Adsorption liquid, from gases

It must be remembered that, in general, the constants a and b of the van der Waals equation depend on volume and on temperature. Thus a number of variants are possible, and some of these and the corresponding adsorption isotherms are given in Table XVII-2. All of them lead to rather complex adsorption equations, but the general appearance of the family of isotherms from any one of them is as illustrated in Fig. XVII-11. The dotted line in the figure represents the presumed actual course of that particular isotherm and corresponds to a two-dimensional condensation from gas to liquid. Notice the general similarity to the plots of the Langmuir plus the lateral interaction equation shown in Fig. XVII-4. 

Activated carbons for use in Hquid-phase appHcations differ from gas-phase carbons primarily in pore size distribution. Liquid-phase carbons have significantly more pore volume in the macropore range, which permits Hquids to diffuse more rapidly into the mesopores and micropores (69). The larger pores also promote greater adsorption of large molecules, either impurities or products, in many Hquid-phase appHcations. Specific-grade choice is based on the isotherm (70,71) and, in some cases, bench or pilot scale evaluations of candidate carbons. 

Ordinary diffusion involves molecular mixing caused by the random motion of molecules. It is much more pronounced in gases and Hquids than in soHds. The effects of diffusion in fluids are also greatly affected by convection or turbulence. These phenomena are involved in mass-transfer processes, and therefore in separation processes (see Mass transfer Separation systems synthesis). In chemical engineering, the term diffusional unit operations normally refers to the separation processes in which mass is transferred from one phase to another, often across a fluid interface, and in which diffusion is considered to be the rate-controlling mechanism. Thus, the standard unit operations such as distillation (qv), drying (qv), and the sorption processes, as well as the less conventional separation processes, are usually classified under this heading (see Absorption Adsorption Adsorption, gas separation Adsorption, liquid separation). 

Activated carbon is an amorphous solid with a large internal surface area/pore strucmre that adsorbs molecules from both the liquid and gas phase [11]. It has been manufactured from a number of raw materials mcluding wood, coconut shell, and coal [11,12]. Specific processes have been developed to produce activated carbon in powdered, granular, and specially shaped (pellet) forms. The key to development of activated carbon products has been the selection of the manufacturing process, raw material, and an understanding of the basic adsorption process to tailor the product to a specific adsorption application. 

Adsorption is the process by which liquid or gaseous molecules are concentrated on a solid surface, in this case activated carbon. This is different from absorption, where molecules are taken up by a liquid or gas. Activated carbon can made from many substances containing a high carbon content such as coal, wood and coconut shells. The raw material has a very large influence on the characteristics and performance activated carbon. 

Activated Carbon for Process Water Treatment Activated Carbon from CPL Carbon Link - Activated carbon from CPL Carbon Link for liquid and gas phase purification by adsorption. Activated carbons for all applications including chemical, water, air, solvent recovery, gold recovery, food, automotive, industrial, catalysis.. http //www.activated-carbon.com. 

Adsorption/desorption-molecules or fragments from gas or liquid bond to solid surface. 

When an adsorbing surface is exposed to a gas or vapour adsorption will take place, being accompanied by the absorption or evolution of heat. Such thermal changes have already been noted in the extension and contraction of surface films of liquids. Although the direct determination of the surface energy of solid surfaces presents many experimental difficulties yet of its existence there is no doubt. On the adsorption of a gas or vapour a diminution in the free surface energy of the system likewise occurs. From the Gibbs-Helmholtz relationship dcr... 

Adsorption is a physical phenomenon in which some components adsorbates) in a fluid (liquid or gas) move to, and accumulate on, the surface of an appropriate solid adsorbent) that is in contact with the fluid. With the use of suitable adsorbents, desired components or contaminants in fluids can be separated. In bioprocesses, the adsorption of a component in a liquid is widely performed by using a variety of adsorbents, including porous charcoal, silica, polysaccharides, and synthetic resins. Such adsorbents of high adsorption capacities usually have very large surface areas per unit volume. The adsorbates in the fluids are adsorbed at the adsorbent surfaces due to van der Waals, electrostatic, biospecific, or other interactions, and thus become separated from the bulk of the fluid. In practice, adsorption can be performed either batchwise in mixing tanks, or continuously in fixed-bed or fluidized-bed adsorbers. In adsorption calculations, both equilibrium relationships and adsorption rates must be considered. 

