Equilibrium and kinetics of nitrate removal by protonated cross-linked chitosan

Nitrate, contained in surface or groundwater, can be removed by sorption on protonated cross-linked chitosan gel beads. The sorption capacity iu pH-de pendent and large enough to meet the standard of drinkable water. The isoth ermal equilibrium curves are straight lines, which implies that the removal is independent of the initial concentration. The main reactive process, wh ich probably depends on the secondary ammonium groups, involves the total b ead volume and not only its surface. If required, the sorption capacity is easily recovered by increasing the pH to 12. The main competitor is fluorid e but,even in its presence the sorption capacity of nitrate remains signifi cant. The sorption kinetics, which can be represented by a mass transfer eq uation, is not limited by pore or by film diffusion.