Selectivity of bis[n-butyl(hydroxyl)phosphoryl]dibenzo crown ether endoreceptors in metal extraction from nitric acid solutions

Diphosphorylated dibenzo crown ethers with 4,4′(5′)-bis[n-butyl(hydroxy)]phosphoryl substituents at the benzene rings of dibenzo-18-crown-6 (I), dibenzo-21-crown-7 (II), and dibenzo-24-crown-8 (III) were prepared and studied with the aim of developing new highly effective and selective extractants for recovery and separation of metals. Extraction of a solution containing Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Li, Mg, Mn, Mo, Na, Ni, Pb, Re, Sc, Sr, Tl, V, Y, and Zn (10 ppm each) and an Am(III) solution in 0.01–5 M HNO3 with 0.05 M solutions of the endoreceptors in chloroform was studied. For endoreceptor III, the maximal distribution ratios of metals Dmmax are ranked in the following order: Sc (>103) > Am (162) > Mo (129) > V (75.9) > In (29.3) > Bi (16.5) > Fe (4.7) > Rb (1.0) > Pb (0.34) > Ga (0.18) > Ge (0.11) > Al, B, Ba, Ca, Cd, Co, Cr, Cu, K, La, Li, Mg, Mn, Na, Ni, Re, Sr, Tl, V, Zn (