Recovering rare metals

Japanese scientists have found a way to recover rare-earth metals from seawater

Published: Saturday 15 May 1999

researchers at the Japan Atomic Energy Research Institute ( jaeri ) have developed a new material that can effectively recover rare-earth metals from seawater. Japan hardly produces rare-earth metals such as vanadium, cobalt and uranium, which have several industrial, engineering and biomedical uses. For example, vanadium is used in the aircraft industry, and cobalt in treatment of cancer. The research group that developed the substance was led by Takanobu Sugo, manager of the radiation utilisation development section of jaeri 's department of material development ( Science and Technology in Japan , Vol 18, No 69).

The research group has been studying the application of radioactive rays to polyethylene fibre (non-woven fabric) in order to develop functional materials for the selective adsorption of metals. (Adsorption is the adhering of atoms or molecules of gases, liquids or solutes to exposed surfaces, usually of solids.) The researchers conducted adsorption tests several times by anchoring the material in the sea and separating it with an acid solution. Seawater dissolves rare-earth metals such as cobalt. As the concentration of these metals is very low several milligrammes per one tonne of seawater it has been difficult to develop technology to recover these metals at an economical cost.

The adsorbent developed at the jaeri 's Takasaki Research Laboratory is quite different from conventional ones. It has a high capability to selectively adsorb rare-earth metals, and is able to concentrate the metals in seawater by one million to 10 million times. It can also be used repeatedly because of its high stability in seawater. This discovery raises the possibility of obtaining certain rare-earth metals at an economical cost by processing seawater with this efficient adsorbent.

The scope of this substance as a new source of rare-earth metals is immense given the massive volume of rare-earth metals present in the neighbouring waters of Japan. jaeri is planning to conduct technical tests to study the possibility of developing a practical recovery system of the metals.

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