scholarly journals The adsorption characteristics and porous structure of bentonite adsorbents, determined from the adsorption isotherms of benzene vapor

2004 ◽  
Vol 69 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Snezana Brezovska ◽  
Biljana Marina ◽  
Biljana Panova ◽  
Donco Burevski ◽  
Vasa Bosevska ◽  
...  
Keyword(s):  
Free Energy ◽  
Porous Structure ◽  
Pore Size ◽  
Adsorption Isotherms ◽  
Micropore Volume ◽  
Benzene Vapor ◽  
Free Energy Of Adsorption ◽  
Volume Filling ◽  
Activated Bentonite ◽  
Characteristic Values

The adsorption of benzene vapor on natural and acid activated bentonites was treated by the theory of volume filling of micropores. The micropore volume and characteristic values of the free energy of adsorptionwere determined from the adsorption isotherms. The Dubinin?Radushkevish?Stoeckli and Dubinin?Astakhov equations were used for this purpose. The results showed that natural bentonite has a more homogeneous micropore structure than the acid activated ones. The characteristic values of the free energy of adsorption for the natural bentonite were higher than those of the acid activated bentonite. This is due to differences in its structure and the pore size.

scholarly journals Adsorption properties and porous structure of sulfuric acid treated bentonites determined by the adsorption isotherms of benzene vapor

2005 ◽  
Vol 70 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Snezana Brezovska ◽  
Biljana Marina ◽  
Donco Burevski ◽  
Biljana Angjuseva ◽  
Vasa Bosevska ◽  
...  
Keyword(s):  
Free Energy ◽  
Sulfuric Acid ◽  
Adsorption Isotherms ◽  
Structural Changes ◽  
Micropore Volume ◽  
Benzene Vapor ◽  
Structural Parameter ◽  
Acid Activation ◽  
Free Energy Of Adsorption ◽  
Differential Distribution

In a previous paper, adsorption isotherms of benzene vapor on natural bentonite from Ginovci, Macedonia, and forms acid activated with 10% and 15% solutions of hydrochloric were interpreted by means of the Dubinin-Radushkevich-Stoeckli and Dubinin-Astakhov equations; the investigation has been continued with bentonites acid activated with 10% and 15% solutions of sulfuric acid where X-ray analysis indicates smaller structural changes. Using the above equations, the heterogeneity of the micropores and the energetic heterogeneity of the bentonites were determined from the differential distribution of the micropore volume with respect to the structural parameter of the equations characterizing the microporous structure and to the molar free energy of adsorption. Activated bentonites obtain bigger pores but also a certain quantity of new small pores appear during acid activation with the higher concentration of acid. The micropore volumes, determined from the adsorption of benzene vapor, of bentonites activated with 10 % and 15 % solution of hydrochloric acid (144.60 cm3 kg-1 and 110.06 cm3 kg-1, respectively), decrease in comparison with that of natural bentonite (162.55 cm3 kg-1). In contrast, the values of the micropore volume for bentonities treated with 10 % and 15 % solutions of sulfuric acids increase (169.19 cm3 kg-1 and 227.74 cm3 kg-1). That is due to the difference in the structural changes occurring during activation with hydrochloric and sulfuric acids. The values of the free energy of adsorption of benzene vapor for natural bentonite are higher than those of the acid activated bentonities, what is in accordance with the structural and porosity changes.

scholarly journals Porous and adsorption properties of hydrated cement paste

2004 ◽  
Vol 58 (1) ◽  
pp. 6-9 ◽  
Author(s):  
Biljana Marina ◽  
Snezana Brezovska ◽  
Donco Burevski ◽  
Biljana Panova
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Adsorption Isotherms ◽  
Favorable Effect ◽  
Hydrated Cement ◽  
Free Energy Of Adsorption ◽  
Characteristic Energy ◽  
Cement Pastes ◽  
Hydrated Cement Paste

Adsorption isotherms of benzene on hydrated cement pastes prepared by cement ground with and without the addition of grinding aids, triethanol amine (TEA) and ethylene glycol (EG) were investigated. The adsorption isotherms were interpreted by means of the Dubinin-Astakhov (DA) and Dubinin-Radushkevich-Stoeckli (DRS) equations. The microporous structure of cement gel (C-S-H) in the cement pastes, and changes in the Gibbs free energy of adsorption were determined. The mechanical properties of the cement pastes were also measured. It was evident that pastes with additives had different parameters of the DRS and DA equations: the volume and dimensions of the gel pores, the distribution of the dimensions, the characteristic energy of adsorption, and the change in the Gibbs free energy of adsorption. The mechanical properties were also different. The dispersity of the additive-containing ground cements had a favorable effect on the hydration processes. When applying TEA, it was also necessary to analyze its influence on the chemical behavior of hydration in the starting period.

A Study of Hydrogen Adsorption in Pretreated Nanocarbon

2002 ◽  
Vol 740 ◽  
Author(s):  
Sang Moon Lee ◽  
Satoshi Ohshima ◽  
Kunio Uchida ◽  
Motoo Yumura
Keyword(s):  
Thermal Treatment ◽  
Porous Structure ◽  
Surface Area ◽  
Adsorption Isotherms ◽  
Hydrogen Adsorption ◽  
Total Surface Area ◽  
Micropore Volume

ABSTRACTA thermal treatment was applied with CO2 and air for the development of a porous structure. Adsorption isotherms of nitrogen were measured on well-characterized Ni-C nanoparticles. The thermal treatment with CO2 increased the total surface area and micropore volume. In addition, the thermal treatment with CO2 increased the hydrogen adsorption.

