Lithium (Li) and Rare Earth Elements (REEs) Potential Assessment in the Coal Bottom Ash from Sonichar (Tchirozérine, Niger)

Coal Bottom Ash (CBA) is an important second source of strategic metals such as Lithium (Li) and Rare Earth Elements (REEs). Its recovery generates new strategic resources in the current climate and environmental context. It is in this context of resource circularity that this study aims to assess the economic potential of Li and REEs in six CBA samples from Sonichar, in Niger. X-ray diffraction and chemical (XRF and ICP-MS) analyses were performed on the six CBA samples to determine their mineralogical and chemical composition (oxides, Li and REEs). The Enrichment Coefficient (EC), the percentages of critical metals (Cp), excessive metals (Ep) and non-critical metals (Up), as well as the economic prospectivity coefficient (Cout1), were used to assess the economic potential for Li and REEs recovery. The main oxides present in the CBA are: SiO2 (51.99%), Al2O3 (23.79%) and Fe2O3 (4.43%). The main minerals are: mullite (70.16%), quartz (29.21%) and hematite (0.63%). The CBA samples have high Li contents, ranging from 89.65 to 109.59 mg/kg, and low REE contents, all of which decrease from MC1 (< 80 μm) to MC6 (16-20 mm). The EC values for Li range from 5.48 to 4.48 (EC > 1). These EC values indicate Li enrichment. All the REEs EC values were below 1 (EC < 1). The Li and REEs EC values increase as the particle size decreases. The parameters used to assess the economic potential of REEs gave the following results: CpMean = 33.03%, EpMean = 39.03%, UpMean = 27.94%, and CoutlMean = 0.85. Taking into account the average values of CpMeam = 33.03% and Cout1Mean = 0.85, the Sonichar CBA can be considered a promising secondary source for the recovery of REEs. This study opens up prospects for the extraction of Li and REEs contained in the Sonichar CBA. Major Findings: This study confirms the Li and REEs potential of the Sonichar Niger CBA, with an enrichment coefficient > 5 for Li, and a critical metals percentage of 33.03% and an economic prospectivity coefficient of 0.85 for REEs, making the Sonichar CBA a promising secondary source for the recovery of Li and REES.