Untargeted metabolomics reveals the mechanism for leaching rare earth elements from ion-adsorption rare earth ores using a composite lixiviant

Rare earth elements (REEs) are an important strategic scarce resource, and how to mine and utilise them efficiently and greenly is a difficult problem. In this study, to reduce the use of chemical reagents in the leaching process, Bacillus thuringiensis fermentation broth and magnesium acetate were used as composite lixiviants to leach REEs from ionic rare earth ores via biochemical synergy. The effectiveness of composite lixiviant for leaching REEs was studied, and the optimum leaching conditions were determined. In addition, untargeted metabolomics was used to explore metabolite differences and metabolic pathway profiles before and after leaching with the composite lixiviant. The interaction between the composite lixiviant and the rare earth minerals was also investigated by combining various characterisation tools. The results showed that the leaching rate was 96.3 % when the concentration of magnesium acetate in the composite lixiviant was 0.3 mol/L, the pH was 4, and the liquid-solid ratio was 2:1. Metabolomics analysis showed that lipids and lipid-like molecules, benzenoids, and organic acids, and derivatives contained in the fermentation broth of the complex leach play an important role in the leaching process. This study provides a new composite lixiviant for leaching ionic REEs, which can reduce the dosage of chemical reagents, provide a reference for the biochemical synergistic leaching of ionic rare earth ores, and help guide environmentally friendly and efficient leaching of ionic rare earth ores in the future.