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

Abstract

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 lmax = 400 nm with a molar absorptivity of 5.0 . 104 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 Kuranyl(b2K/K or b2K'e/K) for uranium crown hydroxamate were evaluated by comparing the Kuranyl 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.