Successfully extracted rare earth element from waste

Rice University has successfully recovered rare earth elements from trash with important properties for electronics and green technology.

There is an interesting fact: rare earth elements (REEs) are not in fact rare. However, all REEs are often not centrally distributed and are difficult to extract from mined minerals.

This is really a problem because REE is a necessary component of more than 200 products across many applications, especially high-tech consumer products such as mobile phones, computer hard drives, electric vehicles, hybrid car, flat screen and TV.

A few years ago, scientists from Rice University in the US devised a beam-resistant heating (FJH) technique to create graphene from any solid carbon-based waste, and in a new study. , they went on to successfully apply this method to three waste sources - fly ash, bauxite residue and e-waste - to recover rare earth metals.

Microscopic glass spheres found in fly ash contain REE.

The United States used to mine rare earth elements, but also obtained a lot of radioactive elements. They are not allowed to re-supply the water to treat them as this is very costly and has environmental consequences, resulting in a complete stoppage of the mining operation. Today, much of what is mined is piled up or buried in fly ash, a by-product of coal-fired power plants.

"We have mountains of fly ash. The residue of burning coal is oxides of silicon, aluminum, iron and calcium that form glass around the trace elements, making them very difficult to extract," said chemist James Tour, co-author of the study. author of the study, said. "Bauxite residue, sometimes called red mud, is a toxic byproduct of aluminum production, while e-waste originates from obsolete devices such as computers and smartphones."

The industrial extraction of these waste sources often entails strong acid leaching, which is both time consuming and harmful to the environment. In the new Rice University method, the researchers heated fly ash and other materials combined with carbon black to increase conductivity to about 3,000 degrees Celsius for one second. That allows them to convert waste into highly reactive REEs, with magnetic and electronic properties important for electronics and green technology.

Tour says the FJH fly ash technique breaks down the glass that encapsulates the elements and converts REE phosphates into much more soluble metal oxides. The generality of the process is what makes it so promising as millions of tons of bauxite and e-waste are generated each year.