Supported TiO₂ Composite Photocatalyst For The Degradation Of Dye Wastewater

Organic pollutants have serious implications for aquatic organisms and human beings.Effective photocatalytic degradation of organic substances has been extensively studied,due to its low cost,non-toxicity,high efficiency,stability,and no secondary environmental pollution.Titanium dioxide is the most popular photocatalyst material due to its strong oxidizing ability,chemical stability,and nontoxicity.Drawbacks of titanium dioxide include the high recombination rate of photogenerated electron-hole pairs,the low utilization of solar energy,and poor recyclability for reuse.In this study,the titanium dioxide,which was used for photocatalytic degradation of organic dyes,was served as main material to improve the catalytic performance via modification.The polyvinyl alcohol/reduced graphene oxide/titanium dioxide/gold（PVA/RGO/Ti O₂/Au）composite,reducedgrapheneoxide/titanium dioxide/molybdenum disulfide（RGO/Ti O₂/Mo S₂）composite,and polyvinyl alcohol/titanium dioxide/reduced graphene oxide/gold（PVA/Ti O₂/Mo S₂/Au）composite were successfully synthesized,respectively.1.The polyvinyl alcohol/reduced graphene oxide/titanium dioxide/gold（PVA/RGO/Ti O₂/Au）composite was successfully synthesized with PVA as the carrier via a mild,low-temperature wet chemical method and characterized by fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,UV-vis diffuse reflectance spectroscopy（UV-vis DRS）,Photoluminescence（PL）,and Brunauer-Emmett-Teller（BET）.PVA/RGO/TiO₂/Au composite had a uniform,hierarchically network structure with many pores,which showed great absorbance in the visible light range and effectively inhibited the recombination of photogenerated electron-hole pairs.The synthesized composite showed a high photocatalytic degradation activity for rhodamine B（Rh B）under high pressure sodium lamp irradiation.The photocatalytic degradation activity was closely related to the catalyst concentration,the initial Rh B concentration,the p H,and the H₂O₂concentration.The composite remained at nearly 94%of the initial photocatalytic degradation activity after five cycles.2.The reduced graphene oxide/titanium dioxide/molybdenum disulfide（RGO/Ti O₂/Mo S₂）composite was successfully synthesized via multi-step assembly methods,including sol-gel and physical vapor deposition（PVD）methods.The composite had a unique three dimensional（3D）sandwich network structure,and the abundant oxygen-containing functional groups,and a large specific surface area of255.441 m²/g,resulting in great absorption capacity.The optical and electrical properties of composite indicated a great absorbance in the visible light range and fast transfer rate of photogenerated electron-hole pairs,resulting in excellent photocatalytic performance.Under the cooperative action of adsorption and photocatalysis,the RGO aerogel/Ti O₂/Mo S₂showed a high removal efficiency of the cationic dyes.The removal activity was closely related to environmental conditions,such as the initial concentration and p H value.X-ray photoelectron spectroscopy（XPS）,and Fourier transform infrared spectroscopy（FTIR）demonstrated the formation of Ti-O-C bonds in this structure.Moreover,the Electron paramagnetic resonance（EPR）spectra analysis and the results of reactive species scavenging experiments confirmed that superoxide radicals（·O₂^-）,holes（h⁺）,and hydroxyl radicals（·OH）were involved in the photocatalytic degradation of organic dyes.3.The polyvinyl alcohol/titanium dioxide/reduced graphene oxide/gold（PVA/Ti O₂/Mo S₂/Au）composite was prepared via hydrothermal method.The successful preparation of composite was demonstrated via XRD,SEM,TEM and BET analysis.In the photocatalytic degradation reaction of Rh B,PVA/Ti O₂/Mo S₂/Au showed the great photocatalytic performance.Photocatalytic performance was closely related to environmental conditions such as initial dye concentration and p H.In the cycle test,PVA/TiO₂/MoS₂/Au had excellent stability and was promising in practical applications.