Solvent extraction, speciation, separation and recovery of uranium(VI) from nuclear fuel, phosphate rocks and monazite sand with N-phenylbenzo-18-crown-6-hydroxamic acid

A method for solvent extraction, separation and recovery of uranium was developed using a new reagent, N-phenylbenzo-18-crown-6-hydroxamic (PBCHA) in the presence of cerium, thorium and lanthanides. Uranium was extracted with a dichloromethane solution of PBCHA producing an orange coloured complex at l(max) = 400 nm with a molar absorptivity of 5.0(.)10(4) l(.)mol(-1) (.) cm(-1) and which obeyed Beer's Law in the range of 0.48-5.76 ppm. For ICP-AES the extract was directly introduced into the plasma to enhance the sensitivity several folds with a detection limit of 0.5 ppb. The extraction constants of uranium crown hydroxamic acid complexes were also determined. The selectivity factors K-uranyl(b(2)K/K or b(2)K'(e)/K) for uranium crown hydroxamate were evaluated by comparing the K-uranyl with the stability constants of competing metal cations (K) and anions (K) and were found remarkably large. Uranium was recovered in 99.95% purity from monazite sand and phosphate rocks. It could be also preconcentrated and determined in environmental samples.