We have also added for comparison in Column 2 of Table 1 the date of Sidorov [10] which indicate the shifts of the fundamental rOH band of porous glass upon adsorption of the same compounds from gas. In Column 4 [14] we compare our data with those obtained by Mecke for the shifts of the second overtone (3rOH) band of phenol dissolved in the same liquids. In the last column of the Table the shifts of the fundamental OH frequency of methanol, dissolved in the same solvents... 

Englezos et al. (1987a,b) generated a kinetic model for methane, ethane, and their mixtures to match hydrate growth data at times less than 200 min in a high pressure stirred reactor. Englezos assumed that hydrate formation is composed of three steps (1) transport of gas from the vapor phase to the liquid bulk, (2) diffusion of gas from the liquid bulk through the boundary layer (laminar diffusion layer) around hydrate particles, and (3) an adsorption reaction whereby gas molecules are incorporated into the structured water framework at the hydrate interface. 

Many processes have been developed for the removal of hydrogen sulfide from gas streams. They can be classified as liquid absorption, liquid oxidation, dry oxidation, and adsorption. One of these processes is usually included in a coal gasification or liquefaction flowsheet since the coal sulfur is converted to H2S and finally elemental sulfur. The Stretford and Townsend direct HpS to S processes and the Recti sol process followed by a Claus plant are frequently included on coal conversion flowsheets (1 ). Kohl and Riesenfeld (2) present pertinent details for many commercial processes. 

Adsorbate A contaminant or other substance that is removed from its host liquid or gas through adsorption onto an adsorbent. 

The pore volume and the pore size distribution can be estimated from gas adsorption [83], while the hysteresis of the adsorption isotherms can give an idea as to the pore shape. In the pores, because of the confined space, a gas will condense to a liquid at pressures below its saturated vapor pressure. The Kelvin equation (Eq. (4.5)) gives this pressure ratio for cylindrical pores of radius r, where y is the liquid surface tension, V is the molar volume of the liquid, R is the gas constant ( 2 cal mol-1 K-1), and T is the temperature. This equation forms the basis of several methods for obtaining pore-size distributions [84,85]. 

The traditional application of adsorption in the process industries has been as a means of removing trace impurities from gas or liquid streams. Examples include the removal of H2S from hydrocarbon streams before processing, the drying and removal of C02 from natural gas, and the removal of organic compounds from waste water. In these examples the adsorbed component has little value and is generally not recovered. Such processes are generally referred to as purification processes, as distinct from bulk separations, in which a mixture is separated into two (or more) streams, each enriched in a valuable component, which is recovered. The application of adsorption to bulk separations is a more recent development that was stimulated to a significant extent by the rapid... 

In this chapter, we have so far discussed the adsorption of gases in solids. This section gives a brief description of the adsorption process from liquid solutions. This adsorption process has its own peculiarities compared with gas-solid adsorption, since the fundamental principles and methodology are different in almost all aspects [2,4,5], In the simplest situation, that is, a binary solution, the composition of the adsorbed phase is generally unknown. Additionally, adsorption in the liquid phase is affected by numerous factors, such as pH, type of adsorbent, solubility of adsorbate in the solvent, temperature, as well as adsorptive concentration [2,4,5,84], This is why, independently of the industrial importance of adsorption from liquid phase, it is less studied than adsorption from the gas phase [2],... 

Absorption of harmful organic compounds by activated carbons from gas and liquid media is of interest and importance for human and environmental protection purposes.1"21 The influence of the texture of carbon granules (size and volume of pores, specific surface area, granule size d, and carbon bed depth V), gas stream humidity and velocity, and amounts of pre-adsorbed water are investigated on adsorption of organics in different media.1 21... 

Figure 3.17. Temperature (left) and amount of adsorptive in the gas phase (hatched area, right) as one moves from bottom to top cf an adsorption bulb immersed in liquid nitrogen.

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