Nanocomposites and nanomaterials

Kinetic and equilibrium studies for the sorption of benzene and phenol from water on functional MCM-41 silicas
I.M. Trofymchuk, N.V. Roik, L.O. Belyakova
Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17 General Naumov Str., 03164 Kyiv, Ukraine. 
E-mail: trofymchuk_iryna@ukr.net

Mobile crystalline materials (MCM-41) are ordered silicas synthesized via liquid crystal templating mechanism by subsequent removal of the organic template using calcination or acid dissolution [1]. High surface area, regular channel type structures, large pore volume and diameter, excellent hydrothermal, thermal and hydrolytic stabilities, active silanol groups on the surface of MCM-41 silicas make them an interesting alternative to the usage of popular available sorbents (carbon and polymeric materials) for aromatic compounds removal. Moreover, to increase the efficiency of sorption on MCM-41 in water treatment processes it is possible to modify the surface of silica with highly active and/or selective groups.
In the present work, supramolecular approach of the synthesis of MCM-41 silicas with oligosaccharide units was used for obtaining nanoporous materials with high affinity to aromatic compounds in aqueous solutions. Here, the unique ability of β-cyclodextrin (β-CD) to form inclusion complexes with different compounds, combined with hexagonally ordered mesoporous structure of silicas, offers attractive opportunities. MCM-41 silicas with different content of β-CD-containing functional groups were synthesized by sol-gel co-condensation of silane precursors in the presence of ionic surfactant as template. To elucidate the contribution of oligosaccharide units as supramolecular centers into the properties of synthesized materials, the removal of benzene and phenol from aqueous solutions by pristine MCM-41, amino- and β-CD-functionalized MCM-41 silicas was conducted. Multibatch sorption tests were carried out at room temperature to examine the efficiency of synthesized silicas toward aromatics’ uptake from water depending on time and equilibrium concentration. Typical kinetic and isotherm adsorption models were used to analyze the sorption processes on synthesized silicas. Prepared MCM-41 silicas demonstrate stronger affinity towards benzene than to phenol that could be very promising for selective removing of hazardous compounds in water treatment processes.

1.	Kresge C., Leonowicz E., Roth W., Vartuli J.,Back J. Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism // Nature.-1992.-359-P. 710-712.