Structural Approach to Understanding the Formation of Amorphous Metal Hydroxides

4価金属水酸化物コロイド特性の理解に向けた熱力学的アプローチ

小林 大志*; 伏見 朋和*; 水越 寛文*; 元川 竜平   ; 佐々木 隆之*

Kobayashi, Taishi*; Fushimi, Tomokazu*; Mizukoshi, Hirofumi*; Motokawa, Ryuhei; Sasaki, Takayuki*

This study investigates the colloidal behavior of M(IV)(OH) based on its zeta potential and hierarchical structure. The zeta potentials of ZrO and ThO in NaCl, NaNO, and CaCl solutions under various pH and ionic strength conditions were measured and elucidated by a surface ionization and complexation model combined with an electric double layer. Based on the assumed similarity of the surface reactions, the model was applied to interpret the zeta potentials of Zr(OH) and Th(OH) in NaCl, NaNO, and CaCl solutions. The differences in the model parameters were deduced from the different origins of M(IV)(OH) formed by hydrolysis reactions. The size distributions of the selected Zr(OH) suspensions measured by dynamic light scattering techniques suggest that the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory governs the colloidal behavior of large aggregates. Additionally, the small angle X-ray scattering measurements elucidated the structure of Zr(OH) in the nanometer scale. The primary and secondary particle sizes were found to be more dependent on the ionic strength of the electrolyte solutions than on the zeta potentials. The direct interaction of counter ions may affect the formation of primary and secondary particles with comparable size ranges.

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