Preparation Of Alginate - Based Composite Nanofibers By Electrospinning And Their Properties

Sodium alginate (SA) is a naturally negatively charged linear polyelectrolyte. Its molecular chain contains lots of hydroxyl and carboxyl groups, which can react with heavy metal ions to form metal complex by sodium ion-exchange. Thus, it can be used as adsorbent for the removal of heavy metal ions from waste water.In this paper, the electrospinning technique was used to prepare Sodium alginate/Polyethylene oxide/Polyvinyl alcohol(SA/PEO/PVA) composite nanofiber membrane, and then TiO2 and CNTs-COOH nanoparticles were added into SA/PEO/PVA solution to make SA/PEO/PVA/TiO2 and SA/PEO/PVA/CNTs-COOH composite nanofiber membrane. The heavy metals ions adsorption performance was evaluated. The main work of this thesis includes the following three parts:(1) SA/PEO/PVA composite nanofiber was prepared by electrospinning of SA/PEO/PVA solution, followed by CaCl2:treatment. The surface morphology and properties of the SA/PEO/PVA nanofiber membrane were examined with scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), etc. According to the results, the optimal electrospinning parameters of fabricating SA/PEO/PVA electrospun membrane are:SA content 2.0wt%, feed rate 1.5mL/h, applied voltage 16kV, collection distance 20cm. The diameter of the SA/PEO/PVA nanofiber membrane is 329.68nm.(2) TiO2 and CNTs-COOH nanoparticles were dispersed homogeneously in the SA/PEO/PVA solution to prepare spinning solution. SA/PEO/PVA/TiO2 and SA/PEO/PVA/CNTs-COOH composite nanofiber was prepared under the optimal electrospinning parameters as previously determined. The diameter of SA/PEO/PVA/ TiO2 and SA/PEO/PVA/CNTs-COOH composite nanofiber obtained is lower than that of SA/PEO/PVA nanofibers. The electrospun nanofiber membrane were examined with scanning electron microscopy(SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric Analysis(TG), X-ray diffraction(XRD) etc.(3) The metal ions adsorption performance of the SA/PEO/PVA, SA/PEO/PVA/TiO2 and SA/PEO/PVA/CNTs-COOH composite nanofiber membrane was evaluated by Cu2+, Pb2+ and Cr6+ adsorption. The effect of adsorption conditions, such as initial ion concentration, pH value, contact time and temperature on the adsorption capacity were investigated. The results suggested that the adsorption behavior of Cu2+, Pb2+ and Cr6+ could be described using Freundlich model. Their adsorption kinetics is in agreement with the model of pseudo-second order. The durability of the SA/PEO/PVA/TiO; and SA/PEO/PVA/CNTs-COOH composite nanofiber membrane was also evaluated by repetitive adsorption-desorption.