Extraction of uranium from non-complexing medium in chloroform using polymethylene bis-(acylpyrazolols) as extractants

The extraction of UO22+ with the extractant α,ω-bis-(1′-phenyl-3′-methyl-5′-hydroxy-pyrazol-4′-oyl) alkane, ‘HL-n-LH’ with n, number of methylene ---CH2--- links, HL-4-LH (with a short polymethylene chain), has been described for a wide range of solution concentration at acid pH and compared to its extraction with HL-8-LH (with a long polymethylene chain). The efficient extraction of uranium (10−3 M) from its aqueous acid solution was prevented by the appearance of a third phase and loss of uranium with the shorter chain length HL-4-LH. The results demonstrated a non quantitative distribution which is not found with HL-8-LH, in the same experimental conditions. The aim of this work is to make a contribution by trying to solve the third phase problem. The very low detection limits of energy dispersive X-ray fluorescence (EDXRF) allowed dilutions, by using the concentration range 4×10−3–2×10−2 M for HL-4-LH in CHCl3 as organic phase and [UO22+]=10−4 M from perchlorate medium (Na, H)+C1O4− 1 M as aqueous phase and the titration of aqueous and organic extraction phases, for the systems UO22+, (Na, H)+CIO4− 1 M, aqueous/HL-4-LH, diluent, was performed adequately. The extraction efficiency of uranium for HL-8-LH was better across the concentration range 0.5×10−2–4×10−2 M at low pH than for HL-4-LH. The extracted complexes were UO2(L-4-LH)2, [UO2(L-4-L)]2, UO2(L-8-L), UO2(L-8-LH)2, [UO2(L-8-L)]2.