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.