Sorbent materials, characteristics

From the discussion so far it follows that sorption as well as diffusion play a role. Their relative importance depends on such sorbent material characteristics as pore size, sorption strength, and gas properties such as molecular size and shape, concentration, etc. 

Sorbent Material stable against radiation, preferably inorganic Nontoxic Insoluble Good mechanical properties Good packing and flow characteristics (of the column) Easy to prepare and handle Very strong binding of parent isotope, preferably total immobilization... 

All of the disadvantages of throwaway flue gas treatment systems can be lessened considerably by minimizing the amount of waste material produced. This can be accomplished by the choice of an effective sorbent material and the use of sorbent recycle to increase utilization. In turn, sorbent recycle can be optimized by the use of a separation process to remove the spent sorbent from unreacted sorbent. As water usually contributes significantly to the mass of the waste produced, the dewatering characteristics of the waste material are important. Efficient dewatering will not only minimize water losses but also reduce the disposal space required. 

The chemical and physical characteristics of the sorbent materials as well as those of the heavy metals vary widely and it is difficult to recommend specific low-cost materials for specific pollutants. There is a necessity of experimental work with different materials and different heavy metals in order to understand the variations in the sorption phenomena. This paper presents the results of comparative equilibrium studies performed using activated carbon and natural zeolite. Three heavy metals, Zn(II), Cd(II) and Pb(II), from aqueous solutions as adsorbats were used. 

As briefly introduced in the previous sections, the sorbent is the most important component in an enhanced reactor since it determines the reactor design and the performance of the process. The sorbent material must have the following characteristics ... 

Consequently, the helium volume of a sorbent material can be considered as one of its characteristic quantities describing that volume of the material impenetrable for helium molecules on a short time scale of minutes, may be hours. It seems to be kind of lower boundary to the sorbent volumes impenetrable to other, bigger molecules. 

An instrument to measure the dielectric permittivity of a gas adsorption system basically consists of an electric capacitor (plates, cylinders, spheres) placed within an adsorption vessel. The vessel should be placed within a thermostat (water, oil etc.) and provided with tubes for gas supply and evacuation. Also manometers and thermometers are needed to measure the gas pressure (p) and temperature (T) inside the chamber. The capacitor is filled with sorbent material (powder, pellets, continuous matter etc.) which can be considered to be homogenous as long as its characteristic length - for example the diameter of cylindrical pellets - is small compared to a characteristic length of the capacitor. 

Here po is the density of the sorptive medium in a reference liquid state which may be chosen as the density of the saturated boiling liquid at the chosen temperature, i. e. po = Ps (T), [7.5, 7.3]. The parameter a in the characteristic curve of the sorbent material (7.78) is the reciprocal of a specific energy the exponent N normally is limited to 2 < N < 6 and for zeolites and activated carbons often has numerical values about N = 3. Both parameters are characteristic for a sorbent material and the micropore spectrum included in it. Details of practical applications of (7.79) and a variety of generalizations to real gas adsorptives and multicomponent systems can be found in the (still growing) literature in this field [7.53 7.55, 7.58]. 

For example, Ronco [48] suggested the possibility of mixing the biomaterial of a specific membrane with a sorbent material based on a significant enhancement of internal and backfiltration in hollow-fiber hemodialyzers. Thus, the single membrane will have both characteristics, i.e., diffusion and adsorption for removal of uremic acid, and is called mixed matrix membrane (MMM) [49,50]. The MMM concept had been proposed earlier as an alternative to traditional chromatographic column [51]. 

GPC separations require an interaction-free phase system. The separation efficiency in GPC is proportional to the pore volume, which limits the decrease in column dimensions. In many cases, GPC analyses are performed on serial combinations of columns. In most applications, silica and surface-modified silica columns do not meet the requirements for GPC columns and polymeric packings are preferred. Important characteristics for GPC column packings are the inertness of the sorbent material (chemistry), the accessibility of the pore structure, a high pore volume, and fast diffusion (optimal mass transfer) [la). 

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