Fabrication Of PVDF-TiO₂ Composites By Electrospinning Technology And Their Adsorption-photocatalytic Performances

Titanium dioxide?TiO₂?polyphase photocatalysis in the removal of organic pollutants in water had been more and more widely studied.Compared with homogeneous catalytic oxidation processes?such as Fenton process,ozone de composition,etc.?,TiO₂ photocatalysis could be used at room temperature,atmospheric pressure and neutral p H without adding additional chemicals.In addition,titanium dioxide?TiO₂?photocatalyst was very stable,reusable and cheap,so it had broad application prospects.However,there were some problems in the application of titanium dioxide in photocatalysis,such as easy agglomeration and difficult recovery of nanoparticles,which maked the application of titanium dioxide severely challenged.By loading titanium dioxide nanoparticles,the dispersion degree and recovery efficiency could be effectively improved,thus improving the photocatalytic efficiency of TiO₂ and reducing the operating cost.In this experiment,poly?vinylidene fluoride??PVDF?was selected as the substrate material of photocatalyst TiO₂.PVDF nanofibers were prepared by electrospinning technology,and then TiO₂ was fixed on the surface of the substrate fibers in combination with the electrospraying technology.Thus PVDF-TiO₂ composite nanofibers with synergistic effects of adsorption and photocatalysis were prepared.In order to improve the adsorption performance of the substrate fibers,PVDF nanofibers with porous structure were obtained by blending the porous polyvinylpyrrolidone?PVP?with PVDF,and then soaking the PVDF/PVP blended fibers in anaqueous ethanol to selectively remove the PVP component.By means of scanning electron microscopy?SEM?,X-ray diffraction?XRD?,infrared spectroscopy?FT-IR?and water contact Angle?CA?,the structure,morphology and wettability of the porous nanofibers and composite nanofibers were tested.XRD and FT-IR characterization results showed that TiO₂ nanoparticles were successfully loaded on the surface of the substrate fibers,and the introduction of TiO₂ did not produce new chemical bonds.The SEM results showed that the porous substrate fibers were successfully prepared by the pore-making process.The surface of PVDF-TiO₂ composite nanofibers were layered with highly dispersed nanoparticles.Through the water contact angle test,it could be known that due to the porous structure of the nanofibers surface,the fiber could be wetted by water droplets and eventually became completely hydrophilic.The adsorption and photocatalytic degradation properties of PVDF-TiO₂ composite nanofibers were investigated using cationic dye methylene blue?MB?as the target pollutant.Adsorption experiments with MB as adsorbent showed that,by the using of polyvinylidene pyrrolidone?PVP?as pore-making agent to the nanofibers and with the mass ratio of PVDF: PVP of 1:1,the best adsorption capacity of the scaffolds was the value of 46.87 mg/g.And the photocatalytic degradation performance of the composite nanofibers were directly proportional to the embedded amounts of the nanoparticles.Moreover,the introduction of the porous and the embedding of the photocatalytic nanoparticles contributed the synergetic effects by improving the adsorption capacity to 85.70 mg/g within relative short period of time,and so the photocatalytic efficiency of titanium dioxide was enhanced and the energy requirement of photocatalysis was reduced to some extent.By fitting the curves of the two kinetic models,it could be seen that the adsorption behavior of PVDF-TiO₂ composite nanofibers to methylene blue belonged to pseudo-second order kinetic mode;the adsorption behavior of the composite nanofibers to methylene blue belonged to Langmuir adsorption isotherm model.And through fourth cycles of the adsorption and the photocatalytic experiments,the composite nanofibers showed relative excellent recycling performances?>89.5%?.In summary,we provided a simple preparation method for polymer-inorganic semiconductor photocatalysis to remove contaminants from water.