Cyclodextin-silica nanomaterials for aromatics removal from aqueous media: kinetic and equilibrium studies

The application of nanotechnologies to remove toxic pollutants from water has been intensified during last decades. Nanomaterials could exhibit a unique physicochemical, mechanical, and biological properties. In this work, one-pot synthesis approach was used to obtain organosilica materials with nano-scale pore ordering and chemically immobilized oligosaccharide units possessing high affinity to benzene and its derivatives in aqueous solutions. To clarify the contribution of macrocycle fragments as surface supramolecular centers into the sorption properties of synthesized organosilica nanomaterials, the removal of benzene and phenol from aqueous media by unmodified MCM-41 silicas and organosilicas was conducted. Multibatch experiments were performed at room temperature to study sorption ability of synthesized silica nanomaterials with respect to aromatics in aqueous solutions depending on time and equilibrium concentration. Linear regression analysis as well as nonlinear method were applied to calculate the kinetic models’ parameters. It was found that pseudo-second-order and Elovich kinetic models are the most appropriate to describe the process of benzene and phenol sorption on β-cyclodextrin-functionalized MCM-41 silicas with 0.14–0.21 μmol/m² content of surface oligosaccharide groups. Langmuir, Freundlich, and Redlich-Peterson models were applied for experimental results to simulate the equilibrium sorption processes on synthesized nanomaterials. The close values of determination coefficients estimated by these models indicate the ambiguous character of aromatics sorption on the surface of functionalized MCM-41 silicas due to different supramolecular interaction (host–guest, hydrogen bonding, and π–π stacking). Prepared cyclodextin-silica sorbents show stronger affinity toward benzene than phenol that could be very perspective for selective removal of organic pollutants in water treatment processes.