Removal of uranyl cations from iron-containing solutions using composite sorbents based on polymer matrix

Abstract

Some technologies of uranium recovery from minerals involve hydrochloric acid where cationic forms of uranyl ions dominate. The work is devoted to development and testing of sorbents for removal of uranium(VI) from liquid wastes containing also an excess of Fe(III) ions. Organic-inorganic ionexchangers based on gel-like strongly acidic resin containing zirconium hydrophosphate have been proposed for this purpose. The theoretical approach, which allows us to control a size of incorporated particles, has been applied to modification of the resin with the inorganic constituent. The results of TEM show that the samples contain mainly aggregates of nanoparticles (300 nm) or simultaneously aggregates (200 nm) and agglomerates (several microns). The synthesized organic-inorganic ion-exchangers contain from 10 to 50 mass. % of zirconium hydrophosphate. Composition and structure of the ion-exchangers affect their sorption properties. Sorption of U(VI) from modeling solutions containing also HCl and Fe(III) ions was researched under batch conditions. The initial pH of the solution was within the interval of 2–4, the sorbent dosage was 2–10 g/dm3. Simultaneous sorption of U(VI) and Fe(III) species was shown to occur, the removal of Fe(III) species is faster and more complete. Increasing of the sorbent dosage and the solution pH results in improvement of the efficiency of uranium (VI) removal and increase of the exchange rate. Sorption degree of uranyl cations reaches about 90 % after 3 h at pH 2 and the sorbent dosage of 10 g/dm3. When the sorbent dosage is 5 g/dm3 and the solution pH is 4 the sorption degree reaches 100 % for the composite containing 10 % of the inorganic constituent. The sorption degree is lower for the materials containing higher amount of zirconium hydrophosphate. The rate of sorption has been found to obey mainly particle diffusion model. The models of chemical reaction of pseudo-first or pseudo-second order can be also applied. The composites show mainly higher sorption capacity towards U(VI) at pH 2, the pristine resin demonstrates higher capacity towards Fe(III) under these conditions. The organic-inorganic ion-exchangers can be recommended for polishing of liquid wastes which are formed during monazite processing.