Adsorption titania

Kurrat R, Prenosil J E and Ramsden J J 1997 Kinetios of human and bovine serum albumin adsorption at silioa-titania surfaoes J. Colloid Interface Sol. 185 1-8... 

For other adsorptives the experimental evidence, though less plentiful than with nitrogen, supports the view that at a given temperature the lower closure point is never situated below a critical relative pressure which is characteristic of the adsorptive. Thus, for benzene at 298 K Dubinin noted a value of 017 on active carbons, and on active charcoals Everett and Whitton found 0-19 other values, at 298 K, are 0-20 on alumina xerogel, 0-20-0-22 on titania xerogel and 017-0-20 on ammonium silicomolybdate. Carbon tetrachloride at 298 K gives indication of a minimum closure point at 0-20-0-25 on a number of solids including... 

Fig. 4.15 a,-plots for the adsorption of nitrogen on a sample of microporous titania, before and after nonane treatment. Curve (A), before nonane pre-adsorption curves (B), (C), (D) after nonane pre-adsorption, followed by outgassing at (B) 250° (C) 150°C (D) 25°C. The a,-plots were based on standard nitrogen isotherms having the same c-values as the isotherms of... 

A detailed study of the physical and chemical adsorption of water on three xerogels, ferric oxide, alumina and titania, as well as on silica (cf. p. 272) has been carried out by Morimoto and his co-workers. Each sample was outgassed at 600°C for 4 hours, the water isotherm determined at or near 20°C, and a repeat isotherm measured after an outgassing at 30 C. The procedure was repeated on the same sample after it had been evacuated at a... 

In our experiment, photocatalytic decomposition of ethylene was utilized to probe the surface defect. Photocatalytic properties of all titania samples are shown in table 2. From these results, conversions of ethylene at 5 min and 3 hr were apparently constant (not different in order) due to the equilibrium between the adsorption of gaseous (i.e. ethylene and/or O2) on the titania surface and the consumption of surface species. Moreover it can be concluded that photoactivity of titania increased with increasing of Ti site present in titania surface. It was found that surface area of titania did not control photoactivity of TiOa, but it was the surface defect in titania surface. Although, the lattice oxygen ions are active site of this photocatalytic reaction since it is the site for trapping holes [4], this work showed that the presence of oxygen vacancy site (Ti site) on surface titania can enhance activity of photocatdyst, too. It revealed that oxygen vacancy can increase the life time of separated electron-hole pairs. 

Li, Y. and Kim, S.J. (2005) Synthesis and characterization of nano titania particles embedded in mesoporous silica with both high photocatalytic activity and adsorption capability. Journal of Physical Chemistry B, 109, 12309-12315. 

Topogildis, E., Cass, C.J., Cass, A.E.G. and Durrant, J.R. (2001) Factors that affect protein adsorption on nanostructured titania films A novel spectrochemical application to sensing. Langmuir, 17, 7899—7906. 

Morales F., de Smit E., de Groot F.M.F., Visser T., and Weckhuysen B.M. 2007. Effects of manganese oxide promoter on the CO and H2 adsorption properties of titania-supported cobalt Fischer-Tropsch catalysts. J. Catal. 246 91-99. 

At the end of the seventies, scientists at Exxon discovered that metal particles supported on titania, alumina, ceria and a range of other oxides, lose their ability to chemisorb gases such as H2 or CO after reduction at temperatures of about 500 °C. Electron microscopy revealed that the decreased adsorption capacity was not caused by particle sintering. Oxidation, followed by reduction at moderate temperatures restored the adsorption properties of the metal in full. The suppression of adsorption after high temperature reduction was attributed to a strong metal-support interaction, abbreviated as SMSI [2]. 

