Raising rare earth recovery with yeast

While not quite as easy as whipping up a science experiment in the kitchen, a research group from the Osaka Metropolitan University Graduate School of Engineering has developed an inexpensive and eco-friendly way to condense various rare earth elements (REEs) from natural water sources using common, food-safe ingredients.

The research group, led by Professor Masayuki Azuma and Associate Professor Yoshihiro Ojima, have successfully tested an adsorbent material using dry baker's yeast and trimetaphosphate (a food additive) to selectively recover REEs from mineral-rich hot springs and seawater.

The phosphorylated yeast, abbreviated p-yeast, can readily be utilized as a material for recovering useful metals and removing toxins, potentially ensuring a cheap and environmentally sustainable supply of trace elements vital to the energy transition.

This discovery can reduce costs of recycling electronics and electric vehicle batteries as well as improve efficiency in recovering REEs from various mine tailings and filtering REEs from brines used by tandem geothermal power plant and mineral mining processes.

In experiments using synthetic seawater containing dysprosium and ytterbium, 90% of the ions were adsorbed while the high concentrations of sodium and magnesium present were left behind. The performance of p-yeast was also tested using strongly acidic water from the Tamagawa Onsen Obuki hot spring in Akita Prefecture, Japan containing several tens of parts per billion of naturally occurring rare earths, namely, lanthanum, cerium, and gadolinium.

In additional tests, aluminum and ferrous (iron) ions present at high concentrations were partially removed as a precipitate after pH adjustment while 60%–80% of the various REEs remained in the solution.

Adding to its overall sustainability, p-yeast can be produced from surplus yeast, otherwise designated as industrial waste, and may also prove to be a practical microbial adsorbent, with further uses promised by additional research already in the works.

The team is far from finished, citing their commitment to further research and development in pursuit of sustainable and effective metal resource management. Future avenues of study involve experiments on additional environmental water samples, ultimately establishing an optimized, scalable system for treating large volumes of metal-rich liquid resources through continuous operation.

The complete results have been published in the journal Environmental Technology & Innovation.

"This new technology is expected to contribute to the realization of a metal resource-circulating society and a safe society through environmental purification. In the future, we will continue to conduct experiments on a variety of environmental water with the aim of establishing a system capable of treating large quantities of metal resources through continuous operation." said Azuma.