How to Test for Nickel Ore in an Air Environment

Nickel is created from two very distinct ores, sulfidic and lateritic. Sulfidic ore is normally found alongside copper ore and is mined underground, while lateritic ore is mostly located in tropical countries like Indonesia and mined from a range of depths underneath the surface.

The production of nickel has seen a rise in demand in recent times because nickel is the main element of lithium-ion batteries employed in electric vehicles. As such, a precise, efficient and accurate technique is required for the measurement of these ores in both the refining and mining processes.

X-Ray fluorescence spectrometry (XRF) is a well-reputed analytical technique to establish chemical composition in materials with minimal sample preparation and high accuracy. This makes it a popular quality and process control method in several industries.

Instrumentation

The Thermo Scientific™ ARL™ QUANT’X EDXRF Spectrometer features a Silicon Drift Detector (SDD) and a 50 watt Rh or Ag target X-Ray tube, which is air cooled with a 50 kV maximum excitation voltage.

A set of nine primary beam filters is engineered to enhance the peak-to-background signals for all elements from F to Am. Autonomous analysis of multiple samples is made possible by the 10-position auto-sampler with spinner.

Its SDD continues to be the benchmark of performance for all energy-dispersive detectors. The substantial active area of 30 mm² allows characteristic element X-Rays released by the sample to be successfully captured.

Excitation Conditions

In EDXRF, precision and sensitivity are attained through the targeted excitation of the sample to fluoresce only the elements of interest. The ARL QUANT’X EDXRF Spectrometer provides several primary beam filters for ideal background control and a nearly endless combination of excitation voltages (4-50 kV).

For a total live time of 5 minutes, spectra were acquired on each nickel ore sample, as demonstrated in Table 1. Based on the specific application, the measurement time can be further adjusted. The analysis is performed in air.

Table 1. Analytical conditions. Source: Thermo Fisher Scientific – Materials & Structural Analysis

Condition Voltage Tube Filter Medium Live Time (s) Elements
Low Za 4 No Filter Air 180 Mg, Al, Si
Low Zb 8 C Thick Air 60 S, Ca, K
Mid Za 16 Ag Thin Air 60 Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn

 

Sample Preparation

Calibration was performed utilizing 17 nickel ore Certified Reference Materials (CRM) from OREAS®. Samples were pressed into pellets without binder at 20 tons.

Table 2 presents the concentration ranges of the various oxides measured by the calibration along with the RMSE (root mean square error) and R² values acquired for the various compounds.

Table 2. Concentration ranges and calibration parameter values for the analysis of nickel ore. Source: Thermo Fisher Scientific – Materials & Structural Analysis

Element Min % Max % R2 RMSE
MgO 0.7 27.3 0.9986 0.4
Al2O3 1.6 17.5 0.9985 0.2
SiO2 22.8 48.0 0.9896 0.8
SO3 0.03 0.19 0.9897 0.007
K2O 0.069 0.228 0.9935 0.006
CaO 0.13 3.11 0.9995 0.019
TiO2 0.02 1.36 0.9998 0.003
Cr2O2 0.17 1.75 0.9971 0.02
MnO 0.11 1.94 0.9997 0.008
Fe2O2 12.7 46.0 0.9986 0.4
Co 0.023 0.090 0.9839 0.003
Ni 0.05 2.94 0.9993 0.02
Cu 0.007 0.05 0.9999 0.00014
Zn 0.007 0.035 0.9968 0.0005

 

Calibration

By relating the element’s characteristic X-Ray intensity to oxide concentration, calibration curves have been attained. X-Ray fluorescence quantifies elements, but the results can be directly attributed to the oxide forms of these elements when only one distinct type of oxide is found in the sample.

Figures 1 to 14 demonstrate the calculated versus given concentration plots acquired for MgO, Ni, SiO₂, Al₂O₃, K₂O, SO₃, TiO₂, CaO, MnO, Cr₂O₃, Co, Fe₂O₃, Zn and Cu.

Ni Calculated versus Given Concentrations.

Figure 1. Ni Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

MgO Calculated versus Given Concentrations

Figure 2. MgO Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Al2O3 Calculated versus Given Concentrations.

