Abstract
Platinum Group Metal (PGM) concentrate is one of the output materials from the Base Metals Refinery (BMR), and the major input material for the Precious Metal Refinery (PMR). Both these refineries have an interest in knowing and understanding the full matrix i.e. all the components making up the material. This interest is due to different reasons, which range from filtration in PMR Leaching, to analytical purposes (determining the PGMs and BMs) in Base and Precious Metals Laboratories (BML/PML). In the study, concentrate samples were investigated for the concentrations of ten elements (Pt, Pd, Au, Rh, Ru, Ir, Ni, Cu, Fe and Pb) using five atomic spectroscopic techniques namely: Inductively coupled plasma – optical emission spectrometry (ICP-OES), flame atomic absorption spectroscopy (FAAS), high resolution continuum source atomic absorption spectrometry (HR-CS AAS), microwave plasma atomic emission spectrometry (MP-AES), and X-ray fluorescence spectrometry (XRF). The concentrate samples were dried and then dissolved for 24 hours under pressure using the Cl2/HCl dissolution method. Samples were further dissolved in 10% HCl for analysis by ICP-OES, HR-CS AAS, and MP-AES. For FAAS, samples were dissolved in 2.7% CuSO4 releasing reagent solution due to interferences inherent in the technique. For XRF, a sample was dried and compressed into pellets using a hydraulic Hertzog press and the elemental concentration of the prepared pellets was determined using a PanAnalytical XRF. The new techniques (HR-CS AAS, MP-AES) offered advantages over the conventional techniques in terms of analysis speed, and the suppression interferences during analysis. The five techniques gave linear calibration graphs (r2 0.999) for the ten elements (Pt, Pd, Au, Rh, Ru, Ir, Ni, Cu, Fe and Pb). Reference material (RM13) was analysed to evaluate the performance of the instrumental techniques and the accuracy and precision of the dissolution methods. The results of the reference material analysed (RM13) using the five techniques were found to be within the required ranges. Excellent overall recoveries (90-100%) were obtained for RM13 data were comparable in general for all techniques. All techniques showed very good recoveries for the precious metals, apart from XRF for Ru. Cu, Fe and Pb tended to show poorer recoveries than the precious metals for all techniques, with the exception of Pb for XRF. . Statistical analysis was conducted to evaluate accuracy and precision of the results obtained from the techniques using the certified reference material (RM13). Firstly, the Student’s t-test was used to compare the experimental means (ẋ) to the true value (μ), which showed good agreement. Two experimental means obtained with the plasma emission techniques (ICP-OES and MP-AES) and atomic absorption techniques (HR-CS AAS and FAAS) were compared with the fluorescence technique (XRF). The comparisons showed absence of significant difference in the experimental means between the two sets of results from the techniques. There was no significant difference between the experimental means obtained between the (ICP-OES and MP-AES), (HR-CS AAS and FAAS) and (ICP-OES and XRF) when using the two tailed F-test. The ANOVA was used to determine the variance among the five techniques, ANOVA showed good reproducibility, there was no variation between the results obtained from conventional newer techniques.
M.Tech. (Chemistry)