Preparation, Characterization And Photocatalytic Performance On Dye Wastewater Of Modification Nanometer Titanium Dioxide

Dye wastewater is the main source of industrial effluent.It is recognized as a kind of unmanageable industrial effluent,which can be ascribed to its large quantum,high concentration,complex component,dark chroma,high salinity,strong toxicity,and difficulty by biochemical degradation.Currently,more and more researchers become interested in this issue.Photocatalysis-oxidation is a senior oxidation technology with high efficiency.The commonly used catalyst in heterogeneous photocatalysis is nanometer titanium dioxide, which can be used for the treatment of dye wastewater.But the photocatalysis based on nanometer titanium dioxide usually proceed in liquid-solid phase and gas-solid phase. So the catalyst is easy to run off and hard to recycle.Load of titanium dioxide is an efficient approach for the separation and recycle of catalyst.It can also solve the problem of gas carry secretly.The loading technique for nanometer titanium dioxide mainly includes the selection of catalyst carrier and the loading technology.Because titanium dioxide can only adsorb the ultraviolet light,the adsorption rate for visible light or sun's rays is quite low.The key for the improvement of light using efficiency lies in the breakthrough of the forbidden band width of catalyst and the expansion of the response spectrum to visible light.The photosensitization of titanium dioxide is an important means to extend the excitation wavelength.Titanate whisker,attapulgite clay,cenosphere and float beads were selected as the carrier,and anatase nanometer titanium dioxide as the substrate in our research.The high mechanism performance,thermal stability,small size effect,ultraviolet response and high adsorption properties of titanium dioxide was integrated with the ultraviolet response of heteropoly acid and the Q band adsorption behavior of phthalocyanine compound.Heteropoly acid or phthalocyanine compound was decorated on the surface of titanium dioxide,and the compound photocatalyst was prepared through loading and photosensitive modification of titanium dioxide.The adsorption range and application field of the novel material were extended because the light response area of novel material had red shift.The photocatalysis performence was investigated with different dyes as the substrates in the photochemical appearance.The main conclusions included the following items: (1)Study on solid-supported of nanometer titanium dioxideWith potassium titanate(â…£)as carder,TiO₂/potassium titanate photocatalyst was prepared with sol-gel method.With rhodamine B as substrate,the photocatalytic performance of TiO₂/potassium titanate was investigated under ultraviolet illumination. The product was characterized by X-ray diffraction and SEM.From the EDS,the main energy spectrum included Ti,O and K peaks in potassium titanate whisker.The Ti and O peaks stayed after the whisker was covered by TiO₂.The disappearance of K peak indicated that the surface of potassium titanate whisker had already covered by TiO₂.As shown in XRD,the diffraction peak corresponded to the characteristic peak of anatase TiO₂.Under irradiation of ultraviolet light,when the concentration of rhodamine B was 8 mg·L^-1,0.01 g·L^-1of TiO₂/potassium titanate was added.The decolorization rate for rhodamine B was over 95%in 160 min,which was 0.50 times higher than that with pure TiO₂.With attapulgite clay was carrier,TiO₂/attapulgite clay photocatalyst was prepared by sol-gel method.With methylene blue as substrate,the photocatalysis performance of TiO₂/attapulgite clay was investigated under ultraviolet illumination.Results from X-ray diffraction indicated that the diffraction peaks on its surface corresponded to the characteristic peaks of TiO₂.As shown in Energy Dispersive Spectroscopy(EDS),A1, Mg,Fe,K and Si peaks generated by attapulgite clay disappeared