooling. Spectra were collected from each nickel ore sample for a total analysis time of 10.4 minutes at 50 W power. For sample preparation, calibration was done using 18 nickel ore CRMs. Samples were fused into beads without ignition with a sample-to-flux ratio of 1:20. Ammonium nitrate oxidizer was added to the fusion mix. Three nickel ore reference materials (181, 184, and 198) were used to validate the calibration.
The analysis showed the suitability of the specific WDXRF Spectrometer for the analysis of nickel ore samples, as it allowed for reliable and fast analysis results combined with excellent repeatability. Analysis time could be reduced with a 200 W power.
Which One is Better?
We concluded that both EDXRF and WDXRF are robust solutions in their own right, and both are suitable for analyzing nickel ore.
Editor’s Note:
For more information, including tables, analytical conditions, concentration ranges and calibration parameter values, spectra, and repeatability results, read the application notes:
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