SEPARATION OF THORIUM FROM MONAZITE

Abstract

The fact that thorium is present in monazite in relatively small amounts and in association with larger quantities of chemically similar rare earth, clements makes its separation a matter of considerable difficulty. A method which is often used in separating thorium from the rare earths in acid solutions of monazite is based on the fact that thorium phosphate is, much less soluble in acid solutions than the corresponding rare earth phosphates. Solutions of monazite in sulphuric acid are therefore neutralised to the requisite acidity for the precipitation of thorium phosphate either by dilution with large quantities of water or by adding magnesia, ammonia or sodium hydroxide. A study of the exact conditions under which ammonia can be used in an effective separation has been made and the results are embodied in the present paper. Pure Travancore monazite which has been freed from zircon, rutile and siliceous impurities was used in these investigations.