Study And Application Of Electrochemical Detection And Photoelectrocatalytic Degradation On Diuron

With the development of human society,more and more attentions have been paid to the environmental question caused by environmental pollution.It is very significant to develop new techniques and new methods for analysis and degradation of environmental pollutants because most environmental pollutions were resulted from chemical substances.The long-term epidemiological studies indicated that environmental pollution has already influenced human health seriously.At present,the study of organic pollutants has become an interesting issue of environmental science field because the toxicity of organic pollutants is greater than that of inorganic pollutants.However,the undermining influence of the remnants of pesticides and herbicides in the foodstuff to human health come to near with the excessive usage.Therefore,there is an urgent need to develop rapid,simple and economic methods for the analysis and removal of pollutant of pesticides/herbicides.The extraordinary electronic property of CNTs enables them to facilitate the electron transfer when they act as electrode materials.Furthermore,the properties include excellent adsorption capability,great specific surface and various functional groups linked on CNTs have endued them with special electrocatalytic effect to the electrochemical behavior of some species.Thus,CNTs modified electrodes exhibit superior electrochemical properties to many other electrodes.TiO₂ is widely used as the photocatalyst during the photocatalytic process,because it is nonphoto corrosive,nontoxic,and capable of photooxidative destruction of most organic pollutants.While there are still some shortcomings,including relatively low specific surface area and weak photocatalytic efficiency of bulk TiO₂ in the TiO₂ film. The large surface area of TiO₂ film could lead to more efficient light harvesting and photogenerated charge.To improve these disadvantage,a lot of investigation has been devoted:Firstly,to avoid the aggregation and the difficulty of the catalyst recovery existing in the suspension system,the catalyst was directly produced on the surface of titanium sheet;Secondly,photoelectrocatalytic technology has been employed to enhance the photocatalytic efficiency;Thirdly,titania nanotubes has been prepared and it has high photocatalytic efficiency because of its large surface area;Finally,QD-CdS modified TiO₂ electrode has been prepared to improve the photocatalytic efficiency. The whole paper can be classified into following four parts:â… .Overview(Chapter 1)The review of modern environmental pollution was mentioned at the first place. The current theories,methods and instruments for pollutant analysis and determination were summarized in this part.A detail outline and of the semiconductors,such as TiO₂, quantum dots and their applications were introduced.â…¡.Electrochemical Sensor Based on Multi-wall Carbon Nanotubes for the Detection of Diuron(Chapter 2)In this study,multi-wall carbon nanotubes(MWCNTs)were used for fabrication of electrochemical sensor for the detection of herbicide diuron.It exhibited good electrochemical response at the MWCNTs electrode surface.The electrochemical characterization and voltammetric performance of diuron were evaluated using Cyclic Voltammetric(CV)and Differential Pulse Voltammetric(DPV).The amount of MWCNTS and pH of the electrolyte have been optimized.Under the optimized condition,electrochemical sensor modified with MWCNTs exhibited promising voltammetric performances,and the current response was well linear over the 0.14～14.32μg/mL diuron range with the detection limit of 0.03μg/mL(S/N=3).The recoveries of diuron in samples are between 94%and 105%,which shows it is a sensitive and stable method,and has promising application in food inspection.â…¢.Photoelectrocatalytic Activity of Highly Ordered TiO₂ Nanotube Arrays Electrode for Diuron Degradation(Chapter 3)A highly ordered titanium dioxide nanotube arrays(HOTDNA)electrode was prepared in hydrofluoric acid solution by electrochemical anodization technique on a pure titanium sheet.The HOTDNA electrode was characterized by FE-SEM microscopy,X-ray diffraction and UV-vis spectra.The linear-sweep photovoltammetry response on the HOTDNA electrode is also presented in this work.The photogenerated current of 0.3 mA/cm² was observed significantly upon illumination with applied potential of 0.6V in the UV regions at the central wavelength of 253.7nm. Photoelectrocatalytic(PEC)and photocatalytic(PC)activities of the HOTDNA electrode were evaluated in the degradation of Diuron in aqueous solution.A set of optimized conditions such as anodic potential,calcinations temperature,and Diuron concentration on the PEC activity was investigated.The PEC and PC activities of HOTDNA electrode were compared in this paper.We concluded that the HOTDNA electrode was an effective method for achieving an enhanced Diuron degradation.â…£.Photoelectrocatalytic Activity of CdS Quantum Dots Sensitized TiO₂ Nanotube-Array Photoelectrode for Diuron Degradation(Chapter 4)In this study,CdS quantum dots sensitized TiO₂ nanotube-array (QDs-CdS/HOTDNA)photoelectrodes were successfully prepared by depositing CdS quantum dots onto the surface of HOTDNA electrodes.The QDs-CdS/HOTDNA electrode was characterized by FE-SEM microscopy and UV-vis spectra.The linear-sweep