| Dye wastewater is one of the most difficult to deal with industrial wastewater due to its large quantity,complicated components,high toxicity,high chromacity and COD Cr value,which He has become bottlenecks in printing and dyeing industry. Since the Thirteenth five-year plan, our country is in the adjustment of industrial structure, gradually banning a number of dyestuff production enterprise. However, A large amount of dye wastewater without dffective processing has been discharged into water body, which reduce the dissolved oxygen and the self-cleaning capacity of body water and is harmful to the growth of hydrobiont; meanwhile, damage aquatic ecosystems and soil ecosystem, hinder China’s economic development and endanger people’s health. Effective treatment methods to dye wastewater are an important guarantee of economic and social sustainable development.At present,common treatments for dyestuff wastewater mainly consist of physical method, chemical method,biological method and some combination technology. Whereas,along with the increasingly difficult of dyestuff wastewater treatment and the improved requirements of environmental protection,the traditional common processing method with High energy consumption and low efficiency is difficult to achieve the emission standards.Semiconductor photocatalytic degradation technolog because of its high efficiency,no pollution and low price is studied intensively. For the reason that, samples, as catalysis with Zinc oxide(Zn O), bismuth sulfide(Bi2S3) and graphene phase carbonized nitrogen(g-C3N4) as the catalyst, were used to degrade simulation dye effluents, such as solutions of Rh B,MO. A variety of methods have been used to enhance the catalytic activity under the visible light to study the semiconductor photocatalysts degradation of dye wastewater under visible light, the work and conclusions are included as follows:(1) Samarium-doped Zn O Nanoparticles were synthesized via a facile and surfactant-free solvothernal method after calcined 3h at 400 ℃. The prepared nanostructures were characterized by UV-vis spectrophotometer, scanning electron microscopy(SEM), energy dispersive spectrum analysis(EDX) and Fourier transform infrared spectroscopy(FTIR).The SEM images show that the synthesized Zn O nanoparticles are regular hexagonal columnar body. And the morphology of the nanostructures is not changed after doped Sm,while the crystal volume of Zn O-Sm nanoparticles become smaller. The EDX spectrum depict that Sm ions are successfully doped into Zn O. The photocatalytic studies show that the Zn O-Sm(2.0at.%) photocatalytic degradation of Rh B enhanced approximately 30% under visible light irradiation compared with the pure Zn O. And in order to obtain the best photocatalytic effect, the optimal experimental conditions were explored. As such, Zn O-Sm nanostructures were indicated great potential for practical applications in wastewater treatment.(2) Visible light responsive heterojunctions of graphitic carbon nitride(g-C3N4) and Bi2S3 were successfully designed and constructed by a simple solvothermal process. The as-prepared samples were characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), transmission electron microscopy(TEM), high resolution transmission electron microscopy(HRTEM) and UV-vis diffuse reflectance spectroscopy(DRS). Under visible light irradiation, the as-prepared g-C3N4/Bi2S3 photocatalysts exhibit highly enhanced photochemical efficiency in the degradation of methyl o range(MO) compared with pure g-C3N4 and Bi2S3. On the basis of the calculated energy bands, the excellent enhancement is attributed to the efficient separation of photoinduced electron-hole pairs. In addition, a detailed degradation pathway of MO degradati on by g-C3N4/Bi2S3 composites is proposed to further elucidate the inner photodegradation mechanism. This research may provide a cost-effective and easy-scaling up approach to develop visible-light-driven photocatalysts, which could be applied in wastewate r treatment. |
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