THE INFLUENCE OF MECHANICAL PROCESSING ON THE STRUCTURE AND SORPTION PROPERTIES OF TITANIUM CONTAINING A SORBENT IN THE SORPTION OF URANIUM FROM SOLUTIONS MODELING COMPOSITIONS OF SEAWATER

Abstract

The infl uence of mechanical processing of sorbent Thermoxide-5 on its sorption properties, containing 6.2 weight % ZrO2, during extraction of uranium from solutions modeling compositions of seawater. The effect of the non-equilibrium disorder of the crystal lattice of the sorbent while using newly milled fi ne fractions (in the shape of peaks on kinetic curves) which disappear upon the expiration of a certain time was found. The values of activation energy and effective diffusion coeffi cients of defects in Thermoxide-5 at different temperatures were calculated according to obtained results of the sorption kinetics. It was established that the reason for the appearance of typical sorption peaks on kinetic dependences curves of uranium sorption by newly milled Thermoxide-5 is sharp increase of sorption rates which is related to the rearrangement of structure in the moment of phase transition. Based on XRD results it was determined that: • Diffractgram of hydrated TiO2 in primary sorbent is, particularly, in anatase modifi cation with small mixture of rutile. • Diffractogram of a newly milled Thermoxide-5 (graining ~2.2·10–3 sm) strongly blurred with weak refl exes points to the considerable amorphization (disorder) of primary structure of a sorbent. • Diffractogram of a milled sample which was kept 3 days at 22 oС temperature is identical to diffractogram of a primary sorbent and has similar refl exes of peaks, which points to practically full reduction of a crystalline structure of a milled sorbent which was kept at room temperature three days. By this way, the study of sorption kinetics of uranium on newly milled and kept or heated (annealed) samples of a sorbent Thermoxide-5 showed that in sorption process of uranium from solutions with рН 7.85 thermodynamic equilibrium can be really achieved, but intensive grinding of sorbents leads to the destabilization of their structures. In the stabilization process of the structure of a sorbent during its heating or dwelling full reduction of sorption properties occurs. Consequently, disorder of the structure of a sorbent Thermoxide-5 which is conditioned by the introduction of a isomorphic mixture of zirconium oxide to anatase lattice of hydrated titanium oxide, is thermally stable.

Keywords

• uranium
• titanium dioxide
• sorbent
• disorder of structure
• sorption
• XRD method.