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 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.

Inhibition of corrosion of copper in acids by norfloxacin

2017 ◽  
Vol 64 (1) ◽  
pp. 92-102 ◽  
Author(s):  
Thanapackiam P. ◽  
Kumaravel Mallaiya ◽  
Rameshkumar S. ◽  
Subramanian S.S.
Keyword(s):  
Free Energy ◽  
Sulfuric Acid ◽  
Nitric Acid ◽  
Metal Surface ◽  
Inhibition Efficiency ◽  
Acid Solutions ◽  
Free Energy Of Adsorption ◽  
Acid Media ◽  
Content Type ◽  
Sulfuric Acid Solutions

Purpose This paper aims to evaluate the inhibition efficiency of norfloxacin on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. Design/methodology/approach Evaluation was carried out by electrochemical techniques such as electrochemical impedance spectroscopy and potentiodynamic polarization studies. Scanning electron microscopy was used, and it finally confirmed the existence of the adsorbed film. Findings The electrochemical measurements showed that norfloxacin has good inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The inhibition action of norfloxacin in both of the corrosive media was observed to be of mixed type but with more of cathodic nature. The temperature dependence of the corrosion rate was studied in the temperature range from 35 to 55°C and the activation energy (Ea) was calculated. The adsorption of norfloxacin molecules on copper surface obeyed Langmuir adsorption isotherm. Studies on the potential of zero charge have been carried out to establish the mechanism of adsorption of the inhibitor onto the metal surface. The thermodynamic parameters such as the adsorption equilibrium constant (Kads) and the free energy of adsorption (ΔGads) were calculated. The value of free energy of adsorption very close to −40 kJmol−1 indicates that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in value of Ea with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface. Originality/value This paper indicates that norfloxacin can act as a good inhibitor for the corrosion of copper in both the acid media.

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.

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

scholarly journals Effect of Structure and Chemical Activation on the Adsorption Properties of Green Clay Minerals for the Removal of Cationic Dye

2018 ◽  
Vol 8 (11) ◽  
pp. 2302 ◽  
Author(s):  
Abdelfattah Amari ◽  
Hatem Gannouni ◽  
Mohammad Khan ◽  
Mohammed Almesfer ◽  
Abubakr Elkhaleefa ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Pore Volume ◽  
Acid Treatment ◽  
Structural Changes ◽  
Chemical Activation ◽  
Total Pore Volume ◽  
Batch Adsorption ◽  
Acid Activation ◽  
Cationic Dye ◽  
Average Pore

In this study, natural clay minerals with green appearance were treated with sulfuric acid. Mass percentage of acid (wt%), temperature (T), contact time (t) and liquid-to-solid mass ratio (R) are used as the prevailing factors that determine the extent of acid-activation. The values of these factors range from 15–50%, 60–90 °C, 1.5–6 h and 4–7, respectively. The study has focused on the structural changes as well as textural characteristics of the clay. Three activated clay samples were prepared under different treatment conditions. The samples were characterized using X-ray powder diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscope (SEM), chemical analysis and N2 adsorption techniques. Characterization of the treated clay minerals exhibited significant structural changes to a greater extent of acid-activation, from being partially crystalline to being amorphous silica. The surface area and total pore volume of clay increased proportionally with the level of acid treatment. The average pore diameter behaved differently. During the strong acid treatment, a large increase in pore volume and the enlargement of the pore size distribution were observed. This suggests that considerable structural changes and partial destruction may have occurred in this condition. The removal of methylene blue, used as cationic dye, from aqueous solution by the batch adsorption technique on three prepared acid-activated clay samples was studied. The Langmuir model was found to agree well with the experimental data.

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 FREE ENERGY OF AQUEOUS SULFURIC ACID

1924 ◽  
Vol 46 (1) ◽  
pp. 75-83 ◽  
Author(s):  
David F. Smith ◽  
Joseph E. Mayer
Keyword(s):  
Free Energy ◽  
Sulfuric Acid ◽  
Aqueous Sulfuric Acid

scholarly journals Adsorption Equilibrium of 1, 1-Dichloro-1-fluoroethane (HCFC-141b) on a Hydrophobic Zeolite

1998 ◽  
Vol 16 (2) ◽  
pp. 67-75 ◽  
Author(s):  
Wen-Tien Tsai ◽  
Ching-Yuan Chang ◽  
Chih-Yin Ho
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Adsorption Isotherms ◽  
Ozone Depletion ◽  
Adsorption Equilibrium ◽  
Stratospheric Ozone ◽  
Stratospheric Ozone Depletion ◽  
Equilibrium Isotherms ◽  
Entropy Of Adsorption

Of the major replacements for chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) are now accepted as being prime contributors to stratospheric ozone depletion. As a consequence, the development of adsorbents capable of adsorbing and recovering specific HCFCs has received great attention. This paper describes an investigation of the adsorption equilibrium of 1, 1-dichloro-1-fluoroethane (HCFC-141b) vapour on a commercial hydrophobic zeolite. The corresponding Henry, Freundlich and Dubinin–Radushkevich (D–R) equilibrium isotherms have been determined and found to correlate well with the experimental data. Based on the Henry adsorption isotherms obtained at 283, 303 and 313 K. thermodynamic properties such as the enthalpy, free energy and entropy of adsorption have been computed for the adsorption of HCFC-141b vapour on the adsorbent. The results obtained could be useful in the application of HCFC adsorption on the hydrophobic zeolite studied.

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