Solvent Modified Resin Adsorbents

Unlike carbon however, the polymer adsorbents can be eluted (regenerated) with polar solvents such as methanol, propanone (acetone), electrolytes, or even water. 

Kressman, Properties of Some Modified Polymer Networks and Derived Ion Exchangers , in Ion Exchange in the Process Industries , Society of Chemical Industry, London, 1970, p. 3. 

The Effect of Resin Structure , in Water Purification By Ion Exchange , Butterworths, London, 1968, Ch. 6, p. 99. 

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The foremnner of the modern methods of asphalt fractionation was first described in 1916 (50) and the procedure was later modified by use of fuller s earth (attapulgite [1337-76-4]) to remove the resinous components (51). Further modifications and preferences led to the development of a variety of fractionation methods (52—58). Thus, because of the nature and varieties of fractions possible and the large number of precipitants or adsorbents, a great number of methods can be devised to determine the composition of asphalts (5,6,44,45). Fractions have also been separated by thermal diffusion (59), by dialysis (60), by electrolytic methods (61), and by repeated solvent fractionations (62,63). 

If the chromatographic eluent is a mixture of organic modifier and water and contains no additives such as involatile buffers/acids, then product recovery can be effected simply by removing solvent, e.g., by rotary evaporation. Alternatively, if the solvent volumes are large, the organic modifier can be removed by rotary evaporation and the product recovered by adsorption/elu-tion from a suitable adsorbent such as a reverse phase silica or an organic copolymer resin. This is also a method of choice where additives such as involatile buffers (phosphates, acetates) and acids (orthophosphoric) are present in the fraction and need to be removed. 

An alternative method for modifying or increasing the hydrophilic balance of the resin—without the need to add a third component in the system—has been used [5—7]. In this procedure the extractant is adsorbed directly to the macroporous support after contacting the polymer with a solution of the extractant in a mixture of an organic solvent and water. Mixtures of acetone, methanol, and ethanol with water have been used. Subsequently, the polymer beads are removed from the solution by filtering, and the excess of solvent retained on the polymer is displaced by water, and the SIR is stored in water. Then, the obtained SIR is a three-component... 

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