The surface complexation model which so far has been applied to the sorption of ions onto charge-bearing surfaces has been extended to the competitive adsorption of heavy metal salts and strong acids onto weakly basic anion exchanger. Considering local equilibria, logarithmic equilibrium parameters (generalized separation factors) can be deduced by measuring pH values and equilibrium concentrations. The generalized separation factors can be plotted as a function of the dimensionless loadings of the resin phase with metal salts and acids. By this means a set of two equilibrium constants is obtained for the uptake of each component. As found in previous publications about true ion exchange equilibria, it is the major advantage of the theoretical approach that these constants remain unchanged in multicomponent systems. Evaluation of experiments with two commercially available weakly basic anion exchanger products demonstrate the validity of the approach. By means of the parameters derived from simple systems the sorption equilibrium for systems with two heavy metals and systems with additional amounts of neutral salt can be well predicted.

Application of the surface complex formation model to ion exchange equilibria: Part V. Adsorption of heavy metal salts onto weakly basic anion exchangers

The paper critically reviews the existing methods which are applied for the sorption purification of industrial effluents, waste waters and technological solutions from polyvalent metal ions (such as mercury, cadmium, calcium, copper, nickel and zinc), and also describes the novel purification processes developed recently by the authors. Particular attention is paid to the optimization of purification processes through the use of specially selected ion-exchange materials with the optimal equilibrium, kinetic, mechanical and other properties, application of the most effective apparatus design, and optimization of the process flowsheets. The approach proposed is illustrated by the results of both laboratory and the pilot-plant experiments including the final flowsheet of the purification processes. One of the examples given is the tailor-made modification of the commercial VP-1AP polyvinylpyridine resins with l,3-dichlor-5-dimethyl hydantoin, which combines high selectivity and oxidation capability...

Optimization of sorption purification of industrial effluents, waste waters and technological solutions from polyvalent metal ions

The kinetics of mercury removal by a conventional type weak base anion exchange resin, regenerated by sodium sulfide solution was studied. Assuming that the active centers of sulfide regenerated resin are located on the surface of macropores, a mathematical model which explains the extremely high specificity of this resin towards mercury was developed.

I. Dobrevsky

Papers

New Approach on Kinetics of Mercury Removal by Sulfide Regenerated Weak Base Anion Exchange Resin