Thomas Bruck
Demand for rare earth elements is growing and could reach 315,000 tons by 2030. Meanwhile, more than 40 million tons of e-waste (discarded computers, mobile phones and other electronic devices) are generated each year. Some of that waste contains the same valuable elements that face increased demand.
Over the years, several notable methods have been proposed for the recovery of spent or waste-based rare earth elements. For example, urban mining and nanofiltration systems in rivers. One persistent idea is to use micro-organisms such as bacteria to “bio-absorb” the desired substance. It is a passive biological process in which organisms combine to remove substances from aqueous solutions. The technology has yet to be deployed at an industrial level, but some researchers suggest the latest findings represent a major step forward.
In a recent paper, Professor Thomas Brück and his colleagues at the Technical University of Munich, who study synthetic biotechnology and sustainability, say they have identified 12 exotic cyanobacterial species that are particularly good at absorbing rare earth elements. I’m here. These seeds can be used to regenerate desirable elements while purifying land and water. “[I]This is not what we predicted,” Brück told Ars.
unusual suspect
This study was conducted over a period of 6 years. The team began screening various algae and bacteria, but none were particularly good at absorbing rare earth elements. So they turned their attention to a dozen species of cyanobacteria. Some came from environments that were particularly inhospitable to most life forms. For example, Lake Natron is unusually alkaline, with a pH of around 10 and temperatures that can reach 60º C (or 140º F). Brück says it’s unclear whether how these organisms evolved to thrive in these environments contributed to their ability to devour rare earth elements.
In many cases, the species came from very specific habitats, such as the arid desert soils of Namibia, the alkaline Lake Natron of Chad, the rock crevices of South Africa, and the polluted streams of Switzerland. These were “really unique and extreme environments,” Brück said.
Most of these bacteria have not previously been evaluated for their bioremediation potential. In the lab, the team exposed cultures of different species to aqueous solutions containing the rare earth elements lanthanum, cerium, and neodymium, and used infrared spectroscopy to see how well those elements were retained on the surface. .
One of the previously uncharacterized species Nostock Cyanobacteria performed best. Bioabsorption of the four rare earth elements from solution resulted in 84.2–91.5 mg of metal uptake per gram of biomass.it was the worst performance Scytonema hyalinum 15.5-21.2 mg per gram of biomass. However, the paper noted that how well each candidate performs depends on its acidity, and the process is more efficient when there are no other metals in solution that compete with the target rare earth element.
Dirty, uh, clean dozen
It is also possible and relatively easy to extract the desired rare earth elements from biomass. It simply changes the pH of the solution using something like acid or lye, or changes the salinity. Elements are only functionally “washed out” of the biomass. Restoring the solution allows the process to start over. This means that cyanobacterial cultures may be reused.
“It’s not a one-time deal where you have to burn the biomass to recover the metals at the end of the bond,” Brück said.
Researchers and industry players can create bioreactors (specialized vessels containing microbial biomass) for some future applications. One can be used to collect rare earth elements from e-waste waste, but this requires converting the e-waste into a form that can be used by microorganisms. It provides environmental benefits as it can be removed and jobs can be created in parts of the world where e-waste is regularly shipped from the Global North such as Nigeria, Ghana and Tanzania. Brück then added that it can be used to clean up and recover these elements from industrial effluents such as the mining and chemical industries.
According to Brück, the research could be a big step forward. From this point on, researchers hope to scale up significantly. This is something that has not yet happened in this area. We plan to work with partners from various industries to make this happen, but it is a difficult prospect given that it is a highly specialized process. It is different from growing corn in agriculture and traditional metal refining methods. Still, researchers are hopeful about the results.
“I think we’re at a point now where we can say, ‘Hey, we can make this work,'” said Brück.
Frontiers, 2023. DOI: 10.3389/fbioe.2023.1130939 (About DOI)
