Influence of aminosilane surface modification and dyes adsorption on zeta potential of spherical silica particles formed in emulsion system

Studies were performed on the synthesis of spherical silica in an emulsion system. The obtained silica was subjected to surface modification using N-2-(aminoethyl)-3-aminopropyltrimethoxysilane in order to increase adsorptive properties of the silica surface. On surfaces of the unmodified silica material and the aminosilane-functionalised silica C.I. Reactive Blue 19 and C.I. Acid Red 18 were adsorbed. The obtained silica and its derivatives were subjected to physicochemical evaluation: particle size and polydispersity were examined, specific surface area (BET) was determined, surface composition was defined using elemental analysis. The principal aim of the studies was to define electrokinetic (zeta) potential and determination of its alterations as a function of pH in all types of the tested silica colloids. For the purpose the technique of electrophoretic light scattering (ELS) was applied. Effect of ionic strength on stability of tested colloids was also examined. The tested aminosilane was found to exert critical influence on values of zeta potential and, thus, on values of isoelectric point (i.e.p.). The modified silicas reached peak stability within the pH range of 2–4 manifesting zeta potential within the range of (−20) to (−45) mV.