Purification deionization and color removal

The purification of ionic impurities from aqueous or organic solutions can be performed on ion exchange resins, and non-ionic compounds are adsorb on activated carbon or synthetic adsorbant resin.

The rate of cation removal is depending of the electrical conductivity and the viscosity of the solution to be decationized. The anion removal is less dependant of those parameters, but will be more subject of chemical or mechanical damages, and more dependent on the flow rate.

Some process solutions are hot and a special care will be taken for the anionic resin, especially working in the OH form more subject to thermal degradation than cationic resins or anionic resin in FB form.

Finally, the choice of right resins will also depend on the behavior of the wet resin in contact with the chemical solution, as the resin may swell in some organic solutions.

The color bodies is often acidic and can be efficiently removed from the solution on highly macroporous strong base anionic resins, sometime polished by a final step of activated carbon or synthetic adsorbent having a macroporous polystyrene-DVB matrix offering large pore diameter and surface area. The synthetic adsorbent have the advantage on activated carbons to be easily regenerated on site (steam, alcohol, solvent,) but their capex is more important, and a study on pilot can determine the best solutions: Lenntech can provide studies on column and pilot for such capex/opex optimization.