Green Strategy for Bioleaching of Poorly Soluble Neodymium Compounds by Microscopic Fungi

Currently, environmentally friendly processes for processing raw materials containing rare earth elements (REEs) are being actively developed. Microorganisms play an important role in the biogeochemistry of REEs, but the nature of the interaction of micromycetes with REEs remains poorly understood. This study examines the potential of extracting REEs from their insoluble forms using microscopic fungi. Using the example of the soil micromycete Aspergillus niger, the possibility of converting poorly soluble neodymium oxide Nd2O3 into water- and alcohol-soluble (ethyl and isopropyl) neodymium compounds is shown. The morphology and structure of A. niger cells and the distribution of insoluble and soluble forms of this rare earth element before and after bioleaching were studied using scanning electron microscopy (SEM). Bioleaching by micromycetes was modeled using the direct contact method. X-ray fluorescence analysis of extracts after bioleaching showed the presence of neodymium. These studies will help unlock the potential of microscopic fungi for their application in an environmentally friendly technology for the extraction of REEs based on bioleaching. This may serve as a basis for the development of an environmentally friendly alternative to the methods employed currently, which use strong inorganic acids or toxic substances.