Абстрактный

Separation of cerium, light and heavy rare earth concentrates from Egyptian crude monazite

Osama S.Helaly, Mohamed S.Abd El-Ghany, Emad H.Borai,Hisham F.Aly, Tarek M.Abdel Fattah

Laboratory-scale experimentswere conducted to recover cerium, light and heavy rare earth elements fromEgyptianmonazite in sulfuric acid medium. The method includes acid leaching of Egyptian monazite and subsequent aqueousmedia extraction of the leached metals into two successive stages. Rare earth double sulfate selective precipitation was carried out upon the two leach solutions to prepare concentrates containing most of the light rare earth elements. Light rare earth double sulfate concentrates were conversed to hydroxide then filtration, washing and drying at 180oC for 10 hrs were used to oxidize Ce3+ to Ce4+. Light rare earth hydroxide cakes were leached with dilute nitric acid under pH control of 3.0 to leach most of the trivalent rare earth elements rather than Ce4+ which left as high cerium concentrate. The leach solution containing light and other trivalent rare earth elements was precipitated successively at pH values of 7.5, 8.5 and 9.5. Cerium concentrates contained 47 – 48% CeO and the light rare earth concentrate precipitated at pH 7.5 containedmore than 64%La,Nd, Pr and Sm oxides. Solutions after the double sulfate precipitation were subjected to thorium separation at pH 1.1 then the resultant clear solution was thoroughly neutralized at pH 6.5 where the precipitate slurry was converted to hydroxide. The produced hydroxide cake was leached with HCl at pH 3.0 and the leach solution was selectively precipitated using oxalic acid to produce the first oxalate concentrate which was composed mainly from yttrium(about 18%Y2O3).