MnWO_(4)/WO_(3)复合光催化剂的制备及其在含油废水处理中的应用

Preparation of MnWO_(4)/WO_(3) composite photocatalyst and its application in the treatment of oil-containing wastewater

本论文通过水热法制备WO_(3)载体,随后以硝酸锰为前驱体,采用浸渍、焙烧方法原位合成了一系列x%-MnWO_(4)/WO_(3)样品。采用XRD,SEM,EDS,TEM,HR-TEM,BET,UV-vis DRS,PL和捕获剂实验对样品的晶体结构,形貌,光物理性质和光催化降解含油废水的机理进行了研究。通过XRD,SEM,EDS,TEM和HR-TEM分析证明x%-MnWO_(4)/WO_(3)样品的成功合成,在MnWO_(4)含量较低的1%-MnWO_(4)/WO_(3)样品,WO_(3)载体分散性较好,MnWO_(4)小颗粒均匀分散在WO_(3)表面,而当MnWO_(4)含量增加时,在焙烧过程中WO_(3)发生团聚现象,导致MnWO_(4)在WO_(3)表面分散性不好。在可见光催化降解含油废水的实验中,所有x%-MnWO_(4)/WO_(3)样品的光催化活性较纯WO_(3)样品均有不同程度提高,1%-MnWO_(4)/WO_(3)样品的光催化活性最高,其光催化降解含油废水的降解率达到了95.2%,一级反应动力学常数达到了0.4723 h^(-1),分别为纯WO_(3)样品的3.2和7.9倍。通过BET,UV-vis DRS,能带结构分析和PL分析,证明x%-MnWO_(4)/WO_(3)样品的光催化活性较纯WO_(3)样品光催化活性提高是由于其较高的光谱响应范围和较高的光生载流子分离效率。结合结构形貌分析证明1%-MnWO_(4)/WO_(3)样品的光催化活性最高的原因是由于WO_(3)分散性较好,合成的MnWO_(4)小颗粒分散在WO_(3)表面,二者之间能够形成的有效接触面积大,光生载流子的分离效率最高。牺牲剂实验证明·O_(2)^(-),h^(+)和·OH都参与了光催化降解含油废水反应。

WO_(3) was prepared by a hydrothermal method,and then a series of x%-MnWO_(4)/WO_(3) samples were synthesized using manganese nitrate as the precursor by precipitation and calcination method.The crystal structure,morphology,photophysical properties and photocatalytic degradation mechanism of the samples were studied by XRD,SEM,EDS,TEM,HR-TEM,BET,UV-Vis DRS,PL and sacrificial agent experiments.Through XRD,SEM,EDS,TEM and HR-TEM analysis,it was proved that x%-MnWO_(4)/WO_(3) samples was successfully synthesized.In 1%-MnWO_(4)/WO_(3) sample,the dispersion of WO_(3) carrier was good,and the small particles of MnWO_(4) were evenly dispersed on the surface of WO_(3).However,with the further increasing of MnWO_(4) amount,WO_(3) agglomeration occurred in the process of calcination,resulting in poor dispersion of MnWO_(4) on the WO_(3) surface.In the experiments of visible-light-driven catalytic degradation of oil-containing wastewater,photocatalytic activity of all the x%-MnWO_(4)/WO_(3) samples was improved to varying degrees compared with that of the pure WO_(3) sample.The photocatalytic degradation rate of oil-containing wastewater of 1%-MnWO_(4)/WO_(3) sample is 95.2%and the kinetic constants of the first order reaction is 0.4723h^(-1),which are 3.2 and 7.9 times of those of pure WO_(3) sample,respectively.Based on BET,UV-Vis DRS,energy band structure analysis and PL analysis results,it was proved that the improved photocatalytic activity of x%-MnWO_(4)/WO_(3) sample is due to its wider spectral response range and higher photo-induced electrons and holes separation efficiency.Combined with the structure and morphology analysis,it was proved that the highest photocatalytic activity of 1%-MnWO_(4)/WO_(3) sample is due to the good dispersion of WO_(3) and the small MnWO_(4) particles are evenly dispersed on the surface of WO_(3),thus,the effective contact area can be formed between MnWO_(4) and WO_(3),which finally results in the highest separation efficiency of photogenerated electrons and holes.The sacrificial agent experiments showed that·O_(2)^(-),h^(+)and·OH all participate in the photocatalytic degradation of oil-containing wastewater.