Studies on inorganic ion exchangers. Fundamental properties and application in nuclear energy programmes

Investigations on inorganic ion exchangers have been carried out with a view to understand the fundamental properties and to assess their suitability in specific applications in the Nuclear Fuel Cycle. Method of preparation had a marked influence on the structure and properties of this class of materials, as in the case of crystalline thorium arsenate (TA) and hydrous oxides, especially hydrous titanium oxide (HTiO). The new crystalline modifications of TA, in contrast to the monohydrate, exchanged larger ions like Na+, K+ in addition to Li+, due to the large interlayer spacings. Hysteresis in H+-Li+ exchange was observed. The selectivity sequences for alkali, alkaline earth and transition metal ions on hydrous thorium oxide (HThO) and magnetite (MAG) were similar to those observed for other hydrous oxides. While hysteresis in anion exchange involving uni-univalent anions on HThO was observed, cation exchange reactions involving Ca2+ and Cu2+ were found to be non-reversible. Preliminary investigations on the usefulness of hydrous oxides in the recovery of uranium from sea water, and purification of reactor coolant water are reported in this paper. Different hydrous oxides having varying acidities were screened for their uranium sorption capacities. On HTiO, the most promising adsorbent among the hydrous oxides, the influence of anions on the sorption of uranium, the possible mechanism of sorption of uranium from carborate solutions and under simulated sea water conditions were studied. Investigations on the sorption of cationic corrosion products on hydrous zirconium oxide (HZrO), HThO and MAG up to 363 K and of anions on mixed oxides, like Bi(III)-Th(IV) mixed oxides, from alkaline solutions were carried out with a view to test their utility in reactor coolant water purification systems