Batchwise adsorption

Membrane proteins to be purified have to be solubilized from cells or from the envelope of virions. The most commonly used lysis or extraction buffer is lOmM Tris-HCl, pH 7.6-7.8, supplemented with 0.10-0.15 M NaCl and 1-2% Triton X-100 or NP-40. Sometimes deoxycholate (up to 0.5%), 0.6 M KCl, and 0.5 mM MgCl2 are added as well. To avoid proteolytic degradation during the extraction procedure, protease inhibitors such as phenylmethylsulfonyl fluoride (PMSF), EDTA, and aprotinin are added. After extraction, insoluble residues are removed by ultracentrifugation or by filtration, and the extract is then applied to the immunoadsorbent column. In some cases, it may be preferable to perform the adsorption batchwise and to pack the column afterward. 

Resias are seldom used oace and discarded. Whether the system is mn batchwise or ia columns, the resia must be periodically removed from service and regenerated. An exception is the use of a resia as a catalyst ia organic reactions. Each cycle consists of two principal steps, adsorption and regeneration, and one or more iatermediate steps, tinse and backwash. Eailure to use good practices results ia poor cycHc performance. 

Although PSA is a batchwise process, by using multiple beds in a sequential manner the overall process is operated in a continuous fashion. Each bed may contain layers of different adsorbent materials selective for specific contaminants in the hydrogen gas stream to be purified. Each bed undergoes a sequence of four basic steps in a PSA cycle adsorption, depressurization, purge at low pressure, and repressurization. This sequence of cyclic operations for each bed is shown schematically for a four-bed PSA process in Figure 8.4 (Yang, 1987 Cassidy, 1980 Miller and Stocker, 1999). 

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. 

Ceruloplasmin (from human blood plasma) [9031-37-2]. Purified by precipitation with polyethylene glycol 4000, batchwise adsorption and elution from QAE-Sephadex, and gradient elution from DEAE-Sepharose CL-6B. Ceruloplasmin was purified 1640-fold. Homogeneous on anionic polyacrylamide gel electrophoresis (PAGE), SDS-PAGE, isoelectric focusing and low speed equilibrium centrifugation. [Oestnuizen AB 146 1 1985]. 

Fractional extraction242 (dissolution) may also be employed, as was demonstrated for a polyxylose, using batchwise extraction with aqueous ethanol.141 A more convenient procedure would involve adsorption of the polyglycose onto an inert, solid support (such as cellulose), followed by extraction using a procedure already described.243 The continuous nature of this process, the opportunity for solvent to reach all particles of the polymer, and the possibility of using gradient elution make this method attractive, particularly if the examination of a range of polymeric distributions is desired. 

Among hybrid separations not involving membranes, adsorptive distillation (87) offers interesting advantages over conventional methods. In this technique a selective adsorbent is added to a distillation mixture. This increases separation ability and may present an attractive option in the separation of azeotropes or close-boiling components. Adsorptive distillation can be used, for instance, for the removal of trace impurities in the manufacturing of fine chemicals (it may allow for switching some fine chemical processes from batchwise to continuous operation). 

Batchwise adsorption is usually used for a final purification prior to the isolation of the desired compound and is most commonly used for decolorizing compounds. Colored compounds usually have many conjugated double bonds and thus are adsorbed in preference to many colorless compounds. Charcoal is commonly used as an adsorbent, since it is particularly effective in adsorbing the aromatic compounds which are often the colored impurity. Batchwise adsorption is also used to remove impurities which may inhibit crystallization or produce foaming in a distillation. 

Fig. 2 Effects of a buffer s (a) ionic strength and (b) pH on th adsorption of LPS by various aminated cellulose adsorbents. Th adsorption of LPS was determined using a batchwise methoc with 0.2 g of the wet adsorbent and 2 mL of a LPS (E. coIm 0111 B4, 1000 ng/mL) solution. Adsorbent and AEC oS adsorbent PEl-cellulose=poly(ethyleneimine)-i mmobi li zedE CeUufine-GC15 (AEC 1.2 meq/g) PL-cellulose=poly( -ly-i sine)-immobibzed CeUufine-GC15 (AEC 0.6 meq/g) DAH- cellulose=diaminohexane-immobibzed Cellufme-GC15 (AECig, 0.2 meq/g). of adsorbent 2 x 10 .

Fig. 4 Effects of ionic strength on selective adsorption of EPS from a BSA solution containing EPS by the various aminated cellulose adsorbents reported in Pig. 2. The selective adsorption of EPS was determined by a batchwise method with 0.2 g of the wet adsorbent and 2 mL of a sample solution [BSA 500 pg/mL, EPS E. coli 0111 B4) 100 ng/mL, pH 7.0, and ionic strength of p=0.05-0.8].

Hazardous residual left from previous cycle in batchwise adsorption, IX... 

The rate of equilibrium attainment mainly during the batchwise arrangement is strongly affected by the concentration of a substance to be isolated in the sorption solution. Fig. 4.7.6 shows the rate of adsorption of trypsin on to soybean trypsin inhibitor-agarose particles in suspensions in solutions containing equal amounts of trypsin but of a different concentration [129]. The rate of sorption is determined on the basis of the residual activity of trypsin measured at various time intervals. 

According to the previous chapters the reader may come to the conclusion that countercurrent columns are dominant as has been shown for mass transfer equipment used in the areas of rectification, absorption, and extraction. However, this is not true because the continuous transport of solid granular material is much more difficult in comparison to a fluid. Therefore, nearly all adsorbers are fixed beds which are operated batchwise. As a rule, at least two fixed beds are installed in continuously operated industrial processes. The first bed is used for the adsorption step whereas in the second the adsorbates is removed or desorbed at the same time. The duty of the two beds is changed when the adsorption capacity is exhausted. Sometimes several beds are arranged to cany out pressurization and depressurization steps. 

The cellulose phosphate was widely applied in the removal process of divalent and trivalent (Cu ", Zn ", Co, Ni, Pb ", Mn ", Fe, Fe , Cr ) ions because of the rapid adsorption of the metals ions in comparison with the synthetic polymers. Also it was observed that the cellulose phosphate functions as an ion exchanger for lanthanide ion removal from aqueous solution. In order to evaluate the adsorbent characteristics of each support in the removal process of metal ions from aqueous solution, the most widely used method by researchers has been the batchwise one. In any adsorption process the most important parameter is the pH of the medium, which depends on the nature of the support used and also on which metal ions are to be removed. In most cases, researchers worked with solutions that have an acid pH value in order to avoid the possible precipitation of the studied metal ions. A complex study of the pH influence upon the efficiency of Fe ", Cu ", Mn, Zn, Co ", and lanthanide(III) ions removal from aqueous solutions with PBC was made by Oshima et al. Their conclusion was that the lanthanide ions are adsorbed when the pH value of the aqueous solution is less than 3, and in the case of transition metal ions the adsorption percentage increases with increasing aqueous pH and reaches over 90% at a pH value of around 4.5. 

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