Scientists have learned to extract rare earth metals from algae

American researchers have discovered a new way of mining precious rare earth metals.

It is noted, that the scientists focused on algae containing elements of rare earth metals in leaf-like tissues. As a result of numerous efforts, a research team from The US Pacific Northwest National Laboratory was able to extract critical minerals from seaweed biomass. 

In particular, scientists grow several types of seaweed on the Sekim campus and are exploring various methods of extracting minerals from them. Rare earth elements, in particular, neodymium, remain one of the key elements in electronic devices, vehicles, and buildings. They are traditionally extracted from rocks. 

According to a plant researcher from the laboratory Sekim Scott Edmundson, seaweed is a great collector of minerals. And although researchers still don’t know, the exact reasons, why this is so, they found, that algae scattered along the shoreline could contain various important minerals. In some cases, the concentration of these minerals in the algae was more than a million times higher than similar indicator in seawater. 

The researchers studied different types of algae to determine what minerals they might contain and in what quantities. They found, that a species of leathery brown algae called fucus is particularly good at concentrating nickel in its tissues.

At the same time, the green leafy algae ulva, better known as sea lettuce, is the best at concentrating several types of valuable minerals at once. After testing several methods, the research team settled on a process that initially showed very good results. After growing a sufficient amount of algae, the scientists crushed it to a homogeneous mass and then mixed it with an acidic liquid that could break down the mineral in question.

Acidic liquids, known as “leachers”, are used in standard ore mining to extract minerals from rocks. When the seaweed paste is mixed with the leaching agent, the pH of the mixture decreases (or becomes more acidic), which leads to the separation of the target mineral from the algae. The mixture is also exposed to high temperatures, which can contribute to the destruction of chemical bonds.

As noted by Michael Husemann, the primary objective of the research team is to extract at least 50% of the critical minerals from the seaweed biomass. However, it turned out to be a very difficult task. The researchers experimented with different leaching agents and temperatures, and processed the mixture several times to extract as many critical minerals as possible.

Researchers have found that improving the — mining method is only the beginning. To make this extraction profitable, scientists are conducting a cost-benefit analysis. Previously, scientists dried algae by heating. However, they later abandoned this method to save energy.

Leaching agents are another source of costs, so researchers are exploring the possibility of using waste acids generated in other processes, such as increasing the alkalinity of the ocean to produce minerals. A group of scientists has discovered that seaweed grows quickly and does not require fresh water, and after extracting minerals, the remaining biomass can be reused, for example, as a raw material for biofuels or for the production of bioproducts such as plastics, building materials, or even adhesives.

Source: Interesting Engineering