Publication: The characterization study of rare earth elements in Mukah coal fly ash
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Date
2024-08-01
Authors
Leslie Sie Kai Sheng
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Abstract
Coal fly ash (CFA) is a potential secondary Rare Earth Element (REE) source that needs an efficient enrichment and extraction process. In this project, the beneficiation studies are carried out on the coal fly ash samples collected from Mukah-Balingian, Sarawak. This study aimed to characterize the CFA and identify the possible minerals that REEs are bound to in CFA by physical separation and sequential leaching. The raw CFA, containing 68.474 ppm of REE and over 24% of key rare earth elements (total REY), is characterized by a high outlook coefficient (Coutlook) ranging from 1.0 to 1.2, indicating potential for enrichment. Major elements identified include silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃), comprising approximately 50% and 30% of the sample, respectively, along with minerals such as quartz, magnetite, lime, and silica polymorphs. The XRD results reveals a complex mineralogical structure and the prevalence of finer particles, minerals such as quartz, magnetite, lime, and silica polymorphs, underscoring the need for tailored enrichment methods. Wet magnetic separation results showed a significant difference of 7% in MgO content between the non-magnetic and magnetic fractions, with REEs detected in both. If REEs are associated with MgO, magnetic separation can serve as an enrichment method. However, sequential leaching results indicate that only 1.46% of REEs are found in the amorphous manganese oxide, making this fraction negligible. Sequential leaching identified the binding of REEs mainly within the aluminosilicate glassy phase, with weak acids unable to extract significant amounts. Consequently, pretreatment processes like alkali fusion or alkali leaching are recommended for effective REE extraction from CFA.