Electrospinning of PAN/DMF/H2O containing TiO2 and photocatalytic activity of their webs
Introduction
Photocatalysis is a decomposing process of organic substance under radiation with presence of photocatalyst. It is considered as clean process, which can be used for many applications including water and air purification. Among various potential metal oxides, TiO2 has been widely used as photocatalyst due to its chemical stability and availability in commercial [1]. In application, TiO2 particles are preferred to be immobilized on supporting materials to prevent particles agglomeration and make it easy to recover afterwards [2].
Electrospinning has been actively studied in many polymers such as polyethylene oxide, polybenzimidazole, polyacrylonitrile, and polyaniline just to name a few [3]. Recently, electrospinning of polymer solution containing photocatalyst has been employed as alternative approach to immobilize photocatalyst on nanofiber webs with goal to increase surface area for photocatalytic activity [4], [5], [6]. Nanofibers obtained from electrospinning are very small in diameter, which allows more chance for TiO2 particles to appear on fiber surface, i.e. better exposure to radiation. This may help increasing its photocatalytic activity. In addition, porous surface of supporting media may also assist photocatalytic activity such that organic molecules are first adsorbed onto porous surface, then migrated to photocatalyst, and degraded by photocatalysis under UV irradiation [7]. Porous structure on nanofibers surface was observed in electrospun web of PAN/DMF/H2O ternary system, which was explained due to bimodal decomposition phase separation during electrospinning [5].
In this paper, polyacrylonitrile was used as supporting material for photocatalyst TiO2 nanoparticles. Electrospinning of PAN/DMF/(H2O) solutions containing different amounts of TiO2, fiber features including porous structure on fibers surface, as well as photocatalytic activities of electrospun webs were investigated.
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Materials
Polyacrylonitrile (Mw. = 1.5x105 g/mol, d = 1.184 g/cm3), Titanium dioxide (anatase, ave. size 25 nm.) both purchased from Aldrich, and Dimethyl formamide (d = 133 g/cm3, RCI LabScan) were used as received. Methylene blue (Riedel-de-Haen) was used as a model pollutant.
Electrospinning of PAN/TiO2 webs
5% w/w. PAN/DMF solutions containing different amounts of TiO2 (0, 1, 2, and 3 wt.%) were prepared. As for example: to prepare 5% w/w. PAN/DMF/1 wt.% TiO2 solution, 0.5 g PAN was added into 9.5 g DMF, followed by 0.1 g TiO2 and stirred. For
PAN/TiO2 electrospun webs
SEM images of nanofibers webs obtained from PAN/DMF/0-3%wt.TiO2 solutions were shown in Fig. 1a and b (a0-d0). Averaged fiber sizes were in range of 170–220 nm., with tendency of increase with amount of TiO2. High magnification SEM (Fig. 1b, a0-d0) revealed rough fiber surface which was thought to be partly due to presence of TiO2 particles on the surface. Data from EDS analysis confirmed TiO2 on fiber surface. Electron scattering peak at 4.5 keV, corresponding to Ti, was observed in those
Conclusions
Electrospun PAN/TiO2 nanofiber webs were prepared from PAN/DMF and PAN/DMF/H2O solutions containing different amounts of TiO2 (0 to 3 wt.%). Small amount of non-solvent water (3 and 5%w/w.) was introduced into PAN/DMF/H2O system to induce formation of porous structure on nanofibers surface. The obtained PAN/TiO2 webs possessed nanofibers with rough surface and fiber diameters in range of 170–430 nm. Porous structure on fibers surface was not clearly observed, which may be because amount of water
Acknowledgements
This work was supported by the National Metal and Materials Technology Center (grant number: MT-B-52-POL-07-435-I).
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