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Rare earth elements could be pulled from coal waste

In Appalachia’s coal country, researchers envision turning toxic waste into treasure. The pollution left behind by abandoned mines is an untapped source of rare earth elements.

Rare earths are a valuable set of 17 elements needed to make everything from smartphones and electric vehicles to fluorescent bulbs and lasers. With global demand skyrocketing and China having a near-monopoly on rare earth production — the United States has only one active mine — there’s a lot of interest in finding alternative sources, such as ramping up recycling.

Pulling rare earths from coal waste offers a two-for-one deal: By retrieving the metals, you also help clean up the pollution.

Long after a coal mine closes, it can leave a dirty legacy. When some of the rock left over from mining is exposed to air and water, sulfuric acid forms and pulls heavy metals from the rock. This acidic soup can pollute waterways and harm wildlife.

Recovering rare earths from what’s called acid mine drainage won’t single-handedly satisfy rising demand for the metals, acknowledges Paul Ziemkiewicz, director of the West Virginia Water Research Institute in Morgantown. But he points to several benefits.

Unlike ore dug from typical rare earth mines, the drainage is rich with the most-needed rare earth elements. Plus, extraction from acid mine drainage also doesn’t generate the radioactive waste that’s typically a by-product of rare earth mines, which often contain uranium and thorium alongside the rare earths. And from a practical standpoint, existing facilities to treat acid mine drainage could be used to collect the rare earths for processing. “Theoretically, you could start producing tomorrow,” Ziemkiewicz says.

From a few hundred sites already treating acid mine drainage, nearly 600 metric tons of rare earth elements and cobalt — another in-demand metal — could be produced annually, Ziemkiewicz and colleagues estimate.

Currently, a pilot project in West Virginia is taking material recovered from an acid mine drainage treatment site and extracting and concentrating the rare earths.

If such a scheme proves feasible, Ziemkiewicz envisions a future in which cleanup sites send their rare earth hauls to a central facility to be processed, and the elements separated. Economic analyses suggest this wouldn’t be a get-rich scheme. But, he says, it could be enough to cover the costs of treating the acid mine drainage.

Source link With the world’s diminishing supply of rare earth elements (REEs) becoming an ever-increasing concern for many industries, new research has sought to explore innovative methods for obtaining them, with coal waste being identified as a potential source.

REEs are a set of 17 chemical elements that are essential for a number of technological advancements, from clean energy deployment to the production of mobile phones and electric cars. But given their scarcity, the cost of acquiring them is high and rising, prompting researchers to find ways to source them more efficiently.

A new study has suggested that coal waste could be tapped as an alternative source. The analysis – conducted by researchers at Newcastle University, UK – details how REEs can be pulled from lignite, a type of low-grade coal often mined in Europe.

Using lignite dust samples collected from power plants in the Czech Republic, the researchers developed an extraction method that allowed them to extract REEs from the coal waste. By taking advantage of the affinity of certain REEs for certain metals, the team were able to use aqua regia to separate the REEs from the coal particles.

After testing and refining the method, the researchers were able to achieve their goal of separating the rare earth elements from the coal waste. They found that up to 1% of the total REE stream came from the coal waste, a promising finding that suggests a viable pathway for recovery of these elements in the future.

The researchers have also highlighted the potential financial benefit of their findings. Not only could the technique reduce the cost of obtaining REEs for industry, but it could also generate economic value – through the sale of recovered REEs – for lignite-mining regions in Europe.

This innovative research has the potential to revolutionize the way the world sources REEs, helping to ensure more reliable and cost-effective access to these essential elements.

For more detailed report on this research, please refer to the article titled “Extraction of REEs from coal waste using aqua regia” in the International Journal of Mining, Reclamation and Environment.

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