Brunauer-Emmett-Teller sorption

Hall et al. (2001) measured the biosorption of copper by P. syringae, fitting the experimental data to the Freundlich, Brunauer-Emmett-Teller (BET), and Langmuir equations. Meaningful maximum sorption capacities... 

Many models have been developed that deal with the sorption properties of wood in the presence of moisture these have been discussed in a number of works (e.g. Skaar, 1972 Siau, 1984). They can be approximately divided into sorption models, such as the Brunauer-Emmett-Teller (BET) model, or solution models (such as the Hailwood-Horrobin, H-H, model). The sigmoidal shapes of sorption or desorption isotherms can be deconvoluted into two components. These are often taken to represent a monomolecular water layer (associated with the primary sorption sites, OH groups), and a multilayer component where the cell wall bound water molecules are less intimately associated with the fixed cell wall OH groups. 

Popper and Bariska (1972) studied the moisture sorption properties of wood chemically modified with acetic (or phthalic) anhydride and analysed the results using Brunauer-Emmett-Teller (BET) theory and the H-H model. Acetylation was found to reduce the number of sorption sites, whereas little effect was noted with phthaloylation. By dividing the sorption isotherm into a monolayer component and a multilayer component using the H-H model, it was shown that there was a large reduction in the... 

Equilibrium sorption of water (solubility) is described by the different isotherms of the Brunauer-Emmett-Teller classification. 

The characteristic inflection in Type II behavior occurs when multilayer sorption starts. The Brunauer, Emmett, Teller (BET) equation, shown as Eq. (4), can describe isotherms where multilayer sorption is evident ... 

Sorption isotherms of model systems were determined gravimetrically and data were modeled using the Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-deBoer (GAB) models. 

The Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-deBoer (GAB) sorption isotherm models were used to obtain experimental steady-state moisture contents in dry basis by linear regression analysis according to Kouassi and Roos (2002). These equations provide the value of monolayer water content, which is an important parameter in food deterioration studies. 

The use of the Brunauer-Emmett-Teller (BET) sorption model by TMT is problematic due to the faet that the BET is fit to sorption data at 30°C and does not consider the temperature dependence of sorption behaviour. One way the model of TMT eould be improved is by using more recent models for sorption isotherms, e.g. that of Choi and Datta [29], or by using conductivity data measured as a funetion of water content. 

Kumar, K. R. and N. Balasubrahmanyam. 1986. Moisture sorption and the applicability of the Brunauer-Emmett-Teller equation for some dry food products. 

Coefficient 5(C) depends on gas condensability as well as polymer-penetrant interactions. Equation (24.2) can be expressed differently using various sorption modes in polymers. These modes, shown in Figure 24.1, are Henry s law sorption, Langmuir-mode sorption, Flory-Huggins mode sorption, dual-mode sorption, and Brunauer-Emmett-Teller (BET) mode sorption. 

The surface area of a solid material is important in that it provides information on the available void spaces on the surfaces of a powdered solid [48]. In addition, the dissolution rate of a solid is partially determined by its surface area. The most reproducible measurements of the surface area of a solid are obtained by adsorbing a monolayer of inert gas onto the solid surface at reduced temperature and subsequently desorbing this gas at room temperature. The sorption isotherms obtained in this technique are interpreted using the equations developed by Brunauer, Emmett, and Teller, and therefore the technique is referred to as the B.E.T. method [49]. The surface area is obtained in units of square meters of surface per gram of material. 

Sorption Analysis. Specific surface areas and porosity can be calculated from the adsorption isotherm of nitrogen at — 196 °C. The method of Brunauer, Emmett, and Teller [4.29] is generally accepted for the evaluation of specific surface areas (BET surface area in square meters per gram). The two-parameter equation is applicable to carbon black. The BET surface area comprises the outer surface area as well as the surface area of the pores. 

Surface area Porosity (pore size, volume, and distribution) BET method (Brunauer, Emmett, and Teller method) Physical gas sorption Chemical gas sorption Helium picnometry Mercury intrusion porometry (MIP)... 

Water vapor adsorption isotherms have been obtained on cotton from room temperature up to 150°C [303,304]. Theoretical models for explaining the water vapor sorption isotherms of cellulose have been reviewed [303]. Only adsorption theories will be discussed here at ambient temperatures. The shape of the isotherm indicates that multilayer adsorption occurs and thus the Brunauer, Emmett and Teller (BET) or the Guggenheim, Anderson and deBoer (GAB) theory can be applied. In fact, the BET equation can only be applied at relative vapor pressures (RVPs) below 0.5 and after modification up to a RVP of 0.8 [305]. The GAB equation, which was not discussed in the chapter in the book Cellulose Chemistry and Its Applications [303], can be applied up to RVPs above 0.9 [306]. Initially as the RVP... 

It is important to realize that useful zeolites have large internal surfaces, that is, a reminder of the sponge analogy, and it is these surfaces that control their observable surface properties. Normally, surface areas of inorganic materials are quantified by standard gas sorption techniques, for example, N2 uptake analyzed by Brunauer, Emmett, and Teller (BET) isotherm plots, and zeolites have nitrogen surface areas in the approximate region 100-1000m g. These estimates should be considered with caution because ... 

Brunauer organized the experimental isotherms observed for vapor sorption into the now classical five groups. Types I to V. Brunauer, Emmett, and Teller ... 

Most subsequent sorption theories, including those discussed here, have followed this general approach and postulate two forms of sorbed water. These theories may be classified into at least two general types based on the sorption mechanism assumed. One type assumes sorption on internal surfaces and is represented by the Dent theory (52), which is a modification of the classic Brunauer, Emmett, and Teller (BET) theory (53). The second type assumes that the wood-water system forms a solution, exemplified by the Hailwood-Horrobin theory. There have been other theories, not discussed here, that have also been applied to explain water sorption by hygroscopic materials (JO, 54, 55). 

We have continued to report BET sorption capacities (expressed as specific surface areas) in light of current practices. Such practice allows us to compare our results to those reported by others where no other measure of sorption capacity is given. This is really a tribute to the landmark work of Brunauer, Emmett, and Teller (8), for providing a comprehensive and useful tool for studying surface phenomena. The fault lies in the application of the theory beyond its realm of applicability. Even the concept of internal surface area derived in this manner is misleading. Actually, the BET sorption capacity is only a measure of the sorption capacity in the region of the knee and probably should be reported in concentration terms (mmol/g, mg/g, cm (STP)/g, etc.) to avoid providing an erroneous concept to the novice. 

Sorption capacities of granular activated carbons and activated carbon fibers were measured, but they were relatively low, e.g., 1 g/g for activated carbon granules with llOOm /g surface area and 19g/g for those with 1220m /g, and no relation to the Brunauer, Emmett, and Teller (BET) surface area was observed. Therefore, the experimental results on different carbon materials showed that macropores, which make bulk density lower, are mainly responsible for their large sorption capacity. Fibrous particles of carbon may be advantageous for easy deformation of macropores to be suitable for sorption of heavy oils. 

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