SEPARATION OF ANIONS BY USE OF THE SURFACE-MODIFIED ANION-EXCHANGE RESIN

The surface of gel-type anion exchange resin was modified by the adsor ption of an anionic polyelectrorite: polycondensation product of sodiu m naphthalene sulfonate and formaldehyde (trade name, Demol N). After the adsorption of the polymer, ion exchange capacity decreased and the rate of ion exchange reaction became slow though ion exchange equilib rium constants between two anions did not changed. Especially, the ion exchange rate of divalent anions was slower than that of the monovale nt anions. Because an anionic polyelectrorite layer was formed on the resin particle, the ion exchange of anions with anion exchange site wa s retarded by sieving effect with the layer and the divalent anions we re difficult to ion exchange compared with the monovalent anion due ti , existence of the opposite charged layer to ion exchange groups. Usin g the modified anion exchange resin in the hydroxide ion form, separat ion of nitrate ion from sulfate ion was attempted. The modified resin was immersed in the mixture solution of nitrate and sulfate ions, and the solution was shaken for definite time. The nitrate ion was prefere ntially adsorbed on the resin. The resin was separated and introduced in the potassium perchlorate solution. After shaking for 90 minutes, t he nitrate ion in the solution was determined by use of ion-chromatogr aph. The separation and enrichment of nitrate ion from 50-fold amount of sulfate ions was accomplished.