| Chitosan（CS） has been widely used in areas such as food,pharmacy, material and environmental protection because of its biocompatible, biodegradable, antibacterial and adsorptive characterics. However, the applications of chitosan served as functional fibers are limited due to its low strength and easy swelling. Furthermore, it is difficult to fabricate pure chitosan nanofibers because of its low solubility, high viscosity and electrostactic repulsions between cationic polyelectrolyte chains in acidic aqueous solvent. Blending is an efficacious way to improve electrospinnability and mechanical property of chitosan. In this work, CS/PVA nanofibrous membranes were prepared by electrospinning CS/PVA in acetic acid aqueous solvent. The air filtration properties of CS/PVA nanofibrous membranes were studied, and CS/PVA/CaCO3 hybrid nanofibrous membranes were prepared.Firstly, the optimal electrospining conditions were developed to prepare CS/PVA nanofibers. The effects of concentration of acetic acid, mass ratio of CS to PVA, concentration of CS/PVA, distance between the capillary and collector, voltage and flow rate on the morphology and diameter of the electrospun nanofibers were investigated. The results indicated that the mass ratio of CS to PVA and the concentration of CS/PVA influenced the morphology and diameter of the electrospun nanofibers most, and the optimal electrospinning conditions were: the concentration of acetic acid was 90 wt%, the mass ratio of CS to PVA was 1:1,the concentration of CS/PVA was 8.0 wt%, the distance between the capillary and collector was 12 cm, the voltage was 24 kv and the flow rate was 0.1 mL/h.Secondly, air filtration properties of CS/PVA nanofibrous membranes were studied. The effects of thickness of nanofiberous membrane, fiber diameter, number of layers and air flow rate on the filtration properties of nanofibrous membranes were investigated. The results showed: with the increasing of the thickness of nanofiberous membrane, filtration efficiency and pressure drop increased on the exponential and linear function respectively, and the filtration efficiency and pressure drop were 98.68% and 813.30 Pa（10.8 m/min）respectively, when the thickness of nanofiberous membrane increased to 65.0 μm; for single layer of 65.0 μm nanofiberous membranes, with the decreasing of the fiber diameter, filtration efficiency and pressure drop increased simultaneously, and the optimal fiber diameter was 173 nm; multiple thin layers of nanofiberous membrane had better filtration properties than the single thick layer of nanofiberous membrane, compared to the single layer of 65.0 μm nanofiberous membrane, four layers of 16.25 μm nanofiberous membrane had the same filtration efficiency, but the pressure drop decreased about 200 Pa; for the single layer of 65.0 μm nanofiberous membrane, with the decreasing of air flow rate from 85 L/min to 30 L/min, the filtration efficiency of the nanofiberous membrane increased from 98.68% to 99.98%, and the pressure drop decreased from 813.30 Pa to 312.50 Pa.Lastly, CS/PVA/CaCO3 hybrid nanofibrous membranes were prepared by using a facile alternate socking process and a directly electrospinning CaCO3 precursor solution method. The effects of alternate cycles and concentration of CaCl2 on the crystal growth of CaCO3 were investigated respectively. The results showed: alternate socking process can quickly control to generate a large amount of CaCO3,calcite and vaterite with different diameters were generated after several cycles; electrospinning precursor solution method can facilely control to generate a single crystal of calcite. |
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