The extraction of uranium from seawater by poly(amidoxime)/poly(hydroxamic acid) resins and fibre

Abstract

The uranium concentration in seawater is 3 μg/l with an estimated 5 × 10 9 tonnes of uranium in the oceans, in solution as the tricarbonato complex. Any extraction process will encounter the problems attendant on this high dilution, the only feasible methods currently being ion exchange on chelating resins or sorption onto inorganic materials. Poly(amidoxime)/poly(hydroxamic acid) chelating resin has been produced with high uranium sorption from neutral solutions containing the metal as the tricarbonato complex, and the results of a study of the behaviour of this resin towards seawater are given. High chemical and biochemical stability and fast sorption kinetics are properties of the resin which can sorb 68 per cent of the uranium present using a 24 s resin to seawater contact time. Poly(amidoxime)/poly(hydroxamic acid) fibre, prepared by the oximation of poly(acrylonitrile) fibre, is able to sorb 12.5 per cent of uranium in seawater with a 2 s contact time and has the advantage of being in a form capable of weaving into a chelating cloth. Sorbing 1.8 mg uranium per gramme fibre per 10 days, the cloth can be produced as an endless belt, for a continuous process for uranium extraction. A theoretical model indicates that uranium production could be possible at 6 tonnes per annum.