There are 118 elements on the periodic table. The familiar ones include hydrogen (1), oxygen (8), as well as the noble gases helium (2) and neon (10). But there is a subset of the periodic table that includes less familiar elements. Count among them atomic numbers 57 through 71 — a group of metallic chemicals collectively referred to as “lanthanides,” or rare earth metals.
Found in the Earth’s crust, these rare earth metals are valued for their unique magnetic, optical, and catalyst properties. Many of the items we take for granted in modern life consumer electronics, computers, clean energy, health care technology depend on lanthanides to perform with the efficiency, speed, and durability to which we’ve grown accustomed.
China currently controls approximately 97 percent of the world supply of rare earth metals and oxides, says David Hatchett, a chemistry professor at UNLV. For the rest of the world this, obviously, is a source of some consternation.
“China is reducing exports and increasing prices to foreign consumers,” says Hatchett, who has been developing a more efficient way to separate rare earth metals from mineral deposits for six years. “The global impact of these restrictions is greatest in countries with large high-tech manufacturing sectors such as the USA, Japan, and Germany.”
Lanthanides are typically found in mineral deposits that require laborious and costly processing and refinement. They are difficult to extract a characteristic that defines them as much as their silver color, sensitivity to contamination, and sometimes high levels of reactivity.
Like most processors, the Chinese typically rely on an “acid-leach” process — essentially exposing material containing rare earths to a chemical bath — to extract the desired elements. Contaminated water left over is then consigned to waste pits. Unfor tunately, these pits are seldom effective in keeping acids and other contaminants from leaking into groundwater. In China, where regulation is lax and there are few environmental protections, local residents are left to live with the environmental fallout.
Hatchett and his research team believe there is a better way. They are the principal investigators on a patent protecting their process of electrochemically recovering and separating a variety of rare earth metals. It is a process that would decrease the cost of processing high purity metals. The new separation technology, Hatchett says, enables more rapid, flexible, efficient, and environmentally friendly extraction and separations of individual lanthanides from mixtures.
“We discovered a way to electrically reclaim these rare earth metals and possibly separate them,” he says. “The refining process produces a mixture of rare earth metals, but if you can separate out the one you want and leave the other stuff behind, it is a beneficial process.
“It is an electrochemical approach rather than a chemical approach, meaning we are not using leach pits and taking the extract out to neutralize,” he adds. “We actually dissolve the materials directly into an ionic liquid, and we then electrochemically recover one in the presence of others. We use an electrode to collect the one species we want.”
In terms of materials, rare earth metals are the hardest to reduce, Hatchett explains. They are extremely electropositive, meaning they don’t want to be reduced to metal. They are not found in nature as a metal.
The electrochemistry of the ionic liquid is the key. The ionic solution is a salt — not in the more familiar crystallized form, but a liquid.
“The materials we use are nonvolatile, environmentally stable, and they provide high electrochemical reduction potentials,” he says. “The process allows us to reuse the materials because the solvent or ionic liquid doesn’t degrade.”
Hatchett says the next question is to determine if this process is cost effective.
This method isn’t just for mining rare earth metals from the Earth; it could also be used for consumer-based recycling. Rare earth metals are present in many materials that are discarded, such as fluorescent light bulbs. Hatchett notes that there might be a time when it will be financially feasible to reclaim these materials. His team’s process could conceivably be used for reclaiming rare earth materials found in discarded electronics.
The process may also be useful in recover ing rare earth metals from spent nuclear fuel or from manufacturing byproducts, as well as in the mining industry, according to Zach Miles, associate vice president of economic development.
“The prospect of introducing a less toxic, more efficient process for recovering or separating these materials would be a tremendous opportunity for a number of industries,” he says. “The research opens the possibilities for new types of industry as well.”
Miles added that the process is represented in two published patents and is available for licensing by the university.
