Separation of anions from aqueous and mixed aqueous solvents using strong base and weak base anion exchangers

Batch-wise sorption tests were carried out to evaluate the ability of strongly basic and weakly basic anion exchangers in chloride form to separate perchlorate, thiocyanate, iodide and nitrate anions from water/2-isopropoxy ethanol mixed media. The initial large difference observed in the selectivity magnitudes of ClO4-, CNS-, I- and NO3- decreased with increasing concentration of 2-isopropoxy ethanol. The higher selectivity of these anions on macroporous resins was attributed to higher degree of cross linkage. The addition of 2-isopropoxy ethanol changes the magnitude of solvation free energy of ions by replacing some of the water molecules in the coordination sphere. The important change observed in selectivity was due to significant reduction in dielectric constant of the medium from that of pure water to 80% 2-isopropoxy ethanol composition.