Formation of cobalt hydroxosilicate in amorphous silica matrix

Abstract

The synthesis of cobalt hydroxysilicate Co3(Si2O5)2(OH)2 in a matrix of high dispersity amorphous silica has been proposed. It is shown the formation of a hydroxosilicate, which combines coordinated silica and cobalt-oxygen polyhedrons in the overall structure, as well as the availability of surface hydroxyl groups, contribute to the preservation of a high specific surface area as is in amorphous SiO2. The hydroxosilicate also contributes to the effective manifestation of photocatalytic properties due to the presence of cobalt (2+), which has a high reactivity. As methods of synthesis of SiO2/Сo composites hydrochemical methods are used by impregnation and autoclave treatment with solution of cobalt formate of silica. The influence of the amount of introduced cobalt on the composition, structure, and properties of a composite material containing Co3(Si2O5)2(OH)2 in a SiO2 matrix has been traced. SiO2/Co composites have been tested in the hydroquinone photooxidation reaction when exposed to ultraviolet radiation. The highest degree of hydroquinone decomposition amounting to 84% in 18 hours was achieved for SiO2/Co at a molar ratio of components Co:Si = 0.01:1.

Keywords

• amorphous silica
• cobalt silicate
• hydrothermal synthesis
• mechanosynthesis
• microstructure
• photocatalysis
• hydroquinone