Rare Earth elements (RREs) are vital for building technological equipment, including computers, cell phones, microphones, wind turbines, electric vehicles, radars, sonars, LED lights, rechargeable batteries, and conductors. However, refining them after mining is quite costly, and has a negative impact on the environment.
A new study led by Cornell University describes the principle for engineering a bacterium (Gluconobacter oxidans) which can offer a sustainable alternative to environmentally harmful thermochemical extraction and refinement methods.
“We’re trying to come up with an environmentally friendly, low-temperature, low-pressure method for getting rare earth elements out of a rock,” said study senior author Buz Barstow, an assistant professor of Biological and Environmental Engineering at Cornell University.
In order to meet United States’ annual needs for REEs, 78.8 million tons of raw ore are required to extract 22,000 pounds of elements. While the United States used to refine its own rare elements half a century ago, in the past decades the refinement of REEs takes place abroad, particularly in China.
“The majority of rare Earth element production and extraction is in the hands of foreign nations,” explained study co-author Esteban Gazel, an associate professor of Earth and Atmospheric Sciences at Cornell University. “So for the security of our country and way of life, we need to get back on track to controlling that resource.”
While previous methods of extraction relied on dissolving rocks with the help of hot sulphuric acid and using organic solvents to separate individual elements, Professor Barstow and his team discovered that the bacterium G. oxydans can be used to perform this process much more efficiently.
G. oxydans employs an acid called biolixiviant that can dissolve rock and pull phosphates from REEs. The scientists started manipulating the bacterium’s genes so that it extracts the elements in a more efficient manner.
For this, they used a technology called Knockout Sudoku, which allowed them to disable the 2,733 genes in G. oxydans’ genome one by one. The researchers curated mutant bacteria, each with a specific gene knocked out, in order to identify which genes play roles in extracting elements out of rock, and thus devise a more efficient and sustainable extraction method.
“I am incredibly optimistic. We have a process here that is going to be more efficient than anything that was done before,” Professor Gazel concluded.
The study is published in the journal Nature Communications.