光催化材料CdS/TiO_(2)的制备及其光催化还原U(Ⅵ)性能研究

Preparation of CdS/TiO_(2) Photocatalytic Material and Its Photocatalytic Reduction of U(Ⅵ)

为探讨光催化还原技术在含铀废水中对U(Ⅵ)的还原性能,本文采用分步沉淀法制备了CdS/TiO_(2)复合纳米粒子,利用SEM、XRD、DRS等手段对其进行表征,并通过光催化还原U(Ⅵ)试验考察了材料的光催化还原活性。结果表明,CdS/TiO_(2)复合纳米粒子是由锐钛矿型、金红石型二氧化钛和立方晶型硫化镉组成的光催化材料,其颗粒大小为30~50 nm;与TiO_(2)相比,CdS/TiO_(2)复合纳米粒子的吸收光谱发生了明显的红移。CdS/TiO_(2)复合纳米粒子表现出较好的光催化还原U(Ⅵ)活性,在模拟废水pH=6.0、材料用量1.0 g/L时,对U(Ⅵ)的光催化还原效率最高,达99.13%;在真实废水中对U(Ⅵ)的还原率为90.4%,经处理的含铀废水达到国家规定的排放标准。

Based on the photocatalytic reduction of U(Ⅵ),TiO_(2) nanoparticles were prepared by chemical precipitation method.Then,CdS/TiO_(2) composite nanoparticles were prepared by stepwise precipitation method with TiO_(2) as matrix material,and the composite nanoparticles were characterized by scanning electron microscopy,X-ray diffraction and UV-visible diffuse reflectance spectroscopy which could be used to analyze the surface morphology,crystal shape and optical absorption characteristics of the materials.The performance of photocatalytic reduction of U(Ⅵ)in uranium containing wastewater was investigated under visible light irradiation.X-ray diffraction results show that TiO_(2) nanoparticles exist in anatase type and rutile type,while CdS nanoparticles exist in cubic crystal type.Scanning electron microscopy results show that the particle sizes of CdS/TiO_(2) composite nanoparticles range from 30 nm to 50 nm.UV-visible diffuse reflectance spectroscopy results show that compared with TiO_(2) nanoparticles,CdS/TiO_(2) composite nanoparticles have an absorption band from 395 nm to 550 nm,which show the characteristics of a double band gap.The above results indicate that the introduction of CdS in TiO_(2) can expand the light response range of TiO_(2) from ultraviolet region to visible light region,namely,the phenomenon of red shift occurs.Photocatalytic test results show that CdS/TiO_(2) composite nanoparticles show good photocatalytic activity.The photocatalytic reduction efficiency of U(Ⅵ)reaches the highest value of 99.13%when the pH value of simulated wastewater is 6.0,the dosage of CdS/TiO_(2) composite nanoparticles is 1.0 g/L and the photocatalytic reaction time is 2 h.The photocatalytic reduction reaction accords with the kinetic characteristics of quasi first order reaction.In order to verify the photocatalytic reduction effect of CdS/TiO_(2) composite nanoparticles in real wastewater,the real wastewater of a tailing pond was taken as the research object.In the experiment,1.0 g/L CdS/TiO_(2) composite nanoparticles were added for photocatalytic reaction.The results show that the reduction rate of uranium in the real wastewater by CdS/TiO_(2) composite nanoparticles is 90.4%,and the uranium concentration is 0.04 mg/L,which meets the national wastewater discharge standard.The prepared CdS/TiO_(2) composite nanoparticles are visible light photocatalytic materials.The U(Ⅵ)in wastewater can be reduced to U(Ⅳ)by photocatalytic reduction technology.The overall process is simple,environment friendly and has a good prospect of popularization and application.