Analysis of manganese ore samples prepared as pressed pellets

Introduction

This application note shows that the Epsilon 4 - a high performance energy dispersive X-ray fluorescence spectrometer - is capable of analyzing Mn, Fe, Mg, Al, Si, P, S, Ca and Ba in manganese ore samples.

Application background

Manganese ore is an important raw material for metals industries. Manganese is a key component of stainless steel formulations and widely used aluminium alloys. Accurate elemental analysis of manganese ore samples play  a  very  important  role  in  manganese  ore mine mapping. The concentrations of Mn and Fe determine manganese ore pricing. The  presence  of  P  and  S  has  strong influence on the quality of steels and aluminium alloys. XRF analysis is a useful tool in classifying and controlling the quality of manganese ore materials.

Instrumentation

Measurements were performed using an Epsilon 4 EDXRF spectrometer, equipped with a 10W, 50 kV silver anode X-ray tube, 6 filters, a helium purge facility, a high-resolution silicon drift detector, a spinner and a 10-position removable sample changer.

Sample preparation

40 mm diameter pellets were prepared by mixing 20 g manganese ore sample material in 2 g of wax and pressed at 20 tons for 30 s. The pellet samples were put in standard sample holders and loaded into the Epsilon 4.

Measurement procedure

14 secondary manganese ore standards containing Mn, Fe, Mg, Al, Si, P, S, Ca and Ba were used to set up the calibration. The details of the conditions are given in Table 1. For P a ROI (region of interest) was used to obtain the intensities. For other elements the intensities were obtained using deconvolution. The total measurement time was 3 minutes per sample. All measurements were carried out in air atmosphere. Figures 1 and 2 show the spectra obtained for the elements in a standard.

Accurate calibration results

The calibration plots shown in Figures 3 and 4 demonstrate the strong correlation between the given concentrations and the measured intensities. The accuracies of the method calibrations are illustrated by the consistently low RMS values (Table 2).

Table 1. Measurement conditions

Figure 1. The spectrum of a standard obtained with 5 kV , showing the excellent resolution and the high sensitivity of the detector

Figure 2. The spectrum of a standard obtained with 20 kV and Al thick filter

Figure 3. Calibration graph of Mn

The excellent calibration accuracies can be partially ascribed to the fact that the in-house standards used have a similar origin and mineralogy. This reduces the influence of so-called mineralogical effects that are commonly seen in pressed powder calibrations of certified reference materials that may have diverse mineralogies. The LLD values presented in Table 2 are calculated using the application measurement time.

Figure 4. Calibration graph of Fe

Precision

An indication of the measurement precision was obtained by analysing a sample repeatedly (n=20). The averages and the standard deviations (1 sigma) are presented in Table 3.

Table 2. The RMS values of the calibration

Table 3. Results of the repeatability test

Conclusions

The data presented here clearly demonstrates the suitability of the Epsilon 4 EDXRF spectrometer for the quantitative analysis of Mn, Fe, P, S, MgO, Al2O3, SiO2, CaO and BaO in manganese ore samples. Accurate and precise results can be obtained in just 3 minutes.