Removal of Zirconium, Iron and Aluminum Impurities from Scandium-Containing Solutions.

A study is made of the process of hydrolytic precipitation of basic zirconium sulfate for the purpose of removing zirconium impurities from scandium-containing hydrochloric solutions. It is established that the degree of removal depends on the final acidity of the solution. Practically complete removal is achieved at a final acidity of 1-2 g/liter HCl. A study is made of the behavior of scandium during the precipitation of its hydroxide from pure solutions. Upon neutralization with 5% ammonia precipitation of scandium begins at pH equals 5. 0 and ends at pH equals 7. 5. A study is made of the behavior of scandium during the precipitation of its hydroxide from commercial solutions. It is established that in the presence of zirconium, iron and aluminum impurities scandium begins to precipitate at pH equals 3. 5. The maximum quantity of impurities passes into the hydroxide precipitate at pH equals 4. 5. It is recommended that prior precipitation of Zn, Fe and Al be carried out at pH equals 4. 5 in order to reduce their concentration in the mother liquor, from which the scandium hydroxide must be separated out at pH equals 8. 0.