The Preparation Of Functional Nano Fiber Membranes And Their Applications To The Separation And Enrichment Of Heavy Metals In The Environment

Electrospinning is a technology for preparation of fibre materials with diameters in the scale of nanometer which exhibits high specific area. Therefore, electrospinning nanofiber membrane may have a great potential for the adsorption of metal ions. With electrospinning technology, we study two kinds of functionalized nanofibre membranes with applications of adsorption of heavy metals ions. The main works in thesis are described as the following:In part one, Cellulose acetate (CA)/Polyvinylpyrrolidone (PVP) nanofiber membranes were produced using the electrospinning technique. Subsequently, the membranes were treasted by water and alcoholic NaOH. Based on SEM studies, a number of grooves were found on the surface of washed fibers when the CA/PVP membrane was treated by ultrasonic wave in the water, this could result in larger specific surface area than before. And then the membranes were functionalized with thiol groups. The results of FTIR indicated that the thiol groups were successfully modified to the membranes. The thermogravimetric analysis (TGA) measurements showed the thermal stability of the membranes. The chelating property of the thiol-functionalized cellulose nanofiber membranes (TCM) was evaluated against Cu, Cd and Pb ions. The amounts of the metal ions adsorbed onto the TCM were influenced by the pH and the contact time. The Langmuir model was able to describe the adsorption isotherm results of the TCM for these ions better than the Freundlich mode. The maximum adsorption capacities of Pb, Cu, and Cd ions on TCM were estimated at30.96,19.63,34.70mg/g, respectively. The adsorption data of the three kinds of metal ions on the TCM were better described with the pseudo second order kinetic model. Lastly, the TCM could be facilely regenerated with a hydrochloric acid (HCl) aqueous solution and was almost maintained through three recycling processes of adsorption and desorption.In part two, nanofibre membranes from the composite of polyacrylonitrile (PAN)/PVP were prepared using electrospinning technique. After being treated with water to remove partially the PVP, the membranes were further functionalized with amido groups using triethylene diamine. Related materials were characterized using infrared and TGA. The adsorption capacity of the amido-functionalized nanofibre membranes (ACM) was evaluated against Cr (Ⅵ) ion. Adsorption conditions (acidity and contacting time) for Cr (Ⅵ) ion were optimized. Our results suggested that the adsorption behaviour of the selected metal ion could be described using Langmuir model. The maximum adsorption capacities of Cr (Ⅵ) ion on ACM were estimated at55.55mg/g. Their adsorption kinetics is in agreement with the model of pseudo-second order. The durability of the TCM was also evaluated by repetitive adsorption-desorption.