Inorganic sorbents, in comparison with ordinary organic ion exchangers, have higher selectivity, radiation, thermal, and chemical stability. Inorganic ion exchangers are universal materials exhibiting both cation exchange and anion exchange properties. In this work, using aluminum hydroxide (AHO) as an example, we study the possibility of expanding the range of metal oxyhydrates that can serve as the basis to produce inorganic anion-exchange materials. The properties of aluminum hydroxide largely depend on the method of its production. This phenomenon is associated with a different state of Al3+ ions in aqueous solutions during hydrolysis. Estimation of the size of the primary particles of hydrated alumina gives a value of 19 nm. The most potent effect on the structure and ion-exchange properties of aluminum hydroxide is exerted by the introduction of alloying elements into its composition. Isomorphic substitution of a part of Al(III) ions in the structure of aluminum hydroxide with ions with a higher charge (Ti(IV), Zr(IV), or W(VI)) leads to an increase in the content of exchangeable OH-groups in the resulting material. The synthesized materials are amorphous substances, to study their structure; the method of diffuse X-ray scattering was used. The Gibbsite structural motif is determined, and structural changes occurring under the influence of various factors, and synthesis conditions are analyzed. By optimizing the composition of the material, it is possible to improve its sorption characteristics significantly. AAW-0, AAZ-0, and AAT-0 anion exchangers synthesized based on hydrated aluminum oxide can be used to purify weakly acidic electrolyte solutions from anionic impurities in the dynamic mode of repeated sorptiondesorption cycles. Materials based on mixed hydrated oxides of various elements can also be used as catalyst supports. Their anion exchange properties allow a wide range to vary the number of different anions introduced into the solid phase and, accordingly, to regulate the number and state of active catalytic sites.
Inorganic Nanostructured Anion-Exchange Materials Based on Aluminum Hydroxide
