Adsorption Behavior of 8-Hydroxyquinoline and Its Derivatives on Amberlite XAD Resins, and Adsorption of Metal Ions by Using Chelating Agent-Impregnated Resins

Abstract

Amberlite XAD copolymers have been used as adsorbents for organic substances and as supports for Chelating agent-impregnated resin(CIR). The adsorption mechanism and behavior of 8-hydroxyquinoline (8HQ) and its derivatives on XAD resins have been investigated by interpreting the distribution coefficients (Kd) measured under various conditions. The logKd values of 8HQ and its four derivatives on XAD resins were found to increase up to the certain pH values, and then to decrease with increasing pH. The pH values having maximum logKd values are very close to their isoelectric points. The adsorption of 8HQ and its derivatives was due to molecular adsorption, because the adsorption became maximum when they existed as electrically neutral molecules. Amberlite XAD resins (XAD-2, -4 and -7) impregnated with chelating agents, such as 8HQ, 5, 7-dihalo-8-hydroxyquinoline (DXHQ) and 2-methyl-8-hydroxyquinoline (MHQ), have been applied as CIR resins to the adsorption, separation, concentration and recovery of metal ions (Cu, Cd, Ni, Zn, Pb, Hg and Fe) from the aqueous solutions. All CIR resins show relatively good resistance to leaching at the pH range of 3-10. The magnitude of adsorption capacity of CIR depends on the impregnating capacity of the CIR and the adsorption mole ratio at the optimum pH condition. The metal ions adsorbed by CIR were quantitatively recovered with 3-5M hydrochloric acid. Some examples of selective separation and concentration of metal ions were performed by using CIR resins.