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Abstract  

Thermogravimetric analysis of silica gel has shown that the loss in weight between 30° and 910°C can be quantitatively explained on the basis of water being lost from three distinct and different populations of sites on the silica gel surface. The results indicate that the site energies of the three different populations are randomly distributed and, consequently, the resulting weight loss steps from each population can be described by the integral of a simple normal distribution with temperature. The calculated weight loss obtained by assuming three different site-groups having randomly distributed adsorption energies is, within experimental error, coincident with the experimental data. It is also shown that the water evolved from the second population of sites originates from strongly bound water and may also contain water generated by the condensation of (geminal) silanol groups contained in the overlapping and neighbouring population.

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Abstract  

This article presents results of the experimental investigation on the adsorption of the water vapor on silica gel. Two independent experimental methods has been used, viz. the constant-volume-variable-pressure (CVVP) system and variable pressure thermogravimetry (TG). Results from these two methods are compared with each other. Also the isosteric heat of adsorption of this system has been determined from the equilibrium data. The silica gels investigated here are Fuji Davison type 'A' and type 'RD'. Adsorption isotherm of water vapor have been measured under a variety of conditions all referring to chiller operation cycles, i.e. temperatures from 303 to 358 K and pressures from 500 to 7000 Pa. The data collected from the two independent experiments compare very favorably with each other and their trends are consistent with those of the adsorption chiller manufacturer. This lends significant weight to our experimental data on silica gel+water systems as being valuable to the adsorption chiller manufacturers and the scientific community.

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and adsorptive, shape and size of pores, etc. Aristov et al. [ 8 ] obtained sorption behavior of water vapor on Fuji RD silica gels which have 820 m 2 g −1 BET surface areas and particle size between 0.3 and 1.0 mm using CAHN 2000 thermo

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Abstract  

The Q-TG mass loss and first derivative Q-DTG mass loss accompanying benzene thermodesorption from silica gel samples under quasi-isothermal conditions were studied with a Derivatograph Q-1500 D (MOM, Hungary). The isotherms of adsorption-desorption of benzene vapour on different porous silica gels were measured gravimetrically by using a McBain balance. The benzene mass loss in the adsorption region, obtained from the Q-TG curves, and the adsorption capacity, established gravimetrically, exhibited a satisfactory correlation.

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Summary

The new obtained sorbent based on silica gel modified with polyaniline was used as a stationary phase in the ion chromatography of anions. NO3- and NO2- ions were analyzed by UV spectrophotometric detection (200 nm). It can be stated that the optimal mobile phase was a 0.05 M hydrochloric acid and the optimal flow speed was 0.3 mL min−1. The separation of both anions in the presented condition was satisfactory. The resolution factor (peak resolution) was 3.3. It suggests the possibility of the column application for simultaneous speciation analysis of nitrate ions.

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quality of diesel fuel and other fuel mixtures [ 1 ]. Silica gel is a solid formed by silicon dioxide, SiO 2 . It may contain admixtures of different inorganic and organic substances. Due to the presence of Si–OH groups (silanols), surface of non

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experimental measurement of the heat capacity of a complex system which consists of two components of comparable weight fractions, namely, a silica gel KSK and calcium chloride confined to its pores [ 1 ]. The main motivation was to obtain for this composite

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silica gel so that a very slow reaction occurs with the formation of a sparingly soluble compound. When the concentration of this compound exceeds the solubility limits, crystals will be formed, while the main function of the gel is to control the flow of

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Abstract  

The use of ionizing radiation to achieve some desired effect on silica gel, applicable to the adsorption of radionuclides has been investigated as a function of the dose-rate over a wide range of doses, in experiments with strongly alkaline aqueous solutions containing an excess of UO 2 2+ relative to trace concentrations of88Y,103Ru,134Cs and141Ce. The results obtained revealed that γ-irradiation of silica gel was reproduced with an uptake comparable to that measured for the unirradiated-silica gel. Radiation resistance is strongly influenced by the basic macromolecular structure, the presence of water, and the particular environmental exposure conditions.

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Abstract  

Microcrystalline zirconium phosphate (-ZrP), hydrous manganese dioxide (HMnO), ammonium molybdophosphate (AMP) and silica gel supported forms of these materials as well as silica gel (SG) itself were investigated by thermoanalytical, electron microscopic, X-ray diffraction and infrared spectrometric methods. Chemical composition, structure and some related properties of the inorganic ion exchangers mentioned above are reported.

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