ON THE SORPTION OF ANIONS BY FERRIC-OXIDE GEL .1. AQUEOUS-MEDIUM

Sorption studies of SO42-, Cl-, Br- and NO3- ions on ferric oxide gel have shown that these ions replace surface OH groups. The particle dif fusion-controlled exchanges follow mainly the Helfferich first mechani sm. This situation is different from that in weak-base resins in the s imilar case of ionization of weakly dissociated groups by reaction wit h H+ co-ions. The interdiffusion coefficient D(i)BAR decreases in the order SO42- > Cl- > Br- > NO3-. It was deduced that, at least for SO42 -, the complexing ability with Fe(III) at the gel/water interface is w eaker than that in solution.