‘Biosorption’ of rare earth elements by the biomass of novel strains of cyanobacteria is rapid, efficient and enables recycling
The Rare Earth Elements (REEs) are a group of 17 chemically similar metals, so named because they are usually present in low concentrations (0.5-67 ppm) in the Earth’s crust. Their demand has increased steadily over the past decades as they are essential to modern technologies such as light-emitting diodes, mobile phones, electric motors, wind turbines, hard disks, cameras, magnets and low-energy light bulbs. , is predicted. Further increase by 2030.
As a result of their rarity and demand, they are expensive. For example, today a kilo of neodymium oxide costs around 200 euros, while the same amount of terbium oxide costs around 3,800 euros. China currently has a near monopoly on her REE mining, but in January 2023 it was announced that a promising new ore (more than 1 million tonnes) was discovered in Kiruna, Sweden.
circular economy
The benefits of moving from a wasteful “linear” economy to a “circular” economy where all resources are recycled and reused are obvious. So can REEs be recycled more efficiently, too?
In Frontiers in Bioengineering and Biotechnology, German scientists showed that the answer is yes. The biomass of some exotic photosynthetic cyanobacteria can efficiently absorb her REEs from wastewater, for example derived from mining, metallurgy or e-waste recycling. The absorbed REEs are then washed out of the biomass and recovered for reuse.
“Here, we optimized the conditions for REE uptake by cyanobacterial biomass and characterized the most important chemical mechanisms for their binding. These cyanobacteria simultaneously recover REEs and treat industrial wastewater. ,” said Dr. Thomas Brück, professor at the Technical University of Munich and the last author of the study.
Highly specialized strains of cyanobacteria
Biosorption is a metabolically passive process for the fast and reversible binding of ions from aqueous solutions to biomass. Brück and his colleagues measured the biosorption potential of his REEs for lanthanum, cerium, neodymium, and terbium by his 12 strains of his cyanobacterium cultured in the laboratory. Most of these strains have never been evaluated for their biotechnological potential. They were sampled from highly specialized habitats, including desert dry soils in Namibia, lichen surfaces worldwide, Lake Natron in Chad, rocky crevices in South Africa and polluted streams in Switzerland. .
The authors found that the uncharacterized new species Nostoc has the highest capacity for biosorbing the ions of these four REEs from aqueous solutions, with efficiencies ranging from 84.2 to 91.5 mg/g biomass, whereas Scytonema hyalinum We found the lowest efficiency between 15.5 and 21.2 mg. g.Also efficient were Synechococcus extendes, Desmonostoc muscorum, Calothrix brevissima, and an uncharacterized new species He Komarekiella. Biosorption was found to be highly dependent on acidity. It peaked between pH 5 and 6 and steadily decreased with increasing acidity. This process was most efficient when there was no ‘competition’ for the biosorbing surface of the cyanobacterial biomass from cations of other non-REE metals such as zinc, lead, nickel, or aluminum.
The authors used a technique called infrared spectroscopy to determine which biomass functional groups were primarily responsible for REE biosorption.
“We found that cyanobacterial-derived biomass has excellent adsorption properties due to the high concentration of negatively charged sugar moieties with carbonyl and carboxyl groups. These components attract positively charged metal ions such as REEs and support their attachment to the biomass,” said first author Michael Paper, a scientist at the Technical University of Munich.
Fast and efficient, with great potential for future applications
The authors conclude that REE biosorption by cyanobacteria is possible even at low metal concentrations. This process is also fast. For example, most of the cerium in solution was biosorbed within 5 minutes of starting the reaction.
“The cyanobacteria described here are capable of adsorbing amounts of REE equivalent to up to 10% of the dry matter. It provides an economically and ecologically optimized process for the cyclical recovery and reuse of rare earth metals from industrial wastewater.”
“REE demand and market prices are likely to rise significantly over the next few years, so this system is expected to become economically viable in the near future,” he predicted.
Original: 12 Exotic Bacteria Found to Passively Collect Rare Earth Elements from Wastewater
Than: Munich Technical University
