Synthesis of a Novel Ambipolar Resin Membrane for Ion Adsorption

ABSTRACT

We have synthesized a novel composite ambipolar resin membrane with a high water absorption capacity (150?200%) and superior ion adsorption properties. The ambipolar membrane was capable of adsorbing nitrate, ammonium, potassium and phosphorus simultaneously from aqueous solutions. The adsorption capacity of the membrane varied with ionic concentration and composition. Thus, from a mixed solution of 30 mmol…L^{? 1}NH₄ ⁺ and 10 mmol…L^{? 1} each of NO₃ ^?, K⁺, and H₂PO₄ ^?, the synthetic membrane was able to take up 0.241 mmol NH₄ ⁺, 0.151 mmol NO₃ ^?, 0.120 mmol K⁺, and 0.046 mmol H₂PO₄ ^? per g membrane. A large proportion (73.9?92.5%) of the adsorbed ions could be desorbed with dilute (5%) HCl. The rate of desorption is inversely related to the cross-linking density of the membrane. The competition between NO₃ ^?and H₂PO₄ ^? as well as between K⁺ and NH₄ ⁺ was also investigated.