In conclusion, nanorods are a potentially interesting material, but present results still do not allow understanding of whether the nanostructure leads to an improvement of the intrinsic photocatalytic behaviour, or whether other factors (accessible surface area, enhanced adsorption, etc) are responsible for the observed differences. In ZnO nanorods have been shown quite recently by surface photovoltage spectroscopy that the built-in electrical field is the main driving force for the separation of the photogenerated electron-hole pairs.191 This indicates that the nano-order influences the photophysical surface processes after photogeneration of the electron-hole pairs. A similar effect could be expected for Titania nanorods. However, present data do not support this suggestion, mainly due to the absence of adequate photo-physical and -chemical characterization of the materials and surface processes. 

The present paper focuses on the interactions between iron and titania for samples prepared via the thermal decomposition of iron pentacarbonyl. (The results of ammonia synthesis studies over these samples have been reported elsewhere (4).) Since it has been reported that standard impregnation techniques cannot be used to prepare highly dispersed iron on titania (4), the use of iron carbonyl decomposition provides a potentially important catalyst preparation route. Studies of the decomposition process as a function of temperature are pertinent to the genesis of such Fe/Ti02 catalysts. For example, these studies are necessary to determine the state and dispersion of iron after the various activation or pretreatment steps. Moreover, such studies are required to understand the catalytic and adsorptive properties of these materials after partial decomposition, complete decarbonylation or hydrogen reduction. In short, Mossbauer spectroscopy was used in this study to monitor the state of iron in catalysts prepared by the decomposition of iron carbonyl. Complementary information about the amount of carbon monoxide associated with iron was provided by volumetric measurements. 

The application of the SEA approach to other systems is straightforward, and involves the three steps (PZC determination, uptake-pH survey, and tuned reduction) demonstrated in the earlier sections. It has recently been suggested that electrostatic adsorption over silanol groups is the cause for metal overexchange in low-aluminum zeohtes [61], It is presently being employed to study noble metal uptake on pure oxides of titania, ceria, zirconia, and niobia. 

Role of adsorption in photocatalyzed reactions of organic molecules in aqueous titania suspensions, Langmuir 8 (1992) 481. 

Liu etal. [32] reported the characteristics and reactivity of highly ordered mesoporous carbon-titania hybrid materials synthesized via organic-inorganic-amphiphilic coassembly followed by in situ crystallization. In the degradation of Rhodamine B these materials also show enhanced properties due to the dispersion/stabilization of small titania nanocrystals and the adsorptive capacity of the nanocarbon. 

Kraemer, S.M. Hering, J.G. (1997) Influence of solution saturation state on the kinetics of ligand-controlled dissolution of oxide phases. Geochim. Cosmochim. Acta 61 2855-2866 Kraemer, S.M., Xu, J., Raymond, K.N. Spo-sito, G. (2002) Adsorption of Pb(II) and Eu(III) by oxide minerals in the presence of natural and synthetic hydroxamate sidero-phores. Environ. Sd. Technol. 36 1287-1291 Kraemer, S.M. Cheah, S.-F. Zapf, R. Xu, J. Raymond, KN. Sposito, G. (1999) Effect of hydroxamate siderophores on Fe release and Pb(II) adsorption by goefhite. Geochim. Cosmochim. Acta 63 3003—3008 Kratohvil, S. Matijevic, E. (1987) Preparation and properties of coated uniform colloidal partides. I. Aluminum (hydrous) oxide on hematite, diromia, and titania. Adv Ceram. Mater. 2 798-803... 

Different from the formation mechanism of titania nanotubes, Fe203 nanotubes are formed by a coordination-assisted dissolution process [95]. The presence of phosphate ions is the crucial factor that induces the formation of a tubular structure, which results from the selective adsorption of phosphate ions on the surfaces of hematite particles and their ability to coordinate with ferric ions. 

Adsorption isotherms for AMP-QS onto kaolin, titania and calcium carbonate are shown in Figure 4. Viscosity profiles obtained when AMP is used to disperse titania and kaolin are shown in Figures 5-7. 

Figure 4 Adsorption isotherms for AMP-95 onto kaolin, titania and calcium carbonate...

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