or weaken to some extent after loading process.Ti and O peaks were the main peaks,which indicated that attapulgite clay was covered well by TiO₂.Under irradiation of ultraviolet light,the decolorization rate of TiO₂/attapulgite clay for methylene blue was more than 90%in 30 min.With cenosphere as carrier,TiO₂/cenosphere photocatalyst was prepared by sol-gel method.The photocatalysis performance was studied by degradation of malachite green under ultraviolet illumination.The cenosphere loaded by titanium dioxide had strong ultraviolet response and excellent photocatalysis effect for ultraviolet light.Under the experimental conditions,the decolorization rate for malachite green was over 70%.Above experiments showed it was feasible with potassium titanate whisker, attapulgite clay or cenosphere as the photocatalyst carrier.(2)Study on visible light photosensitization of titanium dioxideWith potassium titanate(â…¥)whisker as carrier,and silicotungstic acid (H₄SiW₁₂O₄₀)as modified reagent,the compound photocatalyst H₄SiW₁₂O₄₀/TiO₂/K₂Ti₆O₁₃was prepared by sol-gel-dipping method.UV-vis spectra showed that the compound photocatalyst possessed stronger light response and higher photocatalysis activity.Under the experimental conditions,the decolorization rate for malachite green reached over 80%.With natrium titanate(â…¢)whisker(Na₂Ti₃O₇)as carrier and phosphotungstic acid (H₃PW₁₂O₄₀)as modified reagent,the compound photocatalyst H₃PW₁₂O₄₀/TiO₂/Na₂Ti₃O₇ was prepared by sol-gel-dipping method.The XRD results indicated that the product was well covered by anatase TiO₂ and phosphotungstic acid was Keggin structure.UV-vis spectra showed its light response was enhanced. Compared with TiO₂/Na₂Ti₃O₇,the decolorization rate increased by 18.3%for 10 min and 33.4%for 50 min with H₃PW₁₂O₄₀/TiO₂/Na₂Ti₃O₇ as photocatalyst.With float beads as carrier and phosphotungstic acid as modified reagent,the compound photocatalyst H₃PW₁₂O₄₀/TiO₂/float beads was prepared by sol-gel-dipping method.The prepared compound photocatalyst had stronger light response and higher photocatalysis activity for congo red degradation.With congo red as substrate,the degradation rate reached 90%after 70 min.(3)Study on ultraviolet light photosensitization of titanium dioxideWith potassium titanate(â…£)whisker as carder and cobalt sulfophthalocyanine as modified reagent,the compound photocatalyst cobalt sulfophalocyanine/titanium dioxide/potassium titanate(â…£)(CoPcS/TiO₂/K₂Ti₄O₉)was prepared by sol-gel-dipping method.The results indicated that the adsorption obtained by baking at 423K had obvious red shift,and adsorption between 600 and 680 nm was especially strong.The XRD results showed that the titanium dioxide was still anatase type.Under the visible light irradiation,the decolorization rate of X-3B reached 85%in 5 h.Compared with TiO₂/K₂Ti₄O₉,the decolorization rate of substrate was remarkably enhanced with CoPcS/TiO₂/K₂Ti₄O₉ as photocatalyst.With Na₂Ti₃O₇ whisker as carrier and tri-CoSPc as modified reagent,the compound photocatalyst tri-CoSPc/TiO₂/Na₂Ti₃O₇ was prepared by sol-gel-dipping method.UV-vis spectra indicated that the adsorption spectra of tri-CoSPc/TiO₂/Na₂Ti₃O₇ had red shift,and the light response area had extended to visible light(above 400 nm).There existed especially strong adsorption between 600 and 700 nm.With malachite green as the simulate contamination and tri-CoSPc/TiO₂/Na₂Ti₃O₇ as photocatalyst,the decolorization rate of malachite green reached 42.9%in 1 h and 90.3%in 6 h.The results indicated that titanate whisker,attapulgite clay,cenosphere and float beads could be used as the carrier for photocatalysts.Sol-gel method was developed to prepare loaded photocatalyst and sol-gel-dipping method was established to prepare photosensitive compound photocatalyst.The loaded photocatalyst and photosensitive compound photocatalyst based on titanium dioxide were effective for the treatment of various dye wastewater.