Most rare earth minerals contain uranium, thorium and their decay products, so the technology for removing radioactivity plays a key role in the production of rare earths, especially in reduction of production cost, environmental protection and application of rare earth products. Furthermore, complete removal of trace radioactive substances existing in rare earth products is highly significant for wide application of rare earths and in medicine for health protection and cure.
Up to now, many methods for separating and removing radioactive substances have been reported: ion exchange method, solvent extraction method, co-precipitation method, etc. among which co-precipitation method is very effective for infinitesimal amount of radioactive materials such as radium and actinium. In an extremely dilute system, trace radioactive substances are usually separated by co-precipitation with carriers. Porous materials such as diatomaceous earth, activated carbon, fire brick, silica gel and alumina, barium sulfate, strontium sulfate , iron hydroxide(Ⅲ) and aluminum hydroxide are used as carriers.
In an attempt to remove trace radioactive substances existing in industrially produced rare earth carbonate, Kim Chol Ju, a researcher at the Faculty of Chemical Engineering, has conducted an experimental study of the radioactivity removal characteristics of [Ba-Fe] co-precipitation method, the combination of BaSO4 and Fe(OH)3 co-precipitation methods.
In the [Ba-Fe] co-precipitation process, the total removing rate is over 92% and loss rate of rare earths is less than 0.1% in the case of industrially produced rare earth carbonate.
As this method enables prompt and effective removal of radioactive elements such as uranium, thorium, radium, radiolead, etc., remaining in extremely small quantities in rare earth compounds, it could be applied in the field of hydrometallurgy in which rare earth compounds are produced from several kinds of rare earth minerals and in other fields of production and application of rare earth materials from rare earth compounds.
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