Figure 3. Al2O3 Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

SiO2 Calculated versus Given Concentrations.

Figure 4. SiO2 Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

SO3 Calculated versus Given Concentrations.

Figure 5. SO3 Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

K2O Calculated versus Given Concentrations.

Figure 6. K2O Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

CaO Calculated versus Given Concentrations.

Figure 7. CaO Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

TiO2 Calculated versus Given Concentrations.

Figure 8. TiO2 Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Cr2O3 Calculated versus Given Concentrations

Figure 9. Cr2O3 Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

MnO Calculated versus Given Concentrations.

Figure 10. MnO Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Fe2O3 Calculated versus Given Concentrations

Figure 11. Fe2O3 Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Co Calculated versus Given Concentrations

Figure 12. Co Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Cu Calculated versus Given Concentrations

Figure 13. Cu Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Zn Calculated versus Given Concentrations

Figure 14. Zn Calculated versus Given Concentrations. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis

Validation

To validate the calibration, two nickel ore reference materials (192 and 199) were used. Table 3 presents the results of the analysis for these reference materials.

Table 3. Accuracy of results for standards 192 and 199 using ARL QUANT’X Spectrometer. Source: Thermo Fisher Scientific – Materials & Structural Analysis

  MgO % Al2O3 % SiO2 % SO3 % K2O % CaO % TiO2 % Cr2O3 % MnO % Fe2O3 % Co % Ni % Cu % Zn %
192 Reference 21.32 2.76 43.58 - - 0.313 0.036 0.9129 0.277 18.1 0.0404 1.77 - 0.0176
192 Analysis 21.86 2.61 43.97 0.03 0.0104 0.308 0.034 0.8854 0.269 18.2 0.0376 1.80 0.0060 0.0164
199 Reference 0.742 17.47 24.93 0.08 0.069 0.208 0.842 0.686 1.94 41.01 0.0554 0.0995 0.0189 0.0198
199 Analysis 0.880 17.94 24.58 0.07 0.0724 0.213 0.840 0.695 1.95 40.68 0.0566 0.0984 0.0189 0.0206

 

CRM reference values are compared with the average of 10 replicate analyses of the two CRMs, whereas Tables 4a and 4b present the repeatability results for each CRM.

Table 4a. Repeatability results for standards 192 using ARL QUANT’X Spectrometer. Source: Thermo Fisher Scientific – Materials & Structural Analysis

  MgO % Al2O3 % SiO2 % SO3 % K2O % CaO % TiO2 % Cr2O3 % MnO % Fe2O3 % Co % Ni % Cu % Zn %
Repeats 01 21.853 2.574 44.171 0.032 0.0104 0.307 0.034 0.885 0.269 18.187 0.036 1.803 0.0060 0.0164
Repeats 02 21.992 2.565 43.843 0.031 0.0104 0.309 0.032 0.882 0.266 18.175 0.038 1.803 0.0060 0.0158
Repeats 03 21.785 2.633 44.018 0.032 0.0104 0.307 0.034 0.886 0.268 18.174 0.039 1.802 0.0060 0.0164
Repeats 04 21.843 2.625 43.916 0.029 0.0104 0.308 0.033 0.886 0.270 18.202 0.037 1.800 0.0060 0.0164
Repeats 05 21.448 2.712 44.334 0.033 0.0104 0.308 0.038 0.886 0.270 18.209 0.036 1.807 0.0060 0.0167
Repeats 06 21.950 2.589 43.882 0.032 0.0104 0.307 0.034 0.888 0.268 18.188 0.037 1.800 0.0060 0.0162
Repeats 07 21.901 2.607 43.973 0.030 0.0104 0.307 0.030 0.886 0.270 18.173 0.039 1.804 0.0060 0.0167
Repeats 08 21.958 2.586 43.913 0.028 0.0104 0.306 0.034 0.886 0.270 18.199 0.038 1.803 0.0060 0.0165
Repeats 09 21.950 2.626 43.707 0.031 0.0104 0.308 0.038 0.888 0.269 18.185 0.038 1.802 0.0060 0.0163
Repeats 10 21.964 2.581 43.964 0.030 0.0104 0.310 0.035 0.882 0.271 18.198 0.040 1.804 0.0060 0.0166
Average 21.864 2.610 43.972 0.031 0.0104 0.308 0.034 0.885 0.269 18.189 0.038 1.803 0.0060 0.0164
1-Sigma 0.160 0.043 0.175 0.002 - 0.001 0.002 0.002 0.001 0.013 0.001 0.002 - 0.0003
% RSD 0.73 1.65 0.40 4.86 - 0.32 6.95 0.23 0.51 0.07 3.34 0.12 - 1.62
Minimum 21.448 2.565 43.707 0.028 0.0104 0.306 0.030 0.882 0.266 18.173 0.036 1.800 0.0060 0.0158
Maximum 21.992 2.712 44.334 0.033 0.0104 0.310 0.038 0.888 0.271 18.209 0.040 1.807 0.0060 0.0167

