The Preparation Of Amino Polymer Nanofibrous Materials By Electrospinning Technique And Their Application In Water Treatment

Electrospinning is a process of injecting and stretching a polymer solution or melt into nanofibers under electrostatic force, which is suitable for a variety of polymers. The nanofibers produced by electrospinning show very high specific surface areas and numerous pores across the assembled nanofiber net, which make electrospun materials quite suitable for some physical and chemical activities such as catalysis, adsorption and filtration. Amino polymers have various desirable characteristics such as hydrophilicity, high cationic charge density, N nucleophilic substitution, coordinating with metal ions. These features means that amino polymers are very favorable for removing various pollutants in wastewater. In this study, amino nanofibrous materials were fabricated through electrospinning technique and then applied in the water treatment. The main research are listed in the following:The water-soluble branched polyethylenimine（b-PEI） was modified with glycidyl methacrylate（GMA） via a ring-opening reaction. The modified PEI, so-called methacrylated polyethylenimine（m-PEI） with good water resistance was then blended with polyvinylidene fluoride（PVDF） and electrospun into m-PEI/PVDF nanofibrous mat. The characterizations by microwave digestion, FT-IR, TGA indicated that the water-insoluble m-PEI was prepared successfully. XPS and SEM characterization showed that the m-PEI/PVDF electrospun mat consisted of numerous nanofibers and a large number of pores across the fiber net, and hydrophilic m-PEI component was migrated to the surface after water immersion.The m-PEI/PVDF electrospun nanofibrous mat was applied to the adsorption of anionic dye-methyl orange（MO）. The maximum adsorption capacity reached 633.3 mg g^-1 when the initial MO concentration was 1 g L^-1, which is much higher than those reported. The adsorption behavior was influenced by the temperature, initial MO concentration, and pH of the solution. The adsorption kinetics suggested that the adsorption process followed the pseudo second-order kinetic model and was affected by film diffusion and intraparticle diffusion at least. The calculation of activation energy and the better fitting of Langmuir isotherm model indicated that the adsorption was a single layer physical adsorption process. What’s more, the adsorbent was well regenerated and showed good recyclability after immersion in a basic solution.Apart from organic pollutants, the inorganic pollutants such as heavy metal ions was also widely exists in waste water. Hence, the m-PEI/PVDF nanofibrous mat was applied to the adsorption of two typical heavy metal ions-chromate and arsenate. When the intial conetration of Cr（VI） and As（V） were 200 mg L^-1 and 400 mg L^-1, the maximum adsorption capacity f Cr（VI） and As（V） reached 109.1 mg g^-1 and 230.7 mg g^-1, respectively. The adsorption kinetics of Cr（VI） followed with the pseudo-first order kinetics model while the adsorption kinetics of As（V） was better fitted pseudo-second order kinetic model. The adsorption isotherms of Cr（VI） and As（V） were in accordance with the Langmuir isotherm model appropriately. Coexisting ions led to lower adsorption capacity and adsorption rate. Furthermore, the m-PEI / PVDF nanofibrous mat can still remove remove 85% of chromate and 98% of arsenate even at sub-ppm level, the strong affinity for Cr（VI） and As（V） indicated that the m-PEI/PVDF nanofibrous mat could be a promising candidate for drinking water purification.Aminated polyacrylonitrile（APAN） was synthesized through reaction with ethylene diamine（EDA） and PVDF-g-PAAc was synthesized by pre-irradiation induced graft polymerization, then APAN/ PVDF-g-PAAc nanofibrous mat was fabricated by two-nozzle eletrospinning technique. 1HNMR, XPS, FT-IR characterizations demonstrated the successful preparation of APAN. SEM images showed APAN / PVDF-g-PAAc electrospun mat consist of nano-scale fibers, which had better hydrophilicity than unmodified APAN / PVDF nanofibrous mat. Cross flow filtration results showed that APAN / PVDF-g-PAAc nanofibrous mat had significantly higher oil/water separation efficiency than the PAN / PVDF nanofibrous mat.