Preparation Of RGO/TiO₂ Composites Materials For Photocatalytic Degradation Of 4-Aminophenol

Photocatalyst TiO2,for its perfect photocatalytic activity, chemical stability and no secondary pollution, make it become the best photocatalytic materials, but TiO2 as a wide band gap semiconductor which have photo-generated electrons and holes compound too fast, low photocatalytic activity under visible light, inadequate surface area and small in photocatalytic degradation process. The new two-dimensional carbon materials graphene have became extremely effective method through the preparation of graphene-based composite oxide to improve the photocatalytic activity. In the paper, the graphene oxide(GO) were prepared by an improved low-temperature oxidation Hummers method, the reduced graphene oxide(RGO) was synthesized by the methods of UV/thermal reduction process, the RGO/TiO2 composite photocatalyst materials were prepared through sol-gel-calcination method by using RGO and tetra-n-butyl titanate as precursors. The photocatalytic activity of RGO/TiO2 were studied by using 4-aminophenol(PAP) as modeled wastewater and ultraviolet light as light source, to probe the influence factors on the degradation of PAP and its mechanism using different catalysts, value of pH, graphene loaded and its dosaged, initial concentration of PAP.(1) The graphene oxide(GO) were prepared by an improved low-temperature oxidation Hummers method in the help of ultrasonic using flake graphite as raw materials. These complexes were characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), ultraviolet-visible spectroscopy(UV-Vis). The results show that, GO were prepared by a low temperature condition than the high temperature condition of GO-H prepared have more well-ordered layered structure, such as the surface-OH,-COOH,-C=O,-COC- containing oxygen functional groups, expand the interlayer spacing of GO. The graphite intercalate slowing and uniform, make the grain size thinning at low temperatures, drop reaction conditions. The presence of oxygen-containing groups improve aqueous dispersion of GO at the same time.(2) The reduction graphene oxide(RGO) were prepared by more green method of ultrasound assisted-UV coupled thermal reduction process using GO as probe matter. The RGO/TiO2 composite photocatalyst materials using modified sol-gel-450℃ high temperature heating process, changing the content of the RGO in raw materials, preparation of graphene controlled loading of 1%, 1.5%, 2%, 3% through tetra-n-butyl titanate and RGO as precursor, and RGO/TiO2 composites materials were characterized by XRD, FT-IR, SEM,UV-Vis. The results show that, the GO of containing oxygen functional groups are removed using the method of ultrasound-ultraviolet excitation and coupled high-temperature thermal reduction process, and restore six-carbon ring structure of the RGO. The RGO have fewer layers and not give uniformly dispersed in water and no stable ability, standing precipitation will occur. The composite materials crystallized, TiO2 particle size of 20~40nm crystal and anatase structure appears, distributting and anchoring evenly in the sheet of RGO, graphene oxide surface groups are more removed, the ring structure of graphene has been further repaired at 450℃ high temperature.(3) The photocatalytic activity of RGO/TiO2 were studied by using 4-aminophenol(PAP) as modeled wastewater and ultraviolet light as light source, to probe the influence factors on the degradation of PAP. The results show that, that composites RGO/TiO2 exhibited significantly higher photocatalytic activity than GO/TiO2 and pure TiO2 on degradation of PAP. The photocatalytic activity of composites RGO/TiO2 depended on loading rate of RGO and pH value: after 12 h, the degradation of PAP reached 95.75% when the dosage of RGO/TiO2 was 1.2g/L, the content of RGO was 1.5%, pH was 3 and the initial concentration of PAP was 50mg/L. The degradation rate of PAP increased first and then decreased with increasing the dosage of RGO/TiO2. photocatalytic effect of PAP is poor in neutral and alkaline condition, the removal effect of PAP was remarkable under low pH conditions and RGO doped 1.5%.(4) The composites RGO/TiO2 photocatalytic process analysis on degradation of PAP, after 8h photocatalytic degradation, CODcr basically dropped 50 mg/L or less. Photocatalytic process on degradation of PAP in line with the proposed level kinetic model, the correlation coefficient fit more than 0.97; the preliminary view that the composites RGO/TiO2 on the degradation mechanism of PAP may be as follows, after doped of RGO, the specific surface area of composite nanomaterials and the amount of the PAP adsorbed increases, generating of H2O2, ?OH attack PAP molecules adsorbed, a series of redox reactions happened which produce a series of free-radical reaction to produce low molecular weight organic acids and alcohols, such as pyrogallol, benzoquinone, oxalate and easily oxidizable produces, eventually degrade to CO2 and H2 O.