Currently, less than 10% of neodymium is recycled [1].
Recycling neodymium from electronic waste in an environmentally sustainable and cost-effective manner poses a significant challenge. Hydrometallurgical methods, which rely on strong acids to extract neodymium from e-waste, produce substantial volumes of hazardous chemical waste. Additionally, these methods are unable to effectively separate lanthanides from other metals present in electronic waste. Pyrometallurgical approaches, while capable of separating metals, are costly and energy-intensive due to the high temperatures required for metal extraction [2].
Lanmodulin is a protein with remarkable picomolar affinity for lanthanides, making it an excellent candidate for accumulating lanthanides. By leveraging lanmodulin, we aim to reduce or even bypass the need for traditional pyrometallurgical methods, which are energy-intensive and involve harsh conditions, in the separation of lanthanides from other metals [3].
We have selected Methylobacterium extorquens because this bacterium is already equipped with the mechanisms for sensing and taking up lanthanides. By enhancing the expression of lanmodulin within M. extorquens, we can increase its capacity to store lanthanides and its propensity to uptake them [4].
Current methods for lanthanide separation, particularly pyrometallurgical processes, are well-established, efficient, and have been extensively tested. In contrast, our approach is still in the preliminary stages of development. However, a key advantage of our method lies in its ability to selectively accumulate different metals in distinct locations within the same solution, offering the potential for more efficient recycling of multiple metals simultaneously.
In the context of our project, pyrometallurgical methods would still be employed on smaller scales after lanthanides are accumulated by lanmodulin. However, our long-term goal is to refine the process such that affinity-based purification techniques could be used to isolate different lanthanides, thereby eliminating the need for energy-intensive pyrometallurgical separation in the future [5].
^[1] Royal Society of Chemistry [2016] Neodymium - element information, properties and uses: Periodic Table, Neodymium - Element information, properties and uses | Periodic Table. Available at: https://www.rsc.org/periodic-table/element/60/neodymium (Accessed: 19 September 2024).
^[2] Lockwood, D. (2023) Recycling rare earths from e-waste more sustainably, Chemical & Engineering News. Available at: https://cen.acs.org/articles/93/web/2015/07/Recycling-Rare-Earths-E-Waste.html (Accessed: 19 September 2024).
^[3] Cotruvo JA Jr, Featherston ER, Mattocks JA, Ho JV, Laremore TN. (2018) Lanmodulin: A Highly Selective Lanthanide-Binding Protein from a Lanthanide-Utilizing Bacterium. J Am Chem Soc. 140(44):15056-15061.
^[4] Vu HN, Subuyuj GA, Vijayakumar S, Good NM, Martinez-Gomez NC, Skovran E. (2016) Lanthanide-Dependent Regulation of Methanol Oxidation Systems in Methylobacterium extorquens AM1 and Their Contribution to Methanol Growth. J Bacteriol. 198(8):1250-9.
^[5] Mattocks JA, Jung JJ, Lin CY, Dong Z, Yennawar NH, Featherston ER, Kang-Yun CS, Hamilton TA, Park DM, Boal AK, Cotruvo JA Jr. (2023) Enhanced rare-earth separation with a metal-sensitive lanmodulin dimer. Nature. 618(7963):87-93.