Breakthrough in electrokinetic mining: 5,000 tons of ion-adsorption rare-earth ore successfully mined

Rare-earth elements (REEs) have been listed as “critical metals” by many countries, including China, the USA, the European Union, and Japan. Heavy REEs (HREEs) are particularly significant due to their irreplaceable use in high-tech and security applications, making them strategically important and economically valuable. Ion-adsorption deposits (IADs) of REEs are the dominant minable resources of HREEs, supplying more than 90% of the global HREEs. However, the existing IAD mining techniques, predominately ammonium-salt in situ leaching, have faced significant challenges, including severe environmental damage, low REE recovery efficiency, and extended leaching durations, leading to its governmental ban in 2018. Writing in Nature Sustainability and The Innovation, Wang et al. propose a distinctly more efficient technology, i.e., electrokinetic mining (EKM), that could help to reduce the impacts of REE mining substantially.

The working principle for the EKM technology is to utilize electromigration and electroosmosis effects generated by electricity to accelerate and direct the flow of REE fluids from the anode to the cathode. The viability of this EKM technology for REE extraction has been verified by Wang et al. at three different spatial scales, from bench-scale experiments to a small pilot test at a field site near Guangzhou. While the feasibility of the EKM technology has been demonstrated and preliminary experimental results achieved, several challenges remain during its transition to industrial-scale implementation, for example, the long-term stability of electrodes in wet, corrosive soil environments and the potential leakage of REE leachates in the actual mining process due to the complexity of the real mining ore structure and underground hydrological conditions. “The challenge from here on is to confirm the viability of the approach at industrial scale and to thoroughly verify the claimed reduction in environmental impacts,” says Henning Prommer, an environmental engineer at the University of Western Australia, Perth, whose group has worked on applying EKM to copper and gold.

The team from the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, has further improved and made significant advancements in the EKM technology. Writing in Nature Sustainability, Wang et al.5 present the successful industrial-scale application of the EKM technology to a 5,000-ton IAD ore in South China, assisted by their additional, newly developed techniques, including the development of a new conductive plastic electrode (CPE), the design of a voltage gradient barrier (VGB) for anti-seepage, and the invention of an intermittent power alternation (IPA) strategy for energy saving. The industrial-scale experimental results indicate over 95% REE recovery efficiency, an 80% reduction in leaching agent use, a 70% decrease in mining time, and a 95% drop in ammonia nitrogen emission. This breakthrough generally overcomes key technical barriers to the large-scale deployment of EKM, marking a significant milestone with its first industrial-scale trial.