A dozen or so bacteria are found to collect rare earth elements from wastewater

Landing elements (Rees) are a group of 17, which got their name because they usually occur by the million) in the hidden grasses of the ground. Because they are indispensable in modern technology such as light-emitting diodes, mobile phones, electromotors, turbines, hard disks, cameras, magnets and small powerful lamps, their demand has increased steadily over the past few years, and it is predicted. to increase further by 2030.

Due to their scarcity and demand, they are expensive: for example, a kilo of neodymium oxide currently costs around €200, while the same amount of terbium oxide costs around €3,800. Today, China is almost alone in the mining of REEs, although interesting new discoveries (more than one million tons) were made in Kiruna, Sweden was informed with great interest in January 2023.

Circular economy

The benefits of moving from a wasteful “standard” economy to a “circular” economy, where all resources are recycled and reused, are obvious. So can we recycle REEs efficiently, too?

Inside Advances in Bioengineering and Biotechnology, German scientists have shown that the answer is yes: The biology of some photosynthetic cyanobacteria can effectively absorb REEs from wastewater; for example those obtained from mining, metals, or recycling of electronic waste. The submerged RES can later be washed from the biomass and collected for reuse.

“Here we have improved the uptake of REE by cyanobacterial biomass, and we have described the key chemical mechanisms for binding them. These cyanobacteria can be used in future climate-friendly processes to recover REE simultaneously and and industrial water treatment,” said Dr. Thomas Brück, professor at the Technical University of Munich and author of the final study.

Specialized species of cyanobacteria

Biosorption is a fast-moving, fast-moving process that transports ions from aqueous solutions to organic matter. Brück and colleagues measured the biosorption potential of the REEs lanthanum, cerium, neodymium, and terbium by 12 species of cyanobacteria in laboratory cultures. Many of these species have never been assessed for their biotechnological potential before. They are drawn from unique habitats such as subsoil in the Namibian desert, surface lichens around the world, natron lakes in Chad, rock tunnels in South Africa, or a polluted stream in Switzerland.

The authors found that the new unspecified Nostoc species had the highest biosorption capacity of these four REE ions from aqueous solutions, with an efficiency between 84.2 and 91.5 mg per g biomass, while and Scytonema hyalinum is least effective at 15.5 to 21.2 mg per day. g. Also effective are Synechococcus elongates, Desmonostoc muscorum, Calothrix brevissima, and a new negative strain of Komarekiella. Biosorption was found to be strongly dependent on acidity: it was highest at a pH of between five and six, and decreased slowly in more acidic solutions. The process is more efficient when there is no “competition” for biosorption on the cyanobacteria biomass from positive ions of other, non-REE metals such as zinc, lead, nickel, or aluminum.

The authors used a technique called infrared spectroscopy to determine which active chemical groups in organic matter are responsible for the biosorption of REEs.

“We found that the biomass obtained from cyanobacteria has good adsorption properties due to the high content of sugars that are not good, which contain carbonyl and carboxyl groups. , “said the first author Michael Paper, a scientist at the Technical University of Munich.

Fast and efficient, with great potential for future applications

The authors concluded that biosorption of REEs by cyanobacteria is possible even at low iron concentrations. The process is also fast: for example, most of the cerium in the solution is destroyed within five minutes of starting the reaction.

“The cyanobacteria described here can adsorb amounts of REEs equal to up to 10% of their dry matter. Biosorption thus presents an economical and environmentally friendly process for the circular recovery and recycling of trace metals the world from polluted water from industries from mining, electricity, and chemical production sectors,” said Brück.

“This system is expected to be economically feasible in the near future, as the demand and market price of REEs may increase significantly in the coming years,” he said.