Hyree-phase extraction study of cyanex 923-n-heptane/Ce~(4+)-H_2SO_4 system

摘要

Phase behavior of the extraction system,Cyanex 923-heptane/Ce~(4+)-H_2SO_4 has been studied and compared with Cyanex 923-heptane/H_2SO_4 system.Cerium(IV)is mainly extracted into the third phase,and its concentation in the third phase first increases with 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.Thd acid concentration increase 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 characteristic lamellar stucture formed by the aggregates of Cyanex 923·(H_2SO_4)_2·H_2O as those in the case of acid system.The third phase loaded Ce(IV) has been used to prepare ultrafine CeO_2 powder conveniently by precipitation withoxalic acid,and powders with size mostly smaller than 100nm can be obtained.