Preparation Of TiO₂/rGO 3D Framwork Material For Adsorption-photocatalytic Removal Of Micro-organic Contaminants In Water

Micro-organic contaminants（MCs）pollution in aquatic environments has become a global environmental problem since MCs were frequently detected from water sources in China even around the world.MCs can potentially and permanently harm the human body due to their complicated chemical structure,strong stability and difficult natural attenuation.Due to the low concentration and high mass transfer resistance,MCs are difficult to be removed by traditional processing techniques.Therefore,it is necessary to overcome the mass transfer resistance,improve the adsorption of MCs on the surface of the material,and develop photocatalytic materials with large specific surface area,strong adsorption-photocatalytic activity,and efficient removal of MCs in water.In this study,3D-TiO₂NWs/GO（3D-GNW）frame ultralight materials were prepared by one-step freeze-drying methods,and further high-temperature hydrogen reduction to prepare 3D-TiO₂NWs/rGO（3D-rGNW）,using the titanium dioxide nanowires（TiO₂NWs）with high length/diameter（L/D）ratio and graphene oxide（GO）ultra-thin nanosheets as precursor.XRD,Raman,FT-IR,FE-SEM,TEM,UV-Vis DRS,XPS and BET were used to characterize the phase composition,micro-morphology,light absorption performance and pore size distribution of the frame materials.The results show that TiO₂NWs is a key frame component for constructing a 3D network structure.GO nanosheets are interwoven with TiO₂NWs to form a three-dimensional frame material with low mass density and rich pores.After the high temperature hydrogen reduction,the 3D-rGNW three-dimensional frame structure still remains,with a small amount of Ti³⁺doping.The results of N₂ adsorption-desorption indicate that 3D-GNW is mainly mesoporous,and 3D-rGNW mesopores and macropores coexist.The BET specific surface area of both is significantly increased compared to TiO₂NWs.Taking methylene blue（MB）as the target pollutant,the effects of compounding ratio and freezing method on the adsorption-photocatalytic performance of 3D-GNW were studied under UV light.The results show that 2:1-TiO₂/GO can better display a randomly oriented interconnected network structure;3D-GNW prepared by liquid nitrogen rapid freezing shows the highest activity compared with refrigerator freezing and freeze dryer freezing.With low concentration of ethenzamide as the target degradation product,the adsorption-photocatalytic performance of 3D-rGNW on MCs was investigated under ultraviolet（UV,254nm）and vacuum ultraviolet（VUV,185nm）illumination.The results showed that the adsorption rate of 3D-rGNW to low concentration ethenzamide dark reaction reached 8.06%in 10 minutes,the removal rate reached 98.5%in 60 minutes under UV irradiation,the apparent rate constant of photocatalysis was 17.4 times that of 3D-GNW,and 2.2 times that of TiO₂NWs.The removal rate reached 96.8%when exposed to VUV light for only 3 minutes,which was significantly higher than 81.9%of TiO₂NWs alone and simple mixed samples.The corresponding photocatalytic apparent rate constant reached 0.285 min^-1.Repeated use three times under UV light,it still shows good adsorption-photocatalytic performance for low concentration ethenzamide.Based on the results of PL,EIS testing and active species capture experiments,the mechanism of 3D-rGNW framework material for adsorption-photocatalytic degradation of MCs in water was discussed:3D-rGNW framework material facilitates migration channels and rich pore structure,which promotes the vortex of MCs diffusion allows more MCs to be absorbed and concentrated into the 3D-rGNW’s internet-like structure.The refraction-reflection effect of the 3D network structure is conducive to the capture of light by the active site.Under UV light,the presence of Ti³⁺and oxygen vacancies reduces the energy required for 3D-rGNW light excitation.The chemical bonding of TiO₂NWs and rGO and the superior electron transport capability of rGO effectively promote the separation of e^--h⁺pairs.MCs are effectively decomposed under the combined action of h⁺,·OH,·O₂^-active species.