Adsorption monolayer capacity

Fig. 4.5 Monolayer adsorption capacities of lysozyme onto (A) MCM-41-type mesoporous silicates ((a) MCM-41 and (b) AIMCM-41) and (B) SBA-15-type mesoporous silicates ((a) SBA-15 and (b) AISBA-15). Reprinted with permission from [119],...

Adsorption of lysozyme on these mesoporous carbon materials was studied at a solution pH of 11 [152]. All the adsorption isotherms were of a Langmuir type (see Figure 4.11A), resulting in monolayer adsorption capacities of 3.8, 9.8, 15.9, and 22.9 pmol g 1 for CMK-1, CMK-3, CMK-3-130, and CMK-3-150, respectively. These values are compared with the structural parameters of the CMK materials (Figure 4.11B). There is no clear relation between the adsorption capacity and the surface area (Figure 4.11B(a)). In sharp contrast, positive correlation between the adsorption... 

The effect of pH on the protein adsorption on CMK-3 was also investigated [152], The monolayer adsorption capacities obtained under various pH conditions are plotted in Figure 4.12, where the maximum adsorption was observed in the pH region near the isoelectric point of lysozyme (pi of about 11). Near the isoelectric point, the net charges of the lysozyme molecule are minimized and would form the most compact assembly. A similar pH effect was also seen in the adsorption of cytochrome c on CM K-3. Although the nature of the surface of mesoporous silica and... 

Fig. 6.1.6 (a) Plots of monolayer adsorption capacity of H20 against pretreatment tempera-... 

Doping dodecyl benzene sulfonic acid (DBSA) into PANI/carbon nanotube composite can fabricate PANI/carbon nanotube-DBSA nanocomposite [56]. The preparation, as well as the adsorption to Cr(VI), is depicted in Figure 11.11 with the pseudo-second-order kinetics and Freundlich isotherm model with maximum monolayer adsorption capacity of 55.55 mg/g. Electrostatic interactions between PANI and Cr(VI) anions are the predominant driving forces for this adsorption process. 

Here Cj (mole/cm ) is the amount of vapours adsorbed per unit surface area, (mole/cm ) is the monolayer adsorption capacity, b represent the vapour-solid adsorption interaction parameter, defined as follows ... 

The cross-linked chitosan beads had very high adsorption capacities to remove the anionic dyes whose maximum monolayer adsorption capacity ranges from 1,911 to 2,498 g/kg at 30°C. The adsorption capacities of the cross-linked chitosan beads are mnch higher than those of chitin for anionic dyes. It shows that the major adsorption site of chitosan is an amine gronp-NH, which is easily protonated to form-NH in... 

The experimental steps of chemisorptions of CO and CO2 are as follows after a low-temperature physical adsorption of N2, the sample, under the protection of N2, was quickly transferred to the sample-pool for chemical adsorption, and was vacuumed up to 10 Torr. Then the system was pueged again with helium gas for Ih and vacuumed up to 10 Torr followed by switching gas to CO (CO2) to fill the system. After that, sample-pool was placed in hquid nitrogen (for CO) or dry-ice-alcohol solution (195.2 K) (for CO2) for the measurement of the physical-chemical adsorption (total chemisorption) isotherms (upper-line). Then the physically adsorbed gas was removed, and once again the physical adsorption isotherm was determined (nether-line). The difference of the both monolayer adsorption capacity was regarded as chemical absorption capacity (Fg). Figures 7.14 and 7.15 are typical chemical adsorption isotherm of CO2 and CO, respectively. 

In a related study, Khani (2011) reported on the removal of U ions from aqueous solutions using Padina sp., a brown marine algal biomass. Four main parameters (pH and initial U concentration in solutions, contact time and temperature) were assessed on U uptake. Results showed that the adsorption data adequately fitted a second-order polynomial model. The optimum pH and initial U concentration in solutions, contact time and temperature were found to be 4,778 mg L , 74 min, and 37°C, respectively. The maximum U uptake was predicted and experimentally validated. The maximum monolayer adsorption capacity was found to be as high as 376 mg g . ... 

