Abstract: The synergistic extraction of La(Ⅲ)and Dy(Ⅲ)from nitrate medium with 1,9-bis(1'-phenyl-3'-methyl-5'-oxopyrazol-4'-yl)nonanedione(BPMPND or H₂A)and trioctylphosphine oxide(TOPO or B)in chloroform has been studied at 25℃. Method of constant molarity was used to study the synergistic effect. The acidic synergistic extraction coefficient and the synergistic extraction coefficient of La(Ⅲ)and Dy(Ⅲ)were calculated. By using slope analysis method, the compositions of the synergistic extracted species have been shown to be LaA·HA·B and DyA·HA·B and their synergistic extraction equilibrium constants were determined. The influence of temperature on the synergistic extraction distribution ratio was studied in extraction of dysprosium(Ⅲ). The solid synergistic species were obtained and their compositions have been analyzed and explored through elemental analysis, IR, TG and DTA.

Key words: bis(phenyl-methyl-oxypyrasol)nonanedione, trioctylphosphine oxide, lanthanum, dysprosium, synergistic extraction