Bioleaching of Phosphate Minerals Using Aspergillus niger: Recovery of Copper and Rare Earth Elements

Abstract

Rare earth elements (REE) are essential in high-technology and environmental applications, where their importance and demand have grown enormously over the past decades. Many lanthanide and actinide minerals in nature are phosphates. Minerals like monazite occur in small concentrations in common rocks that resist weathering. Turquoise is a hydrous phosphate of copper and aluminum scarcely studied as copper ore. Phosphate-solubilizing microorganisms are able to transform insoluble phosphate into a more soluble form which directly and/or indirectly contributes to their metabolism. In this study, bioleaching of heavy metals from phosphate minerals by using the fungus Aspergillus niger was investigated. Bioleaching experiments were examined in batch cultures with different mineral phosphates: aluminum phosphate (commercial), turquoise, and monazite (natural minerals). The experiments were performed at 1% pulp density and the phosphorous leaching yield was aluminum phosphate > turquoise > monazite. Bioleaching experiments with turquoise showed that A. niger was able to reach 8.81 mg/l of copper in the aqueous phase. Furthermore, the fungus dissolved the aluminum cerium phosphate hydroxide in monazite, reaching up to 1.37 mg/L of REE when the fungus was grown with the mineral as the sole phosphorous source. Furthermore, A. niger is involved in the formation of secondary minerals, such as copper and REE oxalates.

The Role of Microorganisms in Mobilization and Phytoextraction of Rare Earth Elements: A Review

“…Other studies reported that the highest percentages of bioleached total RE from monazite and (Th-U) concentrate directly by Aspergillus ficuum, are found to be 75.4 and 63.8% at a pulp density 0.6 and 1.2% (w/v), respectively, after 9 days and 63.5 and 52.6% by Pseudomonas eruginosa after 8 days (Hassanien et al, 2014). Also, fungal strains able to solubilize phosphate minerals such as A. niger have shown potential for RE bioleaching from monazite (Castro et al, 2020). Several other fungal strains have been also used to leach monazite releasing RE to the aqueous phase such us Aspergillus terreus, Paecilomyces spp.…”

“…and Penicillum sp. that can release a total concentration of 12.32 mg/L RE (Ce, La, Nd, and Pr) from the weathered monazite after 8 days (Castro et al, 2020). Another study with A. niger reported that the highest rates of RE from monazite were obtained when the fungus was cultivated on minimal medium with the mineral as the sole phosphorous source.…”

Biohydrometallurgy for Rare Earth Elements Recovery from Industrial Wastes

“…Most of the REE bioleaching studies that have been developed have treated mineral ores with a variety of microorganisms. Phosphate-solubilizing microorganisms are particularly relevant in the bioleaching of monazite because they transform insoluble phosphate into more soluble phosphorous forms [3,23,24]. The mineral phosphate solubilization occurs through the biological generation of organic acids and the proton substitution reaction:…”

Leaching/Bioleaching and Recovery of Metals

“…The transition from fossil fuels to renewable energy and the development of new technologies have increased the mining of strategic metals and nonconventional minerals. Castro et al [5] investigated the dissolution of heavy metals from phosphate minerals (aluminum phosphate, turquoise, and monazite) using the fungus Aspergillus niger. A. niger was able to reach 8.81 mg/L of copper and up to 1.37 mg/L of REE in the aqueous phase.…”