Nano-TiO2-SiO2 powder as inorganic support for hybrid pigment preparation

A study was made of the adsorption of three selected food dyes (C.I. Food Black 1, C.I. Food Brown 3 and C.I. Food Green 4) on the surface of an inorganic, synthetic TiO₂-SiO₂ support of anatase form. This produces new hybrid pigments having desirable physicochemical and functional properties due to the presence in their structure of the TiO₂-SiO₂ support. The process of adsorption was conducted for dye concentrations ranging from 10 to 50 mg/dm³. The physicochemical properties of the inorganic support and the resulting hybrid pigments were determined. The characterisation included determination of the dispersion and morphology of the systems (particle size distribution, SEM images), porous structure parameters (BET isotherms) and electrokinetic properties (zeta potential and electrophoretic mobility), as well as thermal stability and colorimetric parameters. The efficiency of food dye adsorption on TiO₂-SiO₂ was examined, and the degree of coverage of the inorganic support with the food dyes was also estimated based on elemental analysis results. The results were used to evaluate the quality of the functional hybrid pigments obtained using selected food dyes and TiO₂-SiO₂ support, and to determine how the adsorption efficiency is affected by the dye structure. Selected diazo food dyes were more effectively adsorbed on the surface of the synthetic TiO₂-SiO₂ support. The hybrid pigments obtained have desirable physicochemical and functional properties. The synthesised food dye/TiO₂-SiO₂ hybrids may be used in pharmaceutical products.