Using NaCl particles as porogen to prepare a highly adsorbent chitosan membranes

Macroporous chitosan membranes were prepared by using NaCl particles porogen and genipin as cross-linking agent. For characterization and sorption behavior comparison, other genipin cross-linked chitosan membranes were prepared by either freeze drying or by using silica particles as porogen. The mean pore diameter, the porosity, the crystallinity index (CrI) as well as the effect of the drying procedures of these chitosan membranes were examined. NaCl reduced the CrI of the chitosan membrane. The oven drying (OD) procedure decreased the mean pore diameter, the porosity, and increased the CrI of the chitosan membranes when compared with the vacuum drying (VD) procedure. The heat treatment of chitosan membrane in aqueous NaOH to attract silica porogen increased the CrI of the membrane. Under the same conditions, the membranes prepared with NaCl had better sorption performance on RR 189 and Cu²⁺ than other membranes. The maximum sorption capacity (q_e) reached 1836.17 mg RR 189/g chitosan and 151.98 mg Cu²⁺/g chitosan. The pore diameter (d_pore) of the membranes was much larger than the diameter of the adsorbate molecules (d_adsorbate), such that the ratio of d_pore/d_adsorbate had little influence on q_e. The porosity and the amorphous extent of the membranes were almost the same on q_e. When using tyrosinase catalyzing, the hydrocaffeic acid (HCA) grafted on the NaCl treated chitosan membrane was almost 10 times more than on chitosan beads. The chitosan membrane prepared with NaCl can be used as a good adsorbent with high loading capacity for implanting molecules (such as ligands, enzymes, etc.) on.