Adsorption of the selected organic dyes on the functionalized surface of precipitated silica via emulsion route

Abstract

Physicochemical analysis was performed on silicas precipitated according to a novel method, in an emulsion system. Substrates for the process involved solutions of sodium metasilicate and sulphuric acid while the organic phase consisted of cyclohexane and non-ionic emulsifiers. The silicas were used to obtain hybrid structures of the formed inorganic pigments. For this purpose, the adsorption of organic dyes on the silica surface was preceded by modification of the surface with silane coupling agent containing amine groups. Specific surface area (BET) and porous structure of the raw silicas were estimated. The silicas and pigments were subjected to studies on surface morphology, zeta potential, particle size and distribution of particle diameters were also established. Effects of modification with the aminosilane were appraised using FTIR and 29Si CP MAS NMR techniques. Stable pigments were obtained on silica core, the surface of which was modified with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. Particles of the obtained pigment manifested a spherical shape and particle size distribution proved that no agglomerate structures were present. High stability of the obtained pigments proved that the organic dye was chemically bound to the modified silica surface. Mechanisms of inorganic–organic hybrid formation were also suggested.