Info

Percent Divinylbenzene

Figure 13. Average pore diameter of sulfonic acid cation exchange resin as a function of degree of cross-linking. (Ref. 20, page 46)

Percent Divinylbenzene

Figure 13. Average pore diameter of sulfonic acid cation exchange resin as a function of degree of cross-linking. (Ref. 20, page 46)

0 1 8 12 16 Percent Divinylbenzene

Figure 14. Average pore diameter of carboxylic acid cation exchange resin as a function of degree of cross-linking. (Ref. 20, page 47)

Figure 15. Ion diffusion coefficients in macroporous sulfonated cation exchange resins.[58' (1) Tetramethyl; (2) tetraethyl; (3) tetrabutyl ammonium ions.

Since each bead of a given external diameter that is made by the inert diluent process will contain some void volume, there is actually less polymer available per unit volume for the introduction of functional groups. Therefore, these macroporous resins are inherently of lower total exchange capacity than gel-type resins of the same composition.

Macroporous resins are most useful when extremely rigorous osmotic shock conditions are encountered, when the very high porosity is desirable from the stand point of the molecular weight of the material being treated or when nonpolar media are involved. The drawbacks of using macroporous resins are poorer regeneration efficiencies, lower total exchange capacities and higher regeneration costs.

Until the advent of macroporous resins, the synthetic organic ion exchange resins were of such low porosity that large proteins and other macromolecules would be adsorbed or interact only with the exterior exchange sites on the resins. Therefore, although the microporous resins may have higher total exchange capacities than macroporous resins, the effective capacity of macroporous resins for protein or macromolecule adsorption may often times be greater than that of microporous resins.

Typical macroporous ion exchange resins may have average pore diameters ranging from 100 A to 4000 A. Table 11 shows the pore sizes of several "resins of different matrices that have been used in enzyme immobilization.[61] Pore volumes for macroporous resins may range from 0.1 to 2.0 ml/g.

Table 11. Physical Properties and Capacities for Ion Exchange Resins1611

Adsorption

Table 11. Physical Properties and Capacities for Ion Exchange Resins1611

Adsorption

Resin Matrix

Functionality

Pore Size

Surface Area

Resin Capacity

Capacity for Enzyme

phenolic

3° polyethylene polyamine

Was this article helpful?

0 0

Post a comment