Yoshio Takahaski, a professor of environmental chemistry at Hiroshima University, said a research team—which also includes Japan's Aisin Cosmos R&D Co. Ltd.—has determined that dried salmon milt or sperm is a "low-cost and environment-friendly" method to extract rare earth metals.
The announcement of the research team's findings was made at the Japan Sustainable Mining, Investment and Technology Business Forum in Tokyo and reported by Kyodo News.
The research team, based in Aichi Prefecture, found a 2010 study which determined phosphate groups found on the surface of bacteria can absorb and separate rare earths from the ore 10 times more effectively than the current extraction and separation REE process with extraction resin. The team then decided to explore the possibility of using milt—rich in phosphoric acids, but usually thrown away—for rare earth element extraction.
The team performed an experiment in which salmon milt was dried, powdered and put into a beaker containing a rare earth metals solution. The milt absorbed the rare earth elements as well as bacteria do, particularly the scarce and very expensive elements thulium and lutetium.
Unlike bacteria, milt does not have to be cultivated and is easier to preserve in a powdered state.
The team also believes that by making more use of milt through different chemicals, it can extract various types of rare earths.