Preparation of mesoporous silica materials functionalized with various amino-ligands and investigation of adsorption performances on aromatic acids

In this study, mesoporous silica-based adsorbents functionalized with four kinds of amino groups, namely (3-aminopropyl)trimethoxysilane, trimethoxy[3-(methylamino)propyl]silane, N-[3-(trimethoxysilyl)propyl]ethylenediamine and 3-[(trimethoxysilyl)propyl]diethylenetriamine, were prepared using post-synthesis method and named as SiO2-N, SiO2-N-, SiO2-2N and SiO2-3N, respectively. Infrared spectrum, elemental analysis, water contact angle and adsorption/desorption measurements were applied to evaluate the characteristics of these materials. Five kinds of aromatic acids (gallic acid, chlorogenic acid, caffeic acid, p-coumaric acid and rosmarinic acid) were chosen as probe molecules to evaluate adsorption properties of the four adsorbents. Their adsorption performances were evaluated by two strategies of dynamic solid phase extraction (SPE) adsorption and static adsorption under individual and mixed two modes. Through a series of adsorption experiments, the results clearly illustrated adsorption capacities conformed to SiO2-N < SiO2-N- < SiO2-2N < SiO2-3N. For the five probe molecules, their adsorption amounts were affected by adsorption strategies, adsorption modes, structure-activity relationship, steric hindrance and interaction forces. By this work, it helped us to have a better understanding about adsorption processes and provided us inspirations and impossibility to develop new amino-group based adsorbents.