BET Adsorption Isotherm and Surface Heterogeneity

1992 ◽  
Vol 57 (6) ◽  
pp. 1201-1209
Author(s):  
Lydia Ethel Cascarini de Torre ◽  
Eduardo Jorge Bottani
Keyword(s):  
Distribution Function ◽  
Adsorption Isotherm ◽  
Statistical Mechanics ◽  
Adsorption Isotherms ◽  
Surface Heterogeneity ◽  
Adsorption Energies ◽  
Multilayer Formation ◽  
Effect Of Surface

The BET adsorption isotherm is modified in order to take account of surface heterogeneity. The adsorption isotherm is obtained following the statistical mechanics formalism, proposed by Steele, and the effect of surface heterogeneity is limited to the first layer. A Gaussian adsorption energies distribution function is used to describe surface heterogeneity. The variations of the C parameter, multilayer formation and the inversion of adsorption isotherms are analysed.

INFLUENCE OF GEOMETRIC AND ENERGETIC HETEROGENEITY ON ADSORPTION ISOTHERMS

Fractals ◽  
1995 ◽  
Vol 03 (02) ◽  
pp. 235-250 ◽  
Author(s):  
MASSIMILIANO GIONA ◽  
MANUELA GIUSTINIANI ◽  
DOUGLAS K. LUDLOW
Keyword(s):  
Experimental Data ◽  
Simple Model ◽  
Adsorption Isotherms ◽  
Energy Landscape ◽  
Adsorption Equilibria ◽  
Preferential Adsorption ◽  
Consistent Model ◽  
Energetic Heterogeneity ◽  
Adsorption Energies ◽  
Effect Of Surface

The relationships between geometric roughness and energetic heterogeneity are discussed by considering a thermodynamically consistent model of adsorption isotherms (Keller model) which encompasses fractal scaling and the dependence of the adsorption energies on the coverage. Experimental results validate this model and indicate that it can be used not only to interpolate experimental data but also to predict adsorption equilibria of multicomponent rnixtures. The peculiar non-Henry behaviour of the Keller model at low pressure is discussed by considering a simple model of preferential adsorption on a rough energy landscape and including the effect of surface diffusion.

scholarly journals Argon and Nitrogen Physical Adsorption on Boron Nitride

1987 ◽  
Vol 4 (1-2) ◽  
pp. 121-130 ◽  
Author(s):  
E.J. Bottani ◽  
J.R. Zarate ◽  
L.E. Torre Cascarini De
Keyword(s):  
Phase Transition ◽  
Distribution Function ◽  
Boron Nitride ◽  
Adsorption Isotherms ◽  
Physical Adsorption ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Adsorbed Phase ◽  
Isotherm Adsorption ◽  
Adsorption Energies

Physical adsorption isotherms of N2 and Ar on boron nitride are analysed and the behaviour of the adsorbed phase is discussed. Different models are used to interpret the adsorbed states. The behaviour of the BET C parameter suggests that a phase-transition occurs in Ar adsorption which is not showed in its isotherm. Adsorption energies distribution functins are calculated using a double Gaussian as distribution function. Nitrogen cross-sectional areas, under experimental conditions are estimated respect to those of the Ar.

scholarly journals Filter properties of seam material from paved urban soils

2008 ◽  
Vol 12 (2) ◽  
pp. 691-702 ◽  
Author(s):  
T. Nehls ◽  
G. Jozefaciuk ◽  
Z. Sokolowska ◽  
M. Hajnos ◽  
G. Wessolek
Keyword(s):  
Adsorption Isotherms ◽  
Urban Form ◽  
Urban Soils ◽  
Water Vapor Adsorption ◽  
Filling Material ◽  
High Adsorption ◽  
Adsorption Energies ◽  
The Impact ◽  
Original Construction

