Chinese Academy of Sciences
Assembly Line
⛏️ Industrial-scale sustainable rare earth mining enabled by electrokinetics
Owing to their irreplaceable role in several essential technologies, rare earth elements (REEs) are critical raw materials for the global economy. However, the supply of REEs raises serious sustainability concerns due to the large environmental footprint of conventional mining processes. We previously proposed an electrokinetic mining (EKM) technique that could enable green and selective extraction of REEs from ores. Here we further develop this technique to industrial scale by addressing challenges related to electrode reliability and flow leakage and evaluate its mining efficiency, environmental footprint and economic performance. Moreover, a voltage gradient barrier strategy based on electroosmosis is developed to facilitate electrokinetic REEs mining. As a result, we successfully achieved a high REE recovery efficiency of 95% on a 5,000-ton REEs ore. A rigorous environmental risk assessment revealed a 95% reduction of ammonia emissions, indicating a notably reduced environmental footprint. A comparative technoeconomic analysis between the conventional and the EKM techniques demonstrates the economic viability of the EKM technique. This work validates a new sustainable path for REEs mining, paving the way to a greener resources supply.
A compact elastocaloric refrigerator
Elastocaloric cooling is regarded as one of the most promising cutting-edge alternatives to conventional vapor compression refrigeration systems. This technology is based on the temperature change of materials when being subjected to uniaxial stress, which has been observed in polymers, alloys, and ceramics. However, the existing elastocaloric prototypes have a bottleneck problem of an excessive mass ratio between the actuator and the solid-state refrigerant. To overcome this challenge, this study proposes an elastocaloric refrigerator using a single actuator with an inclined angle to produce a vertical tensile force to nickel-titanium (NiTi) shape-memory wires and a lateral motion to translate the NiTi wires between the hot and cold sides. The refrigerator can achieve a 90% improvement in the mass ratio between the solid-state refrigerant and actuator compared to the currently best-reported elastocaloric cooling prototype. The NiTi wires exhibit an adiabatic temperature change of 6.6 K during unloading at the strain of 4.8%. The proposed refrigerator can achieve a 9.2-K temperature span when the heat source and sink are insulated from ambient and has a cooling power up to 3.1 W under zero-temperature-span condition. By using thinner NiTi wires or NiTi plates, the developed elastocaloric refrigerator could be a starting point to promote applications of this technology in the future.