Chitosan-calcium carbonate composites: Biomimetic mineralization of aqueous carbonate ions into chitosan-ca1cium alginate hydrogels

Two hydrogels of calcium alginate and chitosan-ca1cium alginate composite were prepared from Na alginate and its composite with chitosan by soaking in 0.1M aq. CaCl 2 . A biomimic fixation of aqueous CO 3 2- ions as CaCO 3 was performed. Each of the hydrogels was put into a dialysis membrane tube, and was soaked in 0.1 M aq. Na 2 CO 3 (pH 11) at room temperature for 1 day to afford a white precipitate of CaCO 3 or chitosan-CaCO 3 and a water-soluble sodium alginate. The dry chitosan-CaCO 3 composite (60% chitosan and 23% CO 3 2 ) was stable in aqueous alkaline solutions and unstable in aqueous acidic solutions.