Abstract. Depositions of all kinds of urban dirt and dust including anthropogenic organic substances like soot change the filter properties of the seam filling material of pervious pavements and lead to the formation of a new soil substrate called seam material. In this study, the impact of the particular urban form of organic matter (OM) on the seam materials CECpot, the specific surface area (As), the surface charge density (SCD), the adsorption energies (Ea) and the adsorption of Cd and Pb were assessed. The Cd and Pb displacement through the pavement system has been simulated in order to assess the risk of soil and groundwater contamination from infiltration of rainwater in paved urban soils. As, Ea and SCD derived from water vapor adsorption isotherms, CECpot, Pb and Cd adsorption isotherms where analyzed from adsorption experiments. The seam material is characterized by a darker munsell-color and a higher Corg (12 to 48g kg-1) compared to the original seam filling. Although, the increased Corg leads to higher As (16m2g-1) and higher CECpot (0.7 to 4.8cmolckg-1), with 78cmolckg-1C its specific CECpot is low compared to OM of non-urban soils. This can be explained by a low SCD of 1.2×10-6molc m-2 and a low fraction of high adsorption energy sites which is likely caused by the non-polar character of the accumulated urban OM in the seam material. The seam material shows stronger sorption of Pb and Cd compared to the original construction sand. The retardation capacity of seam material for Pb is similar, for Cd it is much smaller compared to natural sandy soils with similar Corg concentrations. The simulated long term displacement scenarios for a street in Berlin do not indicate an acute contamination risk for Pb . For Cd the infiltration from puddles can lead to a breakthrough of Cd through the pavement system during only one decade. Although they contain contaminations itself, the accumulated forms of urban OM lead to improved filter properties of the seam material and may retard contaminations more effectively than the originally used construction sand.

scholarly journals Carbon Dioxide Capture in Homogeneous and Heterogeneous Surfaces of Porous Silica Glass

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1260
Author(s):  
Chontira Boonfung ◽  
Chaiyot Tangsathitkulchai ◽  
Atichat Wongkoblap
Keyword(s):  
Carbon Dioxide ◽  
Functional Groups ◽  
Adsorption Isotherms ◽  
Silica Glass ◽  
Surface Defects ◽  
Porous Silica ◽  
Surface Heterogeneity ◽  
Slit Pore ◽  
Porous Silica Glass ◽  
Carbon Dioxide Co2

Experimental and simulation studies for carbon dioxide (CO2) adsorption on porous silica glass were performed to reveal how surface heterogeneity can affect the adsorption mechanism of CO2. In performing the simulation, the structure of porous silica glass was modeled as a slit pore consisting of parallel walls of connected SiO4 units. The adsorption isotherms of CO2 at 283 K were generated for a series of pore widths using a Monte Carlo ensemble. The defective surfaces created by random removal of surface atoms and the surfaces containing hydroxyl functional groups were chosen to represent the surface heterogeneity for the simulation tasks. The isotherms derived for the defective surfaces showed a rapid adsorption at low pressures because of the stronger interaction between the rough nonuniform surfaces and CO2 molecules. For the role of surface functional groups, the adsorption isotherms dramatically increased with an increasing number of functional groups. The amount of CO2 adsorbed for randomly placed functional groups was greater than that for the presence of functional groups at the pore edges. The proper control of surface heterogeneity by manipulating both the amounts of hydroxyl surface groups and surface defects should help enhance the efficient capture of CO2 in porous silica glass.

scholarly journals A Statistical Approach to Determine Optimal Models for IUPAC-Classified Adsorption Isotherms

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4565 ◽  
Author(s):  
Rahman ◽  
Muttakin ◽  
Pal ◽  
Shafiullah ◽  
Saha
Keyword(s):  
Adsorption Isotherm ◽  
Adsorption Isotherms ◽  
Fossil Fuels ◽  
Information Criterion ◽  
Single Type ◽  
Average Error ◽  
Type I ◽  
Bootstrap Sampling ◽  
Selection Probability ◽  
Type Iv

Adsorption heat transformation (AHT) systems can play a major role in protecting our environment by decreasing the usage of fossil fuels and utilizing natural and alternative working fluids. The adsorption isotherm is the most important feature in characterizing an AHT system. There are eight types of International Union of Pure and Applied Chemistry (IUPAC) classified adsorption isotherms for different “adsorbent-adsorbate” pairs with numerous empirical or semi-empirical mathematical models to fit them. Researchers face difficulties in choosing the best isotherm model to describe their experimental findings as there are several models for a single type of adsorption isotherm. This study presents the optimal models for all eight types of isotherms employing several useful statistical approaches such as average error; confidence interval (CI), information criterion (ICs), and proportion tests using bootstrap sampling. Isotherm data of 13 working pairs (which include all eight types of IUPAC isotherms) for AHT applications are extracted from literature and fitted with appropriate models using two error functions. It was found that modified Brunauer–Emmet–Teller (BET) for Type-I(a) and Type-II; Tóth for Type-I(b); GAB for Type-III; Ng et al. model for Type-IV(a) and Type-IV(b); Sun and Chakraborty model for Type-V; and Yahia et al. model for Type-VI are the most appropriate as they ensure less information loss compared to other models. Moreover; the findings are affirmed using selection probability; overall; and pairwise proportion tests. The present findings are important in the rigorous analysis of isotherm data.

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