Synthesis, characterization and adsorption performance of functionalized mesoporous organosilicas

Functionalized mesoporous silicas are potentially effective materials in water remediation processes due to their high surface area, controllable and definite porosity, and surface modifiability. In this study, mesoporous silica (MS) was synthesized via template assisted technique and modified with 3‒(chloropropyl)trimethoxysilane. Three different functionalized mesoporous organosilicas were obtained by post modification of the chloropropyl functionalized activated MS with N,N‒dimethyloctylamine, N,N‒dimethylbenzylamine, and 1,6‒diaminohexane. The silicas were characterized by elemental analysis, SAXS, TGA, FTIR, BET surface analysis, wetting and contact angle measurements. The results confirmed the mesoporous structure of the materials and the success of the modification of MS with organic functional groups. The adsorption performance of the organosilicas were investigated for a textile dye of Acid Orange 8 (AO8) from aqueous solutions with respect to solution pH, contact time, initial dye concentration and temperature. The results showed that functionalized organosilicas have adsorption abilities much higher than unmodified MS. Maximum adsorption capacities were obtained at pH 2 and 20℃. AO8 adsorption was fitted to the pseudo‒second‒order kinetic model, and Freundlich isotherm model for each adsorbent. Thermodynamic parameters indicated that the adsorption process is physical in nature, exothermic, and spontaneous at 20°C. It is concluded that the functionalized mesoporous organosilicas synthesized in this work can be potential adsorbents for the removal of organic pollutants from wastewater.