| With the rapid development of livestock and poultry industry in China,the residue of antibiotics in aquaculture wastewater has brought potential harm to human health and ecological environment.Traditional wastewater treatment methods cannot effectively remove antibiotics from wastewater.Visible-light photocatalytic technology has the characteristics of fast reaction rate,strong oxidation ability and no pollution,which has become an important direction of antibiotic waste water treatment technology research.Graphite phase carbon nitride(g-C3N4)has attracted extensive attention from researchers at home and abroad because of its high stability,suitable band structure,high catalytic activity,low preparation cost and so on.However,it also has the problems of high recombination rate of photogenerated electron hole and low quantum efficiency,which leads to lower photocatalytic activity,thus affects its application in the field of environment.In this paper,the applications of g-C3N4 catalysts under visible light irradiation were further studied,g-C3N4 catalysts and chlorine doped g-C3N4 catalysts were prepared through supramolecular self-assembly with post-heating treatment.The morphology,structure and optical properties of samples were characterized in detail by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),New high-resolution field-emission scanning electron microscopy(FESEM),UV-visible diffused reflectance spectrum(UV-vis),Photoluminescence spectrum(PL),and Thermal analysis(TGA).The photocatalytic activity and photodegradation mechanism of tetracycline hydrochloride by g-C3N4 catalysts in visible light were preliminary studied.(1)Using melamine and cyanuric acid as raw materials,g-C3N4 catalysts(CN-D,CN-H and CN-E)were successfully prepared through supramolecular self-assembly,which used dimethyl sulfoxide,water and ethanol as solvent respectively.The characterization results indicated that different solvents did not change the graphite phase structure of g-C3N4 catalysts.However,there were obvious differences in the morphology and optical properties of the synthesized g-C3N4 catalysts,due to the different solubility of melamine and cyanuric acid in the solvents of dimethylsulfoxide,water and ethanol.CN-D has higher visible light utilization,and its photodegradation rate of tetracycline hydrochloride is the best.(2)The effects of catalyst dosage,initial concentration,and initial pH on the photocatalytic degradation of tetracycline hydrochloride were investigated,using CN-D as a catalyst and tetracycline hydrochloride as simulated pollutant.The results showed that the degradation efficiency of tetracycline hydrochloric under visible light irradiation for 2 h could reach 80.54%when the dosage of CN-D catalyst was 1.0 g/L;the initial concentration of the tetracycline hydrochloride solution was 10 mg/L;and the initial pH was 7.The cycling experiments showed that the CN-D catalysts have good reusability.The free radical trapping experiments revealed that ·O2-and h+ are the main active species and ·OH is secondary active species in the photocatalytic degradation system of CN-D catalysts.(3)A series of Cl-doped CN-D catalysts(Cl-CN-D)were prepared through supramolecular self-assembly using melamine,cyanuric acid and ammonium chloride as raw materials and dimethyl sulfoxide as solvent.The characterization results indicated that the introduction of chlorine did not change the graphite phase structure of CN-D catalysts.However,it could narrow the band gap,broaden the light adsorption range and enhance the utilization of visible light.Photodegradation experiments showed that Cl-doped CN-D catalysts performed a higher photocatalytic activity than CN-D catalysts.The degradation rate of tetracycline hydrochloride could reach 90.42%under light irradiation for 2 h when the doping amount of chlorine was 15%.And the reaction rate constant of 15%-Cl-CN-D was 1.4 times that of CN-D. |
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