Application of the surface complexation model to heavy metal sorption equilibria onto aminated chitosan

The surface complexation model as previously applied to the sorption of ions onto charge-bearing surfaces has been applied to the simultaneous sorption of heavy metal salts and strong acids onto sorbents prepared from aminated chitosan. From the uptake of metals and acids in simple systems generalized separation factors can be calculated from describing the sorption of anions and cations. Plotting these separation factors vs. the dimensionless loadings of the solid phase with metal salts and with strong acid yields two sets of equilibrium constants describing the sorption. The important feature of the theoretical approach is that these constants remain unchanged in multicomponent systems. Therefore, the prediction of multicomponent equilibria is possible. The method has been demonstrated for systems with copper, nickel, and nitric acid as an example. Evaluation of results reveals a satisfactory agreement between experimental data and predicted equilibria of the ternary system.