Zetium Minerals edition
Bauxite is the primary ore for the production of alumina, which is in turn used in the electrolytic smelting process to produce aluminium. It forms from in-situ chemical weathering in tropical to sub-tropical climates, e.g. Australia. Bauxite is composed primarily of one or more aluminum hydroxide minerals, plus various mixtures of silica, iron oxide, titanium oxide, aluminum silicates, and other impurities in minor or trace amounts. This data sheet demonstrates the performance of the Minerals edition of the Zetium XRF spectrometer in providing accurate and precise bauxite analyses.
The Minerals edition of the Zetium spectrometer is a fully integrated wavelength dispersive XRF spectrometer, complete with X-Y sample handler and state-of-the-art software. Engineered for excellence in terms of both analytical and operational performance, it has been configured specifically to meet the needs of users in the mining and minerals industries.
The Minerals edition of the Zetium spectrometer can be delivered with a set of 19 synthetic multi-element wide- range oxides (WROXI) standards and an application template for the analysis of major and minor oxides in fused beads. Using Malvern Panalytical’s unique FP algorithm implemented in our SuperQ analytical software, the WROXI application can determine concentrations of up to 21 common oxides in a wide range of rocks, ores and minerals. WROXI calibrations can be used directly when routine samples are fused but they can also be used to certify in-house standards to be used to create pressed powder calibrations, decreasing the average cost and time of analysis.
Figure 1. Comparison of certified and measured values for bauxite and bauxite-related samples
Sample preparation and measurement details
Nine certified reference materials (CRMs), consisting of 5 NIST and 2 BCS bauxites, an iron ore (ECRM-681-1) and a lateritic soil (GSS-7), were prepared and analyzed as routine samples to test the accuracy of the WROXI calibrations. The WROXI standards and CRMs used in this study were prepared using 0.9 g of sample fused in 9.0 g flux (66 % lithium tetraborate, 34 % lithium metaborate) and cast into 40 mm diameter fused beads.
The measurement program used to obtain the data presented in this data sheet had a total measurement time of nine minutes (Table 1). Times can, however, be adjusted according to the required precision.
The precision, repeatability and reproducibility of the Zetium spectrometer are excellent, not only over the short term, but also for a longer 14 day period (Table 3). The data presented in Table 3 did not require any form of drift correction. For comparison, the counting statistical error (CSE) expressed in concentration units is also shown in Table 3. The CSE is theoretically the minimum possible error and the data demonstrate the inherent stability of the Zetium spectrometer.
Table 1. Total measurement time (peak + background)
The accuracy of the Zetium spectrometer, using WROXI standards and the SuperQ (FP) calibration model for major and minor element analyses in bauxite and related materials is very good. This is illustrated in Figure 1 for individual oxides; Al2O3, SiO2 and Fe2O3 for the all the analyzed bauxite CRMs, and in a comparison of certified and measured values for 15 oxides in a bauxite CRM (NIST SRM-697) in Table 2.
Table 2. A comparison of certified and measured concentrations for abauxite NIST SRM-697
Table 3. Reproducibility (10 measurements over 14 days) for bauxite (NIST SRM-697)
Elemental analysis with XRF is already the key to quality and production control in industries analysing a wide range of oxide materials. The Minerals edition of the Zetium spectrometer, in combination with WROXI and the FP algorithm within SuperQ, represents an ideal solution for the analysis of bauxite. It has been demonstrated that the analyses are accurate and precise and the method benefits from a simple fusion sample preparation. Furthermore, the stability of the system is such that individual calibrations can be used for months. Time-consuming recalibrations are, therefore, unnecessary and the resultant data are highly consistent over time.