Polymethylenebis(Octylarsinic acids), [C8H17As(O)OH] 2 (CH2)sub(n), as reagents for the liquid-liquid extraction of cerium(III) and europium(III)

Cerium(III) and europium(III) are extracted at 500C by [C 8H17As(O)OH]2(CH2)sub(n) (n=6,8,12) in n-octanol from aqueous solutions containing NaCl and acetic acid/sodium acetate in the pH range 6.7-8.0. The extraction coefficient, Esub(α)0, reached a maximum of: 10.0, 13.2 for n=6; 10.7, 20.0 for n=8; 4.68, 6.03 for n=12; at an aqueous equilibrium pH of: 7.65, 7.80 for n=6; 7.89, 7.95 for n=8; 7.81, 7.82 for n=12; corresponding to the extraction efficiency of: 91%, 93% for n=6; 92%, 95% for n=8; 80%, 83% for n=12; for cerium and europium respectively. The long Esub(α)0 was found to be second power dependent for cerium and one and one-half power dependent for europium on the negative log of the aqueous equilibrium [H+] for n=6, 8, 12. The extractions were done at 500C using organic reagent solutions (1.09 x 10 -3 M for n=12, 1.08 x 10-3 M for n=8, 1.32 x 10-3 M for n=6) and aqueous solutions of 1.0 x 10-5 M for CeCl3 and EuCl3, having their Clsup(-) ionic strengths adjusted to 0.100 molar with NaCl. It was found that the slopes increase in the pH dependence studies in the series n=6, 8 and 12 for both cerium and europium metal ions. The reagent dependence studies were done at 500C and pH: 7.00, 6.80 for n=6; 7.30, 7.20 for n=8; 7.45, 7.35 for n=12; for cerium and europium, respectively. The log Esub(α)0 was found to be first power dependent on the log of the uncomplexed reagent concentration at equilibrium. It is assumed that the complexes are hexacoordinated. (Author)