| Based on the results described in Part 1, 2 and 3, the optimum condition for recovering thorium and so-called rare earths from Korean monazite was determined, using a horizontal tube electric furnace. When the monazite was decomposed with chlorine at 700℃ using the -200 mesh monazite and charcoal respectively, the weight ratio of charcoal to monazite 0.2, the size of briquette 6-10 mesh, and a chlorine flow race 430cc/min, thorium and so-called rare earths were obtained with high recovery. And it was observed that chlorides of thorium and Yttrium may be selectively volatilized, when the monazite was decomposed at about 900℃. With the mixed oxides of thorium and so-called rare earths obtained by wet process from the chlorides prepared by chlorination of the monazite at 700℃, selective separation of the values was examined by chlorination method. The results showed that lanthanum, cerium and thorium were selectively separated to an extent by the chlorination at about 200℃. |
|
