Adsorption Kinetics And Photocatalytic Activity Of Graphene Oxide-TiO₂ Composites For Dyes

The vigorous development of various industries in the country's chemical industry has brought a lot of dye pollution problems.The molecular structure of the dye contains unsaturated groups—N?N—,C=C,—N=O,etc.,with different chromaticity,polarity,and acidity and alkalinity.It is difficult to effectively destroy these conjugated structures by general methods.Photocatalytic oxidation technology has the advantages of high catalytic activity,low cost,no toxicity,no secondary pollution and complete mineralization.However,the photocatalytic degradation process firstly adsorbs organic pollutants to the surface of the photocatalyst to enrich the organic pollutants;then,under the light conditions,the hydroxyl radicals generated by TiO₂ are used to degrade organic pollutants into CO₂ and H₂O.Due to the strong hydrophilicity and low specific surface area of pure titanium dioxide due to the large amount of hydroxyl groups on the surface,the adsorption capacity of organic pollutants is extremely weak,which limits the photocatalytic degradation efficiency.Conventional photoreactors have complex structures,poor mass transfer effects,and difficult catalyst separation,while limiting photocatalytic efficiency.Therefore,the catalytic efficiency of the photocatalyst,the structural characteristics of the photoreactor,and the like seriously affect the photocatalytic efficiency.Modification of the catalyst can significantly improve the adsorption performance of TiO₂,separate photogenerated electrons and holes,and expand the range of visible light response,thereby improving the photocatalytic performance of TiO₂ composites and achieving efficient treatment of dye wastewater.A novel photocatalytic reactor capable of strengthening mass transfer and manufacturing a thin liquid film,a spinning disk reactor?SDR?,has wide application and good effect and can be used in a photocatalytic reaction.Under the centrifugal force of the turntable,the droplet becomes a thin liquid filament and a liquid film,which enhances the light transmittance and the dissolved oxygen amount,and has a strengthening effect on photocatalysis.The supported catalyst solves the problem of difficult separation and is sustainable.In this study,the graphene oxide-TiO₂ composite?GO-TiO₂?was successfully prepared by hydrolyzing butyl titanate in a graphene oxide dispersion solution,using Fourier transform infrared spectroscopy?FT-IR?and X-ray diffraction?XRD?.Scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,fully automated surface and pore size analyzer?BET?and UV-vis DRS were used to characterize the samples.The adsorption kinetics and photocatalytic properties of GO10-TiO₂ for methylene blue?MB?,methyl orange?MO?and rhodamine B?Rh B?dyes were studied.The results show that the TiO₂ particles are uniformly attached to the surface of the GO sheet;the adsorption process of GO10-TiO₂ on the three dyes is multi-layer adsorption,and the adsorption kinetics is in accordance with the pseudo-second-order kinetic model;the wastewater is treated with GO10-TiO₂ at 25°C.The adsorption of MB,MO and Rh B in the medium showed selective adsorption due to the difference in conjugate structure and polarity,and the adsorption capacities were 9.2,5.4 and 23.0 mg/g,respectively.The photocatalytic degradation of the three dye wastewaters was related to the adsorption performance.The higher the adsorption capacity,the higher the degradation efficiency.The degradation rates of MB,MO and Rh B were 89%,75%and 98%,respectively,after photocatalytic reaction for 60 min.Sol-gel method was used to prepare pure TiO₂ and GO-TiO₂ catalyst thin films,and 2 h was roasted at 450 degrees.XRD and SEM characterization of pure titanium dioxide and GO-TiO₂ dioxide catalyst films show that there are anatase and rutile mixed crystalline forms in both catalysts.There are many fine cracks on the surface of the films.The increase of cracks increases the specific surface area,while there are cracks on the surface of GO-TiO₂ film and a large number of black flocs.This substance is GO.Photocatalytic degradation of methylene blue wastewater by two supported catalyst films in SDR was studied.The results show that the degradation rate of methylene blue increases first and then decreases with the increase of flow rate and rotational speed.The rotating speed of 100rpm and flow rate of 40 L/h are the optimum experimental parameters for photocatalysis of rotating disc reactor.The photocatalytic degradation rate of methylene blue by GO-TiO₂film is 10%higher than that of TiO₂.