Application of quasi-isothermal thermogravimetry for estimation of some properties of hydration layers in mesoporous adsorbents

Colloids and Interfaces

Kucio

Sydorchuk³

et al. 2018

The formation of hierarchical, multimodal porosity materials with controlled shape and size of pores is the essential challenge in materials science. Properties of silica materials depend largely on different features: crystal structure, dispersity, surface composition, and porosity as well as the method of preparation and possible modification. In this paper, multimodal silicas obtained using different additives are presented. A-50 and A-380 aerosils and wide-porous SiO 2 milled at 300 rpm were used as the additives in the sol stage at 20 • C, the sol-gel stage followed by hydrothermal modification (HTT) at 200 • C, or in the mechanochemical treatment (MChT) process. The characterizations were made by application of N 2 adsorption/desorption, SEM imaging, quasi-isothermal thermogravimetry (Q-TG), dynamic thermogravimetry/derivative thermogravimetry/differential thermal analysis (TG/DTG/DTA), and cryoporometry differential scanning calorimetry (DSC) methods. Results showed that such a one-step preparation method is convenient and makes it possible to obtain multimodal silicas of differentiated porous structures and surface chemistry.

Section: Quasi-isothermal Desorption Of Watermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of Multimodal Silicas Using TG/DTG/DTA, Q-TG, and DSC Methods

Colloids and Interfaces

Kucio

Sydorchuk³

et al. 2018

“…These data were used as initial ones for calculation of energetic characteristics of the tested samples. This method was described precisely in [30, 31]. On the basis of the obtained data, total concentrations of water adsorbed on the surface of studied adsorbents (mg/g) were calculated.…”

Section: Methodsmentioning

confidence: 99%

Complex investigations of structural and thermal properties of silica-titania adsorbents

Skubiszewska–Zięba

Лебода

et al. 2011

J Therm Anal Calorim

Self Cite

Mesoporous titanium-containing silicas with different Titania contents were investigated. The structural parameters of the materials were characterized by low-temperature adsorption/desorption of nitrogen and X-ray diffraction analysis. The thermodesorption of water using the quasi-isothermal thermogravimetry as well as the differential scanning calorimetry were used to characterize thermal and surface properties of these materials. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent/water interfaces were calculated. It was stated that the increase of Titania content causes a gradual decrease of specific surface area and formation of biporous structure inside the tested materials. The water thermodesorption from the surface proceeds in two or three stages, which is connected mainly with pore distribution and TiO2 content. One can observe the increase of the total surface free energy (ΔGΣ) with the increasing TiO2 content, but the largest ΔGΣ value at the adsorbent/strongly bound water interface is exhibited by the adsorbent of intermediate content (30%) of TiO2. Freezing temperature of water contained in the pores of the studied materials is connected largely with their porous structure. Due to the well developed porous structure, the water freezing process is a multi-stage one.

“…These data were used as initial ones for calculation of energetic characteristics of the tested samples. This method was described precisely in [28]. On the basis of the obtained data, total concentrations of water adsorbed on the surface of studied adsorbents (mg/g) were calculated.…”

Section: Quasi-isothermal Desorption Of Watermentioning

confidence: 99%

Structural, thermal and energetic characteristics of synthetic active carbons prepared on the basis of ion-exchange resin Amberlite IRC 84

Kucio

Skubiszewska–Zięba

et al. 2018

J Therm Anal Calorim

A series of activated carbons was prepared from the ion-exchange resin (Amberlite IRC-84, Rohm and Haas) differing in Ca 2? content and studied by means of adsorption (N 2 adsorption) and thermogravimetric methods. Thermogravimetry was performed in two ways: classical and quasi-isothermal. Preparation processes proceeded in different conditions (temperature and atmosphere). This resulted in changes of their porosity and thermal stability. As shown by the studies, low temperature and calcium ion content are not suitable for obtaining carbon materials with desirable structural properties and good thermal resistance. Ca 2? ions increase makes it possible to obtain carbonaceous materials with a large specific surface area, well-developed porosity and high thermal stability. The quasi-isothermal thermogravimetric analysis allowed to characterize energetic and structural heterogeneity of active carbons. Changes in the free energies of adsorbed water layer during their desorption as well as dependence of the effective radius of a drop evaporated from the surface on the adsorbed water concentration were determined. The dependence dG=dM H 2 O C H 2 O ð Þ was examined under the conditions of low coverage of carbon surfaces with the adsorbed water which may indicate formation of various types of water clusters on the surfaces.