Types of physisorption isotherms.The point B refers to monolayer adsorption capacity from which the surface area of the sample can be determined. (Reprinted from Sing etal., 1985.)... 

A commonly used method of determining the specific surface area of a solid is by the adsorption of a gas onto the solid and the determination of the monolayer capacity. Most methods make use of the Brunauer, Emmett, and Teller equation, commonly referred to as the BET equation, for calculating the surface area on the basis of monolayer adsorption. The BET equation can be written as... 

The number of gas molecules can be measured either directly with a balance (gravimetric method) or calculated from the pressure difference of the gas in a fixed volume upon adsorption (manometric method). The most frequently apphed method to derive the monolayer capacity is a method developed by Brunauer, Emmett, and Teller (BET) [1], Starting from the Langmuir equation (monolayer adsorption) they developed a multilayer adsorption model that allows the calculation of the specific surface area of a sohd. The BET equation is typically expressed in its linear form as... 

Silica gel is a polar material. The presence of silanol groups is responsible for the acidic catalytic effect of this material (the pK of Si OH is comparable to that of phenol). The mode of action of silica gel is based on adsorption (Fig. 3.9), a phenomenon that leads to the accumulation of a compound at the interface between the stationary and mobile phases. In the simplest case, a monolayer is formed (known as a Langmuir isotherm) but there is also some attraction and interaction between molecules that are already adsorbed and those still in solution. This contributes to the asymmetry of the elution profile. Although it demonstrates good resolution and a high adsorption capacity, bare silica gel is seldom used for analytical purposes. For most applications, it must be deactivated by partial rehydration (in 3-8% water). 

The ethylene adsorption capacity increases with the content of CuCl and reaches the highest value at the point near the monolayer dispersion threshold. Similar plots have been reported by Zhao et al. (57) in the investigation of ethylene adsorption on Cu0/y-Al203 and by Duan et al. 

For open surfaces, adsorption consists of a layer-by-layer loading process, where the first layer is filled as in the case when 9 = nJNm = 1, where 9 is the surface recovery and Nm is the monolayer capacity. As a result, it is understood that we have monolayer adsorption when 9 = nJNm < 1, and multiplayer adsorption when 9 = nJNm > 1. 

Indeed, if the methane molecule is supposed to act similar to a spherical molecule, its diameter is 0.381 nm hence, pores that have widths, L, of less than approximately 1 nm can house only one monolayer, while those narrower than around 0.4nm cannot store methane at all [186], If wider pores are considered, the attractive potential produced by the facing pore walls diminishes very fast with the value of the pore width, L, so that, if L > 3-4 nm, methane is weakly adsorbed, and its density is comparable to that of the gas phase in equilibrium with it. Subsequently, it is obvious that the maximum adsorption capacities are achieved with materials for which the volume of pores that have the pertinent width is the maximum [200,202], As a result, active carbons having slit-shaped pores may be the best material for methane adsorption [187],... 

Bulatnikov et al. (340) studied the effects of promoters on sulfur resistance of iron by measuring the amount of radioactive H2S adsorbed on iron catalysts promoted with A1203 and/or K20. They reported irreversible deactivation of Fe promoted with A1203, A1203 + K20, or KzO after 0.8, 1.5, and 5 monolayers of sulfur had been adsorbed. In other words, the presence of K20 was responsible for increasing sulfur adsorption capacity, although it was not clear upon which portion of the surface sulfur had adsorbed. It was also reported that A1203 was necessary to prevent volatilization of K20. 

Fig. 9.9. Relationship between HD5 activity and CoMo loading. Fixed Y-AI2O3 support, fixed Co/Mo atomic ratio. Aindicates monolayer coverage of the support by Mo — indicates Mo-adsorption capacity of the Y-AI2O3 applied when using the impregnation solutions indicated.

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