الفهرس 
Mesoporous materialsOnly 14 pages are availabe for public view
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Abstract
β-CD functionalized mesoporous silica KIT-6 with uniform mesopore channels via post-grafting method as an efficient adsorbent for MB dye from aqueous solutions was successfully synthesized. After functionalization, however the surface area and total pore volume were drastically decreased, the presence of β-CD active groups grafted the inner and outer pore surfaces facilitated a high molecular diffusion of MB molecules inside the mesopores with high adsorption capabilities, compared with unmodified KIT-6. The kinetic and isotherm models for both β-CDKIT- 6 unmodified KIT-6 were carefully calculated and discussed and the adsorption behavior obeyed pseudo-second-order kinetic and Langmuir isotherm models. from the thermodynamic studies, the adsorption process was exothermic and spontaneous. The adsorption capacity of MB day was highly sensitive to pH media. This study represents an example for using functionalized mesoporous silica β-CD-KIT-6 with a 3D mesostructure, which will have the potential benefit of having improved access of guest molecules to the binding sites for practical environmental applications Mesoporous materials are porous in nature with pore diameters between 2 and 50 nm. They exhibited large surface area, large pore volume and high mechanical and thermal stability. The structural capabilities at the scale of a few nanometers and high surface area for mesoporous materials can meet the demands of the growing applications such as adsorption, separation, catalysis, drug delivery, sensors, photonics, energy storage and conversion, and nano devices, especially for dealing with large molecules such as biomolecules and heavy oils. In the present thesis, mesoporous silica KIT-6 was successfully functionalized with active β-cyclodextrin groups. After carefull characterizations, a rapid QCM sensor coated with thin layers of mesoporous KIT-6 silica was designed via simple drop-coating approach for monitoring of a wide range of chemical organic vapors, such as aliphatic alcohols, amines and BTEX, such as benzene and toluene. Interestingly, the designed sensor showed a selective affinity towards basic amine compounds vapors. To realize an efficient adsorbent for water treatment, surface functionalization of mesoporous silica KIT-6 with β-cyclodextrin (β-CD) was occured via post-grafting method as a new mesoporous adsorbent for the environmental remediation of methylene blue (MB) dye from aqueous solutions. The Ph.D. thesis comprises of three chapters as follows: The first chapter: The first chapter gives an introduction about mesoporous materials, especially, mesoporous silica, previous synthetic procedures underlying the formation mechanism, development of mesoporous silica and surface modification with active organic functional groups are presented with emphasis on their recent important progress and their potential uses in varieties of applications. As well, this chapter is included a brief summary about cyclodextrins and their functionalization, especially of mesoporous silica material. Additionally, previous studies related to β-CD were also cited in this field. The second chapter: The second chapter describes the experimental part that includes the used chemicals and their sources, the practical procedures for the synthesis of mesoporous silica KIT-6 and its functionalization with polysaccharide, β-CD active groups. The preparation of toxic MB dye concentrations, buffer solutions used in the study is included, as well. In this chapter, deposition of the mesoporous silica KIT-6 layers onto the Au-electrode of QCM and experimental measurements setup is described in details. Description about the characterization techniques that were used to characteriz the mesoporous silica KIT-6 before and after functionalization is existed in this chapter . The third chapter: This chapter concerns with the results and discussions and it divided into two main parts. The first part: includes the design of a rapid, selective and reproducible QCM sensor for the detection of a wide range of volatile organic compounds (VOCs) at room temperature using unmodified mesoporous silica KIT-6 thin layers for the first time to the best of our knowledge. The KIT-6 materials was successfully characterized with transmission electron microscopy (TEM), powder low-angle X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and N2 sorption isotherm. The designed sensor showed a high selectivity towards basic amine compounds vapors via host-guest interaction with silanol groups attached to acidic silica surface. The results showed an enhanced detection sensitivity and fast response of the sensor due to the 3D biconteneous cubic mesostructure ordering of the mesoporous silica KIT-6. The sensor showed a high sensitivity and the equilibrium was achieved within few seconds. The adsorption kinetics of methanol and ethanol into KIT-6 film were determined. The negative sign of Gibbs free energy for methanol and ethanol expected a spontaneous adsorption process at room temperature. The sensor shows a good reproducibility and reversibility. The second part: discusses the surface functionalization of mesoporous silica KIT-6 with the non-cytotoxic polysaccharide β-CD as an efficient mesoporous adsorbent (abbreviated as β-CD-KIT-6) for removal of toxic MB dyes from aqueous solutions. After functionalization, the material was successfully characterized with transmission electron microscopy (TEM), low-angle X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N2 sorption isotherm and thermogravimetric (TG) analysis. Even after functionalization of KIT-6 with β-CD to give β-CDKIT- 6, the mesostructured ordering was still retained and a stable mesoporous β-CD-KIT-6 was obtained without serious damage. The β-CDKIT- 6 reveals the potential utility for the adsorption of methylene blue (MB) dye (was used as a model). The adsorption of MB dye into β-CD-KIT-6 was studied using UV-visible spectroscopy. Compared with unmodified KIT-6, the functionalized β-CD-KIT-6 showed a good adsorption capacity for MB dye. The kinetic and isotherm models for both functionalized β-CD-KIT-6 and unmodified KIT-6 were carefully studied. The adsorption behavior was found to obeyed pseudo-second-order kinetic and Langmuir isotherm model. from the thermodynamic studies, the adsorption process was found to be exothermic and spontaneous. In addition, the adsorption capacity of MB dye into functionalized β-CD-KIT-6 and and unmodified KIT-6 was increased with increasing the solution pH (increasing OH- concentration), in which the surface groups may become negatively charged, which in turns enhances the adsorption affinity through electrostatic forces of attraction with the positively charged MB cations.