Using the Empirical Method for Elemental Analysis of Barite Ore

Elemental analysis plays a key role in different stages of mining material production in order to ensure proper extraction and process control. Trace elemental analysis, particularly for precious metals, is highly significant to ensure process optimization. Hence, there is a requirement for a simple but robust technique throughout the entire processing line.

The ideal solution to address these industry challenges is the NEX QC energy dispersive X-ray fluorescence (EDXRF) elemental analyzer from Rigaku. The NEX QC analyzer combines a high-performance semiconductor detector and 50 kV direct excitation to deliver unprecedented sensitivity and lower detection limits. It is a robust, yet simple, and affordable instrument to perform elemental analysis of ores and rocks. This article demonstrates the ability of the NEX QC analyzer to measure silver (Ag), lead (Pb), zinc (Zn), and iron (Fe) in barite (BaSO₄) concentrates and final tails, using the empirical method.

The Rigaku NEX QC EDXRF Analyzer

Experimental Setup

• Model: Rigaku NEX QC
• Detector: Semiconductor
• X-ray tube: 50 kV 4 W Ag-anode
• Sample Type: Ore powders
• Film: Mylar
• Environment: Air
• Analysis Time: 300 seconds
• Options: Manual Sample Press
• Optional: 6-position 32mm Autosampler

Sample Preparation

Samples were prepared by grinding the ore material to a homogeneous dry powder of <200 mesh (<75µm particle size), followed by transferring and manually compacting 10 g of the powder into a standard 32 mm sample cup by applying 250 inch-pounds of torque through the manual sample press in order to ensure uniform compaction.

Calibration and Measurement

Individual empirical calibrations were built for each of the supplied matrix types (concentrates and final tails). Empirical calibrations for each main element in the sample matrix were developed utilizing 17 assayed concentrate samples and 20 final tails. The variations in X-ray absorption and enhancement effects within the sample caused by the independent variations in elemental concentration were then automatically compensated by employing ‘alpha corrections.’

Generally, assaying of samples is performed at the mine and processing sites. The assayed samples are then chosen as standards for each element in order to ensure a wide, representative range in concentration. Each suite of standards also incorporates many different samples that differ independently in elemental concentration so as to provide a highly precise model of the ore matrix. The summaries of calibration curves are listed below:

Table 1. Concentrates

Table 2. Final Tails

Concentrates Ag correlation plot and Final tails Ag correlation plot are shown below:

Table 3. Concentrates Ag Correlation Plot

Table 4. Final Tails Ag Correlation Plot

Recovery and Repeatability

A concentrated sample and a final tail sample were chosen from the silver concentration mid-range and repeatedly analyzed in a static position for 10 times in order to show recovery and repeatability (precision). The results of the analyses are listed below:

Table 5. Concentrates

Table 6. Final Tails

Empirical Detection Limits (LLD)

The empirical approach was employed for determining detection limits in a ’blank’ matrix. The approach involved the 10 repeat analyses of CaO powder to model the X-ray properties of ore. The measurement of the sample was taken in a static position and the standard deviations were calculated. Then, the lower limit of detection (LLD) was defined as three times the standard deviation. The LLDs for the elements, Ag, Fe, Zn and Pb, are shown below:

Table 7. Concentrates

Table 8. Final Tails

Conclusion

The results clearly demonstrate the ability of the Rigaku NEX QC EDXRF analyzer to monitor and quantify silver as well as other major and minor elements present in mining and ore materials rapidly and accurately. The system is capable of measuring elements from sodium and uranium. This capability will enable the system to adapt when existing processes are optimized and new processes are launched.

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

For more information on this source, please visit Rigaku Corporation.