Common Solutions for Rare Earths?

November 29, 2022

Don’t assume that future extraction of vital minerals and “rare” earths will utilize the same processes that have been used historically. Huge incentives now to work on this challenge. Just a few ideas here.

Rice University:

The Rice lab of chemist James Tour reports it has successfully extracted valuable rare earth elements (REE) from waste at yields high enough to resolve issues for manufacturers while boosting their profits. 

The lab’s flash Joule heating process, introduced several years ago to produce graphene from any solid carbon source, has now been applied to three sources of rare earth elements — coal fly ashbauxite residue and electronic waste — to recover rare earth metals, which have magnetic and electronic properties critical to modern electronics and green technologies.

The researchers say their process is kinder to the environment by using far less energy and turning the stream of acid often used to recover the elements into a trickle.

The study appears in Science Advances.                                                             

Rare earth elements aren’t actually rare. One of them, cerium, is more abundant than copper, and all are more abundant than gold. But these 15 lanthanide elements, along with yttrium and scandium, are widely distributed and difficult to extract from mined materials.

“The U.S. used to mine rare earth elements, but you get a lot of radioactive elements as well,” Tour said. “You’re not allowed to reinject the water, and it has to be disposed of, which is expensive and problematic. On the day the U.S. did away with all rare earth mining, the foreign sources raised their price tenfold.”

So there’s plenty of incentive to recycle what’s been mined already, he said. Much of that is piled up or buried in fly ash, the byproduct of coal-fired power plants. “We have mountains of it,” he said. “The residue of burning coal is silicon, aluminum, iron and calcium oxides that form glass around the trace elements, making them very hard to extract.” Bauxite residue, sometimes called red mud, is the toxic byproduct of aluminum production, while electronic waste is from outdated devices like computers and smart phones.   

While industrial extraction from these wastes commonly involves leaching with strong acid, a time-consuming, non-green process, the Rice lab heats fly ash and other materials (combined with carbon black to enhance conductivity) to about 3,000 degrees Celsius (5,432 degrees Fahrenheit) in a second. The process turns the waste into highly soluble “activated REE species.”

Tour said treating fly ash by flash Joule heating “breaks the glass that encases these elements and converts REE phosphates to metal oxides that dissolve much more easily.” Industrial processes use a 15-molar concentration of nitric acid to extract the materials; the Rice process uses a much milder 0.1-molar concentration of hydrochloric acid that still yields more product.

In experiments led by postdoctoral researcher and lead author Bing Deng, the researchers found flash Joule heating coal fly ash (CFA) more than doubled the yield of most of the rare earth elements using very mild acid compared to leaching untreated CFA in strong acids.

“The strategy is general for various wastes,” Bing said. “We proved that the REE recovery yields were improved from coal fly ash, bauxite residue and electronic wastes by the same activation process.” 

The generality of the process makes it especially promising, Bing said, as millions of tons of bauxite residue and electronic waste are also produced every year.

“The Department of Energy has determined this is a critical need that has to be resolved,” Tour said. “Our process tells the country that we’re no longer dependent on environmentally detrimental mining or foreign sources for rare earth elements.”

Tour’s lab introduced flash Joule heating in 2020 to convert coal, petroleum coke and trash into graphene, the single-atom-thick form of carbon, a process now being commercialized. The lab has since adapted the process to convert plastic waste into graphene and to extract precious metals from electronic waste.

FIGURE 5. SEM micrograph of natural walnut shell before and after rare-earth elements adsorption at 700×. (A) Natural walnut shell (WS); (B) Nd adsorption onto WS; (C) La adsorption onto WS; (D) Gd adsorption onto WS; (E) Sm adsorption onto WS; (F)Eu adsorption onto WS. Arrows indicate the presence of porous.

Frontiers:

Agricultural wastes are considered as green adsorbents that can work as an alternative to recover critical and scarce metals from secondary sources. Critical elements as rare-earth elements (REEs) can be obtained from electronic wastes or tailings and could be recovered using these green alternatives. In this study, walnut shell (WS) was tested to determine whether several REEs can be efficiently retained by this green adsorbent.

Employment of walnut shell as a raw material for the adsorption of metals is a useful recycling process. The good adsorption capacity and removal efficiency of WS might be successfully used for adsorbing Eu, La, Sm, and Gd from aqueous solution.

It is concluded that WS is a green and environmentally friendly biomaterial with high capacity toward retaining several metals, specifically REEs. Moreover, although no activation was done, we could obtain high adsorption with natural WS, becoming in excellent results for upcoming work. Then, WS has the potential to be used in the future to recover REEs from different secondary sources, such as waste electrical and electronic equipment (WEEE) or mine tailing, and to contribute to circular economy.

SciTechDaily:

Copper remains one of the single most ubiquitous metals in everyday life. As a conductor of heat and electricity, it is utilized in wires, roofing, and plumbing, as well as a catalyst for petrochemical plants, solar and electrical conductors, and for a wide range of energy-related applications. Subsequently, any method to harvest more of the valuable commodity proves a useful endeavor.

