Properties of amorphous silica as modified by adsorbed silane coupling agents and organic dyes

Two types of amorphous silica namely, the precipitated silica and the pyrogenic silica, were studied. The surfaces of such silica were modified with silane coupling agents such as 3‐aminopropyltriethoxysilane, N‐2‐(aminoethyl)‐3‐aminopropyltrimethoxysilane and 3‐ureidopropyltrimethoxysilane. Pigments were obtained by the adsorption of organic dyes, C.I. Reactive Blue 19 and C.I. Acid Green 16, onto the modified silica surface. Structural properties of the modified silica and the pigments obtained were evaluated using scanning electron microscopy, zeta potential analysis and particle size measurement techniques. Moreover, colour of the pigments obtained was evaluated using the CIE L *a*b* colour space system. The specific surface area of the pigment obtained was estimated using the BET method.