Finding and extracting enough rare-earth minerals to power the growing number of cell phones is a difficult challenge that can wreak havoc on the environment, but new techniques could help.
The researchers say they have removed valuable rare earth elements (REE) from the waste at yields high enough to solve manufacturers’ problems while increasing their profits. The scientists said in a recent paper that their process is more environmentally friendly because it uses less energy than other methods and turns the acid flux often used to recover elements into a trickle.
“A smartphone can contain up to eight different ETRs,” Rice University chemist James Tour, author of the study, told Digital Trends in an interview. “The red, blue and green screen colors are enhanced by the REEs, as are the vibrating mechanism and speakers.”
Minerals that keep your phone working
Tour’s lab used a special heating process that produces graphene from any solid carbon source to recover rare earth metals. Minerals have magnetic and electronic properties essential to modern electronics and green technologies.
While industrial extraction of coal fly ash, bauxite residue and e-waste typically involves strong acid — a time-consuming, non-green process — Rice Lab heats fly ash and other materials to around 5,432 degrees. Fahrenheit in a second. The process transforms the waste into highly soluble “activated rare earth species”.
Tour said the treatment of fly ash by Joule flash heating “breaks the glass that envelops these elements and converts the rare earth phosphates into metal oxides which dissolve much more easily.” Industrial processes use a concentration of 15 molar nitric acid to extract materials; the Rice process uses a much milder concentration of 0.1 molar hydrochloric acid which yields even more product.
The researchers found that instant heating of coal fly ash (CFA) more than doubled the yield of most rare earth elements using a very mild acid compared to leaching untreated CFAs in strong acids.
“The strategy is general for various wastes,” said Bing Deng, one of the researchers. “We proved that REE recovery efficiencies were improved from coal fly ash, bauxite tailings and e-waste by the same activation process.”
Deloitte Global predicts that smartphones – the world’s most popular consumer electronics device expected to have an installed base of 4.5 billion in 2022 – will generate 146 million tonnes of CO2 or equivalent emissions this year alone.
“The rapid turnover of new phones every year is a problem because we consume technology at a rapid rate, which also has environmental impacts,” said Alexander Gysi, professor in the Department of Earth and Earth Sciences. environment at the New Mexico Institute of Mining and Technology. , Digital Trends said in an interview.
While recycling would help reduce emissions, mining is still cheaper and necessary to meet the growing demand for technological devices, Gysi said. Every year their components become smaller and lighter, have longer battery life and are remixed to increase the quality of displays, he added.
“Our cell phones are supercharged with rare earths and other metals like copper and gold; it would therefore be advantageous to be able to reuse some of the parts to extract the rare earths, but we are not there yet. »
Gysi said extracting rare earths from natural mineral deposits can be difficult because these different rare earths occur together in various types of minerals. Mineral extraction requires mechanical or physical separation as well as chemical separation.
“This process can also involve chemicals that need to be carefully handled via mining waste reclamation,” Gysi said. “With mining and extraction regulations in North America, it might be beneficial to do it locally and responsibly, but it is likely to be more expensive and requires incentives to do so.”
Gysi’s laboratory is working on new REE extraction techniques. Researchers studied how REEs are chemically separated in natural systems in supercritical hydrothermal fluids in the Earth’s crust.
“They are basically water solutions at high temperature and pressure,” Gysi said. “We are studying how different acids/bases and ligands like chloride, fluoride and hydroxyl can bind to rare earths, improve their solubility and even help break them down. This will help predict the solubility and fractionation behavior of these metals and could also be used to develop new technologies.
New ways to find minerals
Computers could also boost efforts to find rare minerals. The researchers proposed an artificial intelligence (AI) system that could study a database of rare-earth minerals, recognize patterns, and then allow it to spot new potential matches.
Before the advent of AI or machine learning (ML), the discovery of new materials was based on trial and error, said materials scientist Prashant Singh, of Iowa State University’s Ames Laboratory. and author of the new study, to Digital Trends in an interview.
“The process of bringing a newly discovered material from the lab to the market can take 20-30 years, but AI/ML can dramatically speed up this process by simulating material properties on computers before setting foot in a lab,” Singh said. “This makes AI/ML useful for discovering technologically useful compounds.”