Copper (II) Ion–Exchange Properties of Free–Standing Alginate Membrane

Abstract

The insolubilized alginate membrane was obtained by drying the soluble alginate solution, followed by crosslinking with calcium ion. The alginate membrane had smooth surface and applicable mechanical strength for practical use. Isothermal ion–exchange adsorption of Cu²⁺ in batch process was conducted on alginate membranes obtained. The result was consistent with the Langmuir type isotherm, and the Cu²⁺ ion–exchange capacities were estimated by fitting of the experimental data. It was found that the ion–exchange capacity of the alginate membrane was equivalent to alginate gel beads. For an improvement of water permeability, polyethylene glycol was added in the casting solution before drying process, and then, was removed from the prepared membrane. The permeation flux of the membrane was determined from the amount of pure water permeated under pressure and its value increased with the amount of polyethylene glycol added in the casting solution. An in–line removal experiment using the prepared membranes was also attempted and succeeded in removing Cu²⁺ ion under flowing condition. In addition, novel calcium alginate membrane embedded with zeolite as an ion–exchange material was successfully prepared for heavy metal ions removal from aqueous phase.