Adsorption and Absorption

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

Graphical methods at best are simply illustrative for the student today, but they are occasionally referenced by the process engineer. Extraction, like distillation can be viewed as a stage-wise operation, and hence metliods based on the McCabe Thiele approach briefly described in Chapter 4 have been applied to preliminary design cases. Indeed, both absorption and adsorption are stage-wise operations. 

Ultrafiltration utilizes membrane filters with small pore sizes ranging from O.OlS t to in order to collect small particles, to separate small particle sizes, or to obtain particle-free solutions for a variety of applications. Membrane filters are characterized by a smallness and uniformity of pore size difficult to achieve with cellulosic filters. They are further characterized by thinness, strength, flexibility, low absorption and adsorption, and a flat surface texture. These properties are useful for a variety of analytical procedures. In the analytical laboratory, ultrafiltration is especially useful for gravimetric analysis, optical microscopy, and X-ray fluorescence studies. 

Physical treatments scrubbing, settling, absorption and adsorption. 

The absorption and adsorption processes must be designed specifically for each waste-gas system. Most are relatively new processes, and generalized cost data are not available. 

Thus, the preheating of a specimen in an atmosphere of hydrogen (leading to the absorption and adsorption of hydrogen) enhances catalytic activity, as demonstrated by numerous works (30,33-38). 

Calcium—Absorption and adsorption— Congresses. 2. Calcium—Metabolism—Congresses. 

Introduction to absorption and adsorption, scrubbing, stripping, membrane separation, incineration, cdalytic reduction, particulate removal using settling chambers, cydones, electrostatic preepilators, filters, and wet collectors. 

Whilst charcoal possesses this property to a marked extent similar phenomena are to be noted at all solid surfaces. A gas brought into contact with a solid surface will be adsorbed into the surface to- an extent which is dependent on several factors, the nature of the gas and solid, the partial pressure of the gas and the characteristic structure of the exposed surface. This phenomenon of adsorption is, however, frequently complicated by solution of the gas in the solid to form solid solutions or compounds with the solid. The term sorption has been proposed by McBain to include the two phenomena of absorption and adsorption. Our attention will be limited to the characteristics of adsorption. 

A great number of papers devoted to the investigation of hydrogen absorption and adsorption can be found in the literature. Some new developments will be considered here. 

The use of specialized procedures, such as azeotropic and extractive distillation as well as absorptive and adsorptive separations, is another important trend in hydrocarbon fractionation. These processes are discussed in the following section. 

Particular attention should be paid to identifying any high freezing point components in the low-Btu gas. There exists a range of absorption and adsorption processes to pretreat the low-Btu gas to remove these undesirable components. 

Finally, a difference in reduction, absorption and adsorption rate of Ni(II) can be observed between freshly formed and thermolixated PAN fibre. Proof was not found for this effect, but probably the absorption capacity of the thermolixated fibre is reduced, resulting in a decrease in the absorption of Ni(II) in the PAN-fibre structure. 

Absorption The assimilation of a solute, gas, or liquid into the interior of a solid material, an absorbent. Absorption may include the migration of solutes into internal pores or the migration or exchange of atoms within the crystalline structure of a mineral. Some researchers use the generic term sorption to refer to a natural or artificial process where both absorption and adsorption may be involved or if absorption and adsorption cannot be distinguished (compare with adsorption and sorption). 

There are two reasons why artists are particularly vulnerable to diseases caused by exposure to toxic materials. First of all, artists, by the nature of their work, may have daily, long-term contact with materials that are highly toxic. Second, art materials are used as aerosols, powders, dusts, and in solution, from which maximum physical absorption and adsorption are possible. An artist can inhale aerosols. Powders and dusts are also inhaled and, in addition, can be absorbed through the skin. Solutions and many solvents evaporate into the air for the artist to inhale over long periods of time. This chemical assault, day after day, causes a variety of illnesses. In the following section on artists illnesses, all the chemicals cited are used by artists as they draw and paint, sculpt, work with metals, or develop and print photos—in general, as they engage in any art-associated activity. 

Absorption and Adsorption are not the sam e Absorption is the incorporation (sometimes even consumption) of a matter into a medium (light is absorbed/consumed by a pigment, gas is ab-sorbed/dissolves into a liquid), whereas Adsorption is the adhesion of matter onto a—usually solid—surface (dust on furniture, steam on windscreen, vapours on any solid surface...) Adsorption is further subdivided in chemisorption, in which the matter is bound to a surface by chemical bonds, and phy si sorption, in which the bonding is only a physical effect. The transition between both is fluent. 

Sorption general term for physical and chemical absorption and adsorption. 

We begin by defining two important terms absorption and adsorption. The International Union of Pure and Applied Chemistry offers precise definitions for absorption and adsorption (IUPAC, 1972). Absorption is used to describe a process where a component is transferred from one phase to another. Hydrogen gas can be absorbed by LaNis (Jurczyk, 2003). Adsorption is used to describe the increased or decreased concentration of a component at an interface. Water molecules will adsorb to an aluminum oxide surface (Al-Abadleh and Grassian, 2003). The concentration of water molecules on the aluminum oxide surface will be greater than the vapor phase, shown schematically in Figure 3.3. 

One final important fact which comes from Sermon s data is that at 300 K a monolayer coverage is only completed at a hydrogen pressure of 400 Nm. Data for bulk pd shows that at this temperature and pressure hydrogen will have been absorbed up to PdHo.oo4- Here again absorption and adsorption (9 < 1.0) seem to occur simultaneously. 

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