Debora Rodrigues, Ezekiel Cullen Professor of Engineering at the University of Houston Cullen College of Engineering, in collaboration with Francisco C. Robles Hernandez, professor at the UH College of Technology and Ellen Aquino Perpetuo, professor at the University of Sao Paulo, Brazil offered conclusive research for understanding how bacteria found in copper mines convert toxic copper ions to stable single-atom copper.

In their co-authored paper, “Copper Mining Bacteria: Converting toxic copper ions into a stable single atom copper,” their research demonstrates how copper-resistant bacterium from a copper mine in Brazil convert CuSO(copper sulfate) ions into zero-valent Cu (metallic copper).

“The idea of having bacteria in mines is not new, but the unanswered question was: what are they doing in the mines?” Robles said. “By putting the bacteria inside an electronic microscope, we were able to figure out the physics and analyze it. We found out the bacteria were isolating single atom copper. In terms of chemistry, this is extremely difficult to derive. Typically, harsh chemicals are used in order to produce single atoms of any element. This bacterium is creating it naturally that is very impressive.”

In their co-authored paper, “Copper Mining Bacteria: Converting toxic copper ions into a stable single atom copper,” their research demonstrates how copper-resistant bacterium from a copper mine in Brazil convert CuSO(copper sulfate) ions into zero-valent Cu (metallic copper).

“The idea of having bacteria in mines is not new, but the unanswered question was: what are they doing in the mines?” Robles said. “By putting the bacteria inside an electronic microscope, we were able to figure out the physics and analyze it. We found out the bacteria were isolating single atom copper. In terms of chemistry, this is extremely difficult to derive. Typically, harsh chemicals are used in order to produce single atoms of any element. This bacterium is creating it naturally that is very impressive.”

“The novelty of this discovery is that microbes in the environment can easily transform copper sulfate into zero valent single atom copper. This is a breakthrough because the current synthetic process of single atom zerovalent copper is typically not clean, it is labor intensive and expensive,” Rodrigues said.

“The microbes utilize a unique biological pathway with an array of proteins that can extract copper (II) (Cu2+) and convert it into single-atom zero-valent copper (Cu0). The aim of the microbes is to create a less toxic environment for themselves by converting the ionic copper into single-atom copper, but at the same time they make something that is beneficial for us too.”

Wiki:

Biomining is the technique of extracting metals from ores and other solid materials typically using prokaryotes, fungi or plants (phytoextraction also known as phytomining or biomining).[1] These organisms secrete different organic compounds that chelate metals from the environment and bring it back to the cell where they are typically used to coordinate electrons. It was discovered in the mid 1900s that microorganisms use metals in the cell. Some microbes can use stable metals such as ironcopperzinc, and gold as well as unstable atoms such as uranium and thorium. Large chemostats of microbes can be grown to leach metals from their media. These vats of culture can then be transformed into many marketable metal compounds. Biomining is an environmentally friendly technique compared to typical mining. Mining releases many pollutants while the only chemicals released from biomining is any metabolites or gasses that the bacteria secrete. The same concept can be used for bioremediation models. Bacteria can be inoculated into environments contaminated with metals, oils, or other toxic compounds. The bacteria can clean the environment by absorbing these toxic compounds to create energy in the cell. Bacteria can mine for metals, clean oil spills, purify gold, and use radioactive elements for energy.

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7 Responses to “Common Solutions for Rare Earths?”

  1. jimbills Says:

    To get a sense of the scale of the problem, there’s this:

    EVs Only Displaced 2 Days Worth of Gas Consumption Over the Last Decade
    https://www.yahoo.com/lifestyle/evs-only-displaced-2-days-213000155.html

    ‘Electric vehicles may seem like the future, but it’s a future that is still a far way off, according to a new report from the U.S. Department of Energy’s Argonne National Lab covering the affect of EVs over the last decade.

    The lab comes at you with some interesting and ultimately depressing numbers. While EVs have grown in popularity since 2010, they still only represent four percent of the market at the end of 2021.’

    ‘Right now, EVs make up one percent of all vehicles on the road, but have only reduced gasoline consumption half a percent thanks to dropping PHEV electrical range and the resurrection of the gas-guzzler.’

  2. redskylite Says:

    We need to curb our enthusiasm for our personal car. . . . .. …

    “Conversations about reducing these emissions typically focus on electric vehicles. But increasingly, government officials across the country are aiming not just to get Americans into different kinds of cars, but to radically reduce the need to drive in the first place.”

    https://yaleclimateconnections.org/2022/11/state-local-governments-increasingly-turn-to-zoning-reforms/

  3. John Oneill Says:

    The radioactive elenent in rare earth deposits is usually thorium (and a few of its daughter isotopes). It’s very weakly radioactive – the half-life is about the same as the age of the universe, about 14 billion years. Thorium should be quite a useful metal – it used to make the mesh shroud around gas lamps because of its extremely high melting temperature. As a fertile nuclear fuel, it’s been used in a few power plants – Fort st Vrain, in Colorado, and Indian Point 1, in New York. As it’s mot being used now, it’s effectively worthless, but known reserves have enough energy to run the whole world economy for thousands of years.


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