Conventional Ion-exchange Method Research Articles

In-Situ Precipitation as the Regeneration Step in Ion Exchange for Silver Recovery

The feasibility of in-situ precipitation as the regeneration step in ion exchange for silver recovery is presented. In this step, the silver is precipitated inside the resin instead of eluted with a regenerant. The resin can be reused for many cycles with no decrease in capacity, and the accumulated silver can then be recovered by incinerating the resin. This procedure, like conventional ion exchange, is effective only for effluents containing low thiosulfate concentrations. Effluent silver levels below those of conventional ion-exchange methods have been achieved in our experiments, with the advantage of less supervision and better regeneration control.

AN ANION EXCHANGE RESIN TREATMENT FOR IMPROVING THE TASTE OF COTTAGE CHEESE WHEY

ABSTRACTThe characteristic salty taste of cheese whey was attributed mostly to CaCl2, based on flavor evaluation of individual salts which conform to the milk salt composition. The removal of chlorides using anion exchange resins was investigated to reduce the salty taste of cottage cheese whey. Strongly basic anion exchangers, Rexyn 201 and 202 were more efficient in chloride removal than weakly basic exchangers, Amberlites 45, 68 and 98. Rexyn 202 was preferred to 201 due to requirement of a smaller volume of regenerant. Rexyn 202 regenerated with NaOH alone caused 70% destruction of riboflavin. Rexyn 202 prevented this destruction when regenerated with NaOH then with phosphoric acid; however, the extent of flavor improvement was unsatisfactory although significant. The regeneration of Rexyn 202 with NaOH then with gluconic acid demonstrated best results in terms of flavor improvement. The flavor close to that of the conventional two‐resin method was obtained by this method with almost no losses of Ca and riboflavin from cottage cheese whey compared to 70% and approximately 30% losses of Ca and riboflavin, respectively by the conventional cation‐anion exchange process. Significant flavor improvement of cottage cheese whey was achieved by the single resin column method for desalting, which is simpler than the conventional ion exchange methods using both cation and anion exchange resins.

Amino acid analysis by gas—liquid chromatography of N-heptafluorobutyryl isobutyl esters : Complete resolution using a support-coated open-tubular capillary column

Amino acids have been separated by gas—liquid chromatography as their N-heptafluorobutyryl isobutyl esters. Complete resolution of derivatives of all the common amino acids has been achieved using a high-performance support-coated open-tubular capillary column. The analysis time was 30 min. Modifications to the derivatization procedure of MacKenzie and Tenashuk have been introduced. Acylation by heating at 150° was shown to be destructive; 110° has been selected for routine preparation. To obtain a volatile histidine derivative it has been found necessary to add an antioxidant and to heat samples with ethoxyformic anhydride prior to injection. Amino acid analysis of β-lactoglobulin after 6 N HCl digestion yielded results in good agreement with those obtained by the conventional ion-exchange method. The method has also been successfully applied to estimation of the different caseins in whole casein and in purified fractions by amino acid analysis of residues liberated by carboxypeptidase digestion.

The determination of sodium and potassium after separation from each other and other ions by means of ammonium phosphomolybdate and other ion Exchangers

The separation of sodium and potassium by means of ammonium molybdophosphate (AMP) cation-exchange columns is described. Up to 0.1 meq of potassium can be separated quantitatively from amounts up to 50 meq of sodium on a small (4 g AMP) column. With as much as 0.25 meq of potassium, quantitative separation can be effected by the successive use of two small columns. By a combination of this separation with conventional ion-exchange methods, sodium and potassium can be determined individually in the presence of various other cations.