Dissolution of Aluminum-, Titanium-, and Zirconium-Based Crystalline Waste Form Components Under Hydrothermal Conditions

Effect of synthesis conditions for phosphated mesoporous zirconium dioxide on formation of its structure and adsorption properties

“…According to the data in [10], the distance between oxygen atoms in the SO 4 2− tetrahedral anion is 2.52 Å. We find the Zr atoms at approximately the same distance, and consequently also the OH groups bonded to them on the surface of amorphous hydrated zirconium oxide.…”

“…Breakdown of the mesophase was connected by the authors of [3] with incomplete condensation of the framework former and the occurrence of oxidation-reduction reactions during detemplating, and also with some characteristic intrinsic features. In particular, synthesis of MMSs based on ZrO 2 is complicated by the low solubility in water and the phase transformations at a temperature above 300°C [4]. A major problem in template synthesis of ZrO 2 , as for other transition metal oxides, is 0040-5760/06/4201-0053…”

“…However, we must note that the hexagonal structure is formed at pH 2 and 6 ( Fig. 1b, curves 1, 2) and only when ammonium sulfate is added to the reaction mixture, which is connected with the fact that sulfate complexes of zirconium are more stable than chloride complexes [8], and the presence of SO 4 2− groups in the system promotes structure formation according to an S + X -I + mechanism. At pH 9, as in the previous case, no spatial organization is observed.…”

“…This possibly occurs due to the relatively low degree of condensation of the hydroxyl groups. The preparation method used in this work calls for the use of a buffer SO 4 2− anion between the positively charged complex of zirconium and the surfactant cation. However, the presence of sulfate groups is not enough to prevent breakdown of the structure when the template is removed at 500°C.…”