THREE-PHASE EXTRACTION STUDY OF CYANEX 923-n-HEPTANE/Ce⁴⁺-H₂SO₄ SYSTEM

Abstract

Phase behavior of the extraction system, Cyanex 923-heptane/Ce⁴⁺-H₂SO₄ has been studied and compared with Cyanex" 923-heptane/H₂SO₄ system. Cerium(IV) is mainly ex-tracted into the third phase, and its concentration in the third phase first increases with the increasing aqueous acid concentration, reaches maximum and then decreases. At higher acidity, cerium(IV) is hardly extracted in the third phase. The phase behavior and change of the contents of acid and water are similar to those in the acid system. The acid concentration increases with increase of the aqueous acid in the whole extraction region while the water content first decreases with it and then increases after the third phase formation. The third phase has a char"acteristic" lamellar structure formed by the aggregates of "Cyanex 923ċ(H₂SO₄)₂ċH₂O as those in the case of acid system. The third phase loaded Ce(IV) has been used to prepare ultrafine CeO₂ powder conveniently by precipitation with oxalic acid, and powders with size mostly smaller than 100 nm can be obtained.

ACKNOWLEDGMENTS

The authors wish to thank Dr. W.A. Rickelton of Cytec Canada for supplying Cyanex 923. This project was supported by the National Program entitled ‘Basic Research of Rare Earths’ (G1998061301) and National Natural Science Foundation of China (29771028, 29801004).