Michael Rampfumedzi, Tshilidzi2024-10-242024-10-242024Michael Rampfumedzi, Tshilidzi . (2024). Characterization, quantification, and recovery of rare earth elements(rees) in South African coal fly ash samples [Master’s dissertation, University of the Witwatersrand, Johannesburg]. WireDSpace.https://hdl.handle.net/10539/41915https://hdl.handle.net/10539/41915A Master's dissertation submitted to the University of the Witwatersrand in fulfillment with the requirements of the degree of Master of Science, Johannesburg 2024Rare earth elements (REEs) are naturally distributed throughout the Earth's crust, typically in low concentrations. They are not typically found in isolation but are rather present in various minerals, often in amounts too minute for cost-effective extraction. Fly ash is among the sources that are deemed economically viable for extracting REEs. The objective of this study was to create environmentally sustainable approaches for measuring and reclaiming rare earth elements (REEs) in coal fly ash (CAF) samples. The study involved analyzing fly ash samples collected from various coal power stations using a range of standard and advanced techniques, including X-ray fluorescence (XRF), X-ray diffraction(XRD), scanning electron microscopy (SEM), and inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The XRF only shows the presence of REEs from all three fly ash samples with a range of 40 to 100 ppm and mineral oxide ranging from 0.1 to 50 %. The XRD results show that fly ash sample is a siliceous-rich sample with abundant minerals such as quartz (SiO2), magnetite (Fe3O4), and mullite (Al4.52Si1.48O9.74). The SEM analysis of the sample confirmed the presence of rare earth minerals, including monazite which is a light atomic mass (LREE), xenotime, a heavy atomic mass (HREE), and perrierite-bearing minerals. The results obtained from the instrumental analysis show that the ICP-MS instrument is the more effective analytical technique for REE analysis in this context as compared to ICP-OES. Using certified reference materials, the results obtained by two acids digestion technique, acids digestion and sodium peroxide fusion in, CGL 111, CGL 124, and AMISO276, were compared to validate whether the methods are reliable. The acid digestion approach demonstrated greater effectiveness in comparison to the sodium peroxide fusion method. The recovery percentage (%) from ICP‒MS showed an excellent percentage yield (80 – 120%) compared to the ICP‒OES instrument (50 –120%). The ICP‒MS data indicate that all fly ash samples have a high concentration of LREEs and a lower concentration of HREEs. Excellent recovery was obtained by ICP‒MS in a developed microwave acid digestion method. The concentration of REEs obtained from ICP - MS and OES in fly ash samples ranged from 50 ppm to 200 ppm for light rare earth elements and 0.5 ppm to 20 ppm for heavy rare earth elements. The total REE ( TREE) concentrations in all fly ash samples range from 400 ppm to 600 ppmen© 2024 University of the Witwatersrand, Johannesburg. All rights reserved. The copyright in this work vests in the University of the Witwatersrand, Johannesburg. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of University of the Witwatersrand, Johannesburg.REEsFly ashMulti-acid digestionFusionSDG-15: Life on landDissertationUniversity of the Witwatersrand, Johannesburg