Anion exchangers, adsorbability

A conversion degree of the anion exchanger into the sulphite-hydroxyl forms depends on the SO2 concentration in a gas flow (Fig. 7). At concentrations of 50 mg/m < CgQ < 650 mg/m, the anion exchanger adsorbs from 0.5 to 0.95 mole of S02/eqv., which corresponds to a mixed HSOg — SO -form. With decreasing SO2 concentration, below 50 mg/m, less than 0.5 mole of S02/eqv. is absorbed which corresponds to the mixed hydrocarbonate-sulphite form. 

Tongta, A. Liapis, A.I., and Hagen, S., Synthesis of anion exchange adsorbent particles by surface functionalization of polystyrene-divinylbenzene based spherical porous matrices, Sep. Technol., 6(1), 77-90 (1996). 

Li, Q, Xing, J., Li, W, Liu, Q, and Su, Z. (2009) Separation of succinic acid from fermentation broth using weak alkaline anion exchange adsorbents. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

Ion Excha.nge, The recovery of uranium from leach solutions using ion exchange is a very important process (42). The uranium(VI) is selectively adsorbed to an anion-exchange resin as either the anionic sulfato or carbonato complexes. In carbonate solutions, the uranyl species is thought to be the tris carbonato complex, U02(C03) 3 [24646-13-7] and from sulfate solutions the anion is likely to be U02(S0 , where nis ) [56959-61-6] or 2 [27190-85-8], The uranium is eluted from the resin with a salt or acid solution of 1 AfMCl or MNO (M = H", Na", The sulfate solution is... 

Anion A negatively charged ion in an electrolyte solution, attracted to the anode under the influence of a difference in electrical potential. Chloride is an anion. Anion exchange capacity Sum total of exchangeable anions that a soil can adsorb. Expressed as centimoles of negative charge per kilogram of soil. 

Highly active catalysts have been produced by adsorption of lipases onto macroporous acrylate beads, polypropylene particles and phenol-formaldehyde weak anion exchange resins. Protein is bound, presumably essentially as a monolayer, within the pores of the particles. The large surface area of the particles (10m2 g 1) means that substantial amounts of protein can be adsorbed, and the pores are of sufficient size to allow easy access of reactants to this adsorbed protein. 

Step 4. Anion-exchange chromatography on a column of DEAE-Sephadex A-50. The column had been equilibrated with the basic buffer containing 0.12 M NaCl. The NaCl in the photoprotein solution was removed by gel filtration, and then the solution was added onto the column. The photoprotein adsorbed on the column was eluted with the equilibration buffer. 

The ion-exchange process consists of adsorbing these anionic complexes selectively and quantitatively on an anion-exchange resins as illustrated in the following reactions ... 

Purification of double-stranded DNA on micropellicular anion exchange and reversed-phase materials has been reviewed.43 Micropellicular phases adsorb only at the surface and have no internal pores. For this reason, the surface area and hence the capacity of micropellicular phases tends to be low. Using small particles (1-3 p in diameter) increases the surface area but may be impractical for preparative work above the mg scale. 

Figure 15.4(A) shows the effect of the R = Zn2+/Al3+ ratio, which determines the charge density of the LDH layer, on the Freundlich adsorption isotherms. K values are far higher than those measured for smectite or other inorganic matrices. The increase in Kf with the charge density (Kf= 215, 228, 325mg/g, respectively, for R = 4, 3 and 2) is supported by a mechanism of adsorption based on an anion exchange reaction. The desorption isotherms confirm that urease is chemically adsorbed by the LDH surface. The aggregation of the LDH platelets can affect noticeably their adsorption capacity for enzymes and the preparation of LDH adsorbant appears to be a determinant step for the immobilization efficiency. [ZnRAl]-urease hybrid LDH was also prepared by coprecipitation with R = 2, 3 and 4 and Q= urease/ZnRAl from 1 /3 up to 2.5. For Q < 1.0,100 % of the urease is retained by the LDH matrix whatever the R value while for higher Q values an increase in the enzyme/LDH weight ratio leads to a decrease in the percentage of the immobilized amount.

The adsorbent should have a high affinity and capacity for the enzyme and it should not absorb the reaction product or enzyme inhibitors. Among the materials used the more popular are cation and anion exchange resins, activated charcoal, silica gel, alumina, control pore glasses and ceramics. 

Anion exchange resins have been used to determine extremely low concentrations of nitrite down to nanomoles in seawater. Wada and Hattori [148] formed an azo dye from the nitrite using N-1 naphthylethylene diamine dihydrochloride and then adsorbed the dye in an anion exchange resin. The dye is then eluted from the column with 60% acetic acid and measured spec-trophotometrically at 550 nm. 

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