STUDYING OF THE DISSOLUTION PROCESS OF ZrO₂–Y₂O₃–CeO₂–Al₂O₃ NANOPOWDERS SYSTEM IN AQUEOUS MEDIA AT DIFFERENT pH

The paper examines nanopowders of ZrO₂–Y₂O₃–CeO₂ and ZrO₂–Y₂O₃–CeO₂–Al₂O₃ systems in order to study the influence of a dispersion medium pH on the solubility of complex nanopowder particles in aqueous media after filtration and centrifugation for preparation of stable dispersions for further toxicological tests of nanoparticles. The concentration of elements remaining in the supernatant after sample preparation which includes membrane filtration and centrifugation is determined by inductively coupled plasma optical emission spectrometry. The paper defines main characteristics of dispersions of synthesized nanopowders such as the point zero of charge and zeta potential. It is found that the highest aggregate stability of nanopowder dispersion without Al₂O₃ additive lies in the optimal pH range from 5,5 to 9,5, while the highest aggregate stability of nanopowder dispersion with Al₂O₃ additive is at pH = 7,0. The obtained results indicate that dispersion of these powders leads to formation of yttrium oxyhydroxide hydrosol dissolved at pH < 6,0. Aluminum hydroxide is formed when the powder with Al₂O₃ additive is dissolved in neutral aqueous media, while in acidic media (pH < 6) basic soluble salts are formed instead of aluminum hydroxide, and in alkaline media (pH > 7) amphoteric aluminum hydroxide is dissolved due to the formation of aluminates

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