| Due to its low cost, simple, high-efficiency, stability and renewability, adsorption has been one of the most processes for waste water treatment. Moreover, Photocatalysis could degraded organic pollutants into non-toxic inorganic molecule, such as H2 O and CO2 and so on, which has been the most potential environmentally technology. In this paper, two series of TiO2-based, five series of g-C3N4-based and two series of NiObased composited materials were obtained; The structure, surface morphology and chemical composition were characterized by Fourier-transform infrared spectroscopy（FT-IR）, UV-visible spectrum（UV-vis）, UV-vis diffuse reflectance spectroscopy（DRS）, X-ray diffractometer（XRD）, raman, scanning electron microscopy（SEM）, energy dispersive X-ray spectrometer（EDS）, transmission electron microscopy（TEM）, selected area electron diffraction（SAED） and X-ray photoelectron spectroscopy（XPS）; The treatment for organic wastewater were investigated. The main researches as follows: 1. Preparation of TiO2-based composited material and its visible-light photocatalytic activity research（1） A series of graphene oxide（GO） with different oxidation degree were prepared by changing the oxidation time in Hummers method, and the effect of different oxidation on the photocatalytic activity of TiO2-graphene photocatalysts（TGPPC） was studied. The degradation efficiency of MB over TGPPC could be obtained 98.8 % at a GO content of 20% and a time of 100 min. Photocatalytic degradation behavior of MB was investigated by the pseudo-first-order kinetics; and the photocatalytic degradation mechanism was proposed. The obtained results indicate that the prepared TGPPC has a potential application for the industrial effluents treatment containing MB.（2） A series Ag-AgBr/TiO2-graphene（AATG） photocatalysts were prepared by the deposition-precipitation method combining a subsequent calcination process. XRD and XPS results show Ag0 is generated from Ag+ under visible light irradiation. Degradation of polyacrylamide（PAM） was chosen to evaluate photocatalytic activity using AATG composite as photocatalysts. The conditions such as mass ratio of TiO2/graphene, catalyst dose, pH and contact time, were investigated for the degradation of PAM. Possible pathway and mechanism were proposed for photocatalytic degradation of PAM over AATG composite photocatalyst under visible light irradiation. The prepared AATG composite photocatalyst can be separated from system effectively and easily; and exhibits significant photocatalytic activity after five successive recycles. 2. Preparation of g-C3N4-based composited material and its visible-light photocatalytic activity research（1） The porous g-C3N4（PGCN） was prepared by pyrolysis of urea and dicyandiamide in N2 atmosphere. Porous structure of g-C3N4 increased BET special surface area. In addition, La-doping was used to improve the photocatalytic activity further. From the TEM morphology, the porous structure of g-C3N4 could be successfully controlled; from BET results, BET specific surface area of porous g-C3N4（PGCN） sample increases with the increasing of urea mass ratio. Compared with PGCN material（PGCN-50）, PGCN/La sample（PGCN-50/La-5） could exhibit an enhanced photocatalytic activity and has the best degradation efficiency of 98.6 % within 50 min under visible light irradiation. Photocatalytic reaction follows the first-order model kinetics; and PGCN-50/La-5 photocatalyst shows the largest reaction rate among all samples which is nearly 2.96 times higher than that of pure PGCN-50.（2） W-doped g-C3N4（PGCN） was selected to prepare W/PGCN photocatalyst, which can improve its visible-light absorption range and reduce the band gap. From XRD and XPS results, it can be inferred that the element W（as W6+） has been doped into the g-C3N4 interior of the W-5/PGCN-50 samples. The existence of appropriate amount of H2O2 could increase the rate of hydroxyl generation. Among all prepared samples, W-5/PGCN-50 exhibited the best photocatalytic activity and the degradation efficiency of MO achieves 99.6% within 60 min under visible light.（3） A coupled system for the photodegradation of Rhodamine B dye was realized using Bi2S3/g-C3N4 composite as a photocatalyst under visible light irradiation. The Bi2S3/g-C3N4 composite was prepared by a hydrothermal method. Compared with pure g-C3N4, Bi2S3/g-C3N4 sample exhibits an enhanced photocatalytic activity and the best photocatalytic efficiency is 3.68 times more than that of pure g-C3N4. The obtained results indicate that coupled system of Bi2S3 and g-C3N4 could overcome the drawback of low photocatalytic efficiency brought by electron-hole recombination and narrow photoresponse range. On the basis of the corresponding energy band positions, the mechanism of photocatalytic activity enhancement was proposed.（4） Single layer g-C3N4（SL g-C3N4） was fabricated by an ultrasonic exfoliation of bulk g-C3N4, the structure modification of g-C3N4 was realized. Two series of CdS/SL g-C3N4 and CdS/g-C3N4 photocatalysts with different Cd S content were prepared by hydrothermal process. The photoelectrochemical behaviors and photocatalytic activity of prepared photocatalysts were investigated. With the optimum CdS content of 33.3% and reaction time of 120 min, the degradation efficiency of Rhodamine B（RhB） achieves 99.55% under visible light irradiation.（5） ZnO is modified by Ag2 O and then supported by porous g-C3N4（pg-C3N4） to obtain the ternary combined ZnO-Ag2O/pg-C3N4 composite photocatalyst. From the DRS and PL optical property test, it can be obtained that ZnO-Ag2O/pg-C3N4 presents relative narrow band gap and higher separation rate of photoinduced charge carriers in the ternary combined system, which are favorable for the photocatalytic activity enhancement under visible light irradiation. Compared with ZnO, porous g-C3N4, Ag2 O and Zn O-Ag2 O, ZnO-Ag2O/pg-C3N4 presents the highest degradation efficiency（97.4 %） for antibiotic ciprofloxacin（CIP） within 48 min. Furthermore, porous g-C3N4 as a visible-light-driven photocatalyst used as supporter in the combined system not only improves the degradation efficiency, but also speeds up the reaction rate. 3. Preparation of NiO-based composited material and its adsorption/ photocatalytic performance research（1） A series of NiO/graphene nanosheets adsorbents（NGNS） were synthesized by a facile hydrothermal method. The NGNS was applied to deal with wastewater solution containing Congo red（CR）, and adsorption efficiency of NGNS-5 sample with graphene content of 2.64% attained 99.56%. The adsorption kinetic and isotherm of NGNS-5 towards CR were investigated. The results indicated that pseudo second-order kinetic model and the equilibrium data were well fitted by Redlich-Peterson model. The adsorbent can be separated from system effectively and easily. The prepared NGNS has potential application for the wastewater treatment containing CR azo-dye.（2） Nickel oxide/graphene oxide（NiO/GO） nanocomposite was prepared by a hydrothermal method combining a subsequent calcination process. Adsorption and photocatalytic performance was tested by the removal of aromatic heterocyclic dye methylene blue（MB） from aqueous solution. The effects of NiO/GO nanocomposite dose, p H, and contact time on the removal efficiency of MB were also investigated. Compared in the dark, NiO/GO nanocomposite shows a faster and higher removal efficiency by the photodegradation and adsorption under visible light irradiation. A remarkable removal efficiency of MB achieved 97.54% by NiO/GO nanocomposite after 120 min. |
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