 

Table 4b. Repeatability results for standards 199 using ARL QUANT’X Spectrometer. Source: Thermo Fisher Scientific – Materials & Structural Analysis

  MgO % Al2O3 % SiO2 % SO3 % K2O % CaO % TiO2 % Cr2O3 % MnO % Fe2O3 % Co % Ni % Cu % Zn %
Repeats 01 1.009 17.750 24.609 0.069 0.074 0.213 0.845 0.696 1.943 40.653 0.056 0.098 0.0191 0.0212
Repeats 02 1.053 17.755 24.563 0.073 0.071 0.213 0.839 0.693 1.945 40.680 0.058 0.099 0.0192 0.0205
Repeats 03 0.981 17.827 24.559 0.077 0.073 0.215 0.847 0.694 1.942 40.698 0.056 0.098 0.0190 0.0209
Repeats 04 0.773 18.055 24.612 0.074 0.073 0.213 0.838 0.694 1.950 40.683 0.057 0.099 0.0186 0.0208
Repeats 05 0.887 17.903 24.685 0.074 0.073 0.214 0.841 0.690 1.950 40.651 0.058 0.098 0.0189 0.0208
Repeats 06 1.203 17.767 24.359 0.073 0.071 0.213 0.838 0.697 1.940 40.669 0.055 0.098 0.0188 0.0196
Repeats 07 1.024 17.885 24.488 0.078 0.074 0.211 0.848 0.690 1.939 40.656 0.057 0.098 0.0190 0.0209
Repeats 08 0.389 18.263 24.756 0.074 0.073 0.213 0.836 0.698 1.953 40.693 0.058 0.099 0.0188 0.0202
Repeats 09 0.746 18.160 24.516 0.076 0.072 0.215 0.835 0.699 1.941 40.687 0.055 0.099 0.0190 0.0210
Repeats 10 0.737 18.040 24.614 0.075 0.071 0.213 0.836 0.695 1.948 40.688 0.058 0.098 0.0186 0.0204
Average 0.880 17.941 24.576 0.074 0.072 0.213 0.840 0.695 1.945 40.676 0.057 0.098 0.0189 0.0206
1-Sigma 0.229 0.181 0.109 0.002 0.001 0.001 0.005 0.003 0.005 0.017 0.001 0.001 0.0002 0.0005
% RSD 26.03 1.01 0.44 3.28 1.56 0.49 0.56 0.43 0.25 0.04 2.29 0.62 1.06 2.27
Minimum 0.389 17.750 24.359 0.069 0.071 0.211 0.835 0.690 1.939 40.651 0.055 0.098 0.0186 0.0196
Maximum 1.203 18.263 24.756 0.078 0.074 0.215 0.848 0.699 1.953 40.698 0.058 0.099 0.0192 0.0212

 

Conclusion

This article demonstrates the ARL QUANT’X EDXRF spectrometer’s suitability for the investigation of nickel ore samples. This compact instrument enables nickel ores to be analyzed quickly and reliably.

Repeatability and accuracy results confirm that correct results can be achieved when analyzing pressed powders in air. This is a major benefit for nickel ore mines which frequently operate in remote locations.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific – Materials & Structural Analysis.

For more information on this source, please visit Thermo Fisher Scientific – Materials & Structural Analysis.

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