Doubly Sustainable Research Success in Recovering Critical Raw Materials

Related Vendor

Wuxi InfiMotion Technology Co., Ltd.

Electrolyzers produce hydrogen. However, they also contain important materials that are worth recovering. This is now working very well ...

Hydrogen plays a central role in the energy transition. It is obtained from water by electrolyzers using electricity, breaking it down into its chemical components. When electricity from renewable energy sources is used, what is known as green hydrogen is produced, which is considered particularly sustainable. However, this cannot be done without critical raw materials, such as platinum, rare earths, or nickel, which serve as catalysts, as researchers from the Helmholtz Institute Freiberg (HIF) for Resource Technology explain. However, it is emphasized that the experts were now able to recover these functional materials using the flotation process and liquid-liquid particle extraction—number two in the sustainability double.

Two Types of Electrolyzers in Focus

Various methods are available for hydrogen production. One possibility is water electrolysis, which was briefly described above. The catalysts needed for this in the electrolyzer consist of critical metals—the so-called functional materials. In proton exchange membrane electrolyzers (PEM), metals from the platinum group, such as platinum, iridium, and palladium, are primarily used. The second possibility utilizes high-temperature electrolyzers, which require rare earths and nickel. However, it is crucial to secure these critical raw materials, as their primary sources are in China. This is an endeavor that researchers at the HIF, under the leadership of TU Bergakademie Freiberg, are dedicating to in the "ReNaRe" (Recycling—Sustainable Resource Use) project. Since these types of electrolyzers are easy to disassemble, the researchers are working on both types. There are two processes to recover the respective catalyst materials...

This is how Valuable Raw Materials are Recovered

For the recovery of functional materials, the experts employ fine particle separation techniques. As noted, the critical anode and cathode materials are present as fine particles, approximately the size of one-hundredth of a human hair. The liquid-liquid particle extraction and agglomeration flotation have proven effective for separating the functional materials. A sustainable solvent-water cycle system is used for the extraction of these ultra-fine particles to effectively separate hydrophobic (water-repellent) cathode and hydrophilic (water-attracting) anode catalysts. In the complementary agglomeration flotation, a sustainable hydrophobic binder plays the main role in enabling the aggregation of particles into a uniform mass. The binder is an emulsion, an oil-water mixture with a very high water content, used to selectively agglomerate hydrophobic particles. With both methods, the researchers were able to recover up to 90 percent of the critical functional materials and return them to the recycling loop.