Porous Structure and Transport Properties of a Carbonized Phenolic Resin

1995 ◽  
Vol 60 (2) ◽  
pp. 172-187 ◽  
Author(s):  
Pavel Fott ◽  
František Kolář ◽  
Zuzana Weishauptová
Keyword(s):  
Porous Structure ◽  
Transport Properties ◽  
Phenolic Resin ◽  
Arrhenius Equation ◽  
Mercury Porosimetry ◽  
Micropore Volume ◽  
Microporous Structure ◽  
Wetting And Drying ◽  
Phenolic Resins ◽  
Kinetics Of

On carbonizing phenolic resins, the development of porous structure takes place which influences the transport properties of carbonized materials. To give a true picture of this effect, specimens in the shape of plates were prepared and carbonized at various temperatures. The carbonizates obtained were studied by adsorption methods, electron microscopy, and mercury porosimetry. Diffusivities were evaluated in terms of measuring the kinetics of wetting and drying. It was found out that the porous structure of specimens in different stages of carbonization is formed mostly by micropores whose volumes were within 0.06 to 0.22 cm3/g. The maximum micropore volume is reached at the temperature of 750 °C. The dependence of diffusivity on the carbonization temperature is nearly constant at first, begins to increase in the vicinity of 400 °C, and at 600 °C attains its maximum. The experimental results reached are in agreement with the conception of the development and gradual closing of the microporous structure in the course of carbonization. The dependence of diffusivity on temperature can be expressed by the Arrhenius equation. In this connection, two possible models of mass transport were discussed.

scholarly journals Computer Analysis of the Porous Structure of Activated Carbons Derived from Various Biomass Materials by Chemical Activation

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4121
Author(s):  
Mirosław Kwiatkowski ◽  
Elżbieta Broniek
Keyword(s):  
Porous Structure ◽  
Adsorption Isotherms ◽  
Computer Analysis ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Adsorbed Layer ◽  
Dry Mass ◽  
Mass Ratio ◽  
Adsorption Volume ◽  
Homogeneous Surface

In this study, the preparation of activated carbons from various materials of biomass origin by activation with potassium hydroxide and a comprehensive computer analysis of their porous structure and adsorption properties based on benzene (C6H6) adsorption isotherms were carried out. In particular, the influence of the mass ratio of the activator’s dry mass to the char mass on the formation of the microporous structure of the obtained activated carbons was analysed. The summary of the analyses carried out based on benzene adsorption isotherms begged the conclusion that activated carbon with a maximum adsorption volume in the first adsorbed layer and homogeneous surface can be obtained from ebony wood at a mass ratio of the activator to the char of R = 3. The obtained results confirmed the superiority of the new numerical-clustering-based adsorption analysis (LBET) method over simple methods of porous structure analysis, such as the Brunauer–Emmett–Teller (BET) and Dubinin–Raduskevich (DR) methods. The LBET method is particularly useful in the evaluation of the influence of the methods and conditions of production of activated carbons on the formation of their porous structure. This method, together with an appropriate economic analysis, can help in the precise selection of methods and conditions for the process of obtaining activated carbons at specific manufacturing costs, and thus makes it possible to obtain materials that can successfully compete with those of other technologies used in industrial practice and everyday life.

Electrochemical Measurement of the Free Energy of Adsorption ofn-Alkanethiolates at Ag(111)

1998 ◽  
Vol 120 (5) ◽  
pp. 1062-1069 ◽  
Author(s):  
David W. Hatchett ◽  
Rory H. Uibel ◽  
Keith J. Stevenson ◽  
Joel M. Harris ◽  
Henry S. White
Keyword(s):  
Free Energy ◽  
Electrochemical Measurement ◽  
Free Energy Of Adsorption

Standard Free Energy of Adsorption at Liquid Interfaces

1991 ◽  
pp. 277-292 ◽  
Author(s):  
D. K. Chattoraj ◽  
L. N. Ghosh ◽  
P. K. Mahapatra
Keyword(s):  
Free Energy ◽  
Standard Free Energy ◽  
Liquid Interfaces ◽  
Free Energy Of Adsorption

scholarly journals The Influence of Loop Heat Pipe Evaporator Porous Structure Parameters and Charge on Its Effectiveness for Ethanol and Water as Working Fluids

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7029
Author(s):  
Krzysztof Blauciak ◽  
Pawel Szymanski ◽  
Dariusz Mikielewicz
Keyword(s):  
Porous Structure ◽  
Pore Size ◽  
Heat Pipe ◽  
Capillary Pressure ◽  
Pressure Difference ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Working Fluids ◽  
Integral Characteristics ◽  
Sintered Stainless Steel

This paper presents the results of experiments carried out on a specially designed experimental rig designed for the study of capillary pressure generated in the Loop Heat Pipe (LHP) evaporator. The commercially available porous structure made of sintered stainless steel constitutes the wick. Three different geometries of the porous wicks were tested, featuring the pore radius of 1, 3 and 7 µm. Ethanol and water as two different working fluids were tested at three different evaporator temperatures and three different installation charges. The paper firstly presents distributions of generated pressure in the LHP, indicating that the capillary pressure difference is generated in the porous structure. When installing with a wick that has a pore size of 1 μm and water as a working fluid, the pressure difference can reach up to 2.5 kPa at the installation charge of 65 mL. When installing with a wick that has a pore size of 1 μm and ethanol as a working fluid, the pressure difference can reach up to 2.1 kPa at the installation charge of 65 mL. The integral characteristics of the LHP were developed, namely, the mass flow rate vs. applied heat flux for both fluids. The results show that water offers larger pressure differences for developing the capillary pressure effect in the installation in comparison to ethanol. Additionally, this research presents the feasibility of manufacturing inexpensive LHPs with filter medium as a wick material and its influence on the LHP’s thermal performance.

Sign in / Sign up

Export Citation Format

Share Document