In Ukrainian

Abstract

Templated sol-gel synthesis of MCM-41‑type mesoporous silicas was realized in the presence of azo dyes (alizarin yellow and methyl red) as co-templates and silanes obtained on their basis as structure-forming components. It has been found from the results of low-temperature adsorption-desorption of nitrogen that using of azo dyes and dye-containing silanes in sol-gel synthesis leads to the substantial increase of surface area and total pore volume, and decrease of pore diameter of obtained mesoporous organosilicas. The X-ray diffraction analysis proved formation of hexagonally arranged structure of mesopores in synthesized organosilicas. It has been demonstrated due to visualization of mesoporous structure by transmission electron microscopy that all synthesized materials have hexagonally arranged structure of cylindrical pores, entrances to which are oriented outside of particles that provide accessibility of functional groups for sorbate molecules. Obtained organosilicas of MCM-41 type were used in study of dyes sorption from diluted phosphate buffer solutions as dependent on their equilibrium concentration, pH of medium, and duration of contact. It has been found that the most efficient sorption of alizarin yellow takes place at рН ~ 3 and methyl red at рН = 2.5-5.0. Analysis of kinetic curves carried out using Lagergren, Ho‑McKey, and Weber-Morris models has shown that process of azo dyes sorption by organosilicas is described by kinetic model of pseudo‑second order. The parameters of equilibrium sorption of alizarin yellow and methyl red on organosilicas of MCM‑41 type were calculated using Langmuir, Freundlich, Redlich‑Peterson, and Brunauer‑Emmett‑Teller models. Sorption of a number of acid dyes from their individual solutions was studied at pH 4.8. It has been found that chemical immobilization of methyl red on silica surface causes increase of acid dyes sorption. The contribution of cooperative interactions, which arise between the aromatic groups of azo dyes immobilized in surface layer of silica and dye molecules in a solution, in the process of their sorption was confirmed. Modification of silica surface with capable to self-aggregation dyes is a promising way in chemical design of sorption-active materials.