Adsorption, nanoporous materials silica

Many applications of silica-based nanoporous materials such as adsorption, ion exchange, catalysis and sensing, require specific surface properties. Since the discovery of the MCM series of mesoporous materials [1], two main methods have been used to functionalize their large internal surface [2]. 

Compared with the traditional adsorbent such as activated carbon, zeolites, and silica gel, electrospun nanoflbers are good candidates for heavy metal ion adsorption due to its large surface area, tailored pore structure, good interconnectivity of pores, and potential to incorporate active chemistry or functionality on nanoscale [62,63]. Moreover, recycle is of great importance in the field of water treatment taking this aspect into consideration, the nanofiber-based adsorbents are more suitable compared with powdered nanoporous materials. 

Figure 1.6 Top Low-temperature nitrogen adsorption ( ) and desorption (x) isotherms measured on a calcined SBA-15 mesoporous silica solid prepared using an EO20PO70EO20 block copolymer [54]. Bottom Pore size distribution derived from the adsorption isotherm reported at the top [54]. A high surface area (850 m2/g), a uniform distribution of cylindrical nanopores (diameter —90 A), and a large pore volume (1.17 cm3/g) were all estimated from these data. These properties make this material suitable for use as support in the preparation of high-surface-area solid catalysts. (Reproduced with permission from The American Chemical Society.)...

The thin film of silica-surfactant mesostructured material was prepared by the reactions of TMOS and C18TAC, as reported previously[3]. The film was calcined in air to prepare nanoporous silica films. The adsorption of the dye onto the nanoporous silica film was conducted either by immersing the calcined film into an ethanol solution of the dye or casting the solution onto the film. 

This chapter discusses the fundamental principles for designing nanoporous adsorbents and recent progress in new sorbent materials. For sorbent design, detail discussion is given on both fundamental interaction forces and the effects of pore size and geometry on adsorption. A summary discussion is made on recent progress on the following types of materials as sorbents activated carbon, activated alumina, silica gel, MCM-41, zeolites, n -complexation sorbents, carbon nano tubes, heteropoly compounds, and pillared clays. 2001 Academic Press. 

Carbon dioxide has been used as an alternative probe for characterizing carbonaceous materials (75) and homogeneous polymers (6,9). Carbon dioxide is about the same size as N2, but has a lower vapor pressure, allowing its isotherms to be determined at higher temperatures where the activation energy for diffusion in nanopores is overcome. Specific interactions of COj due to its quadrupole moment appear to play an unimportant role in its adsorption on carbonaceous and mineral surfaces (75 and references therein). In support of this, we have shown that adsorption of Nj and COj on a mesoporous silica gel are of similar magnitude (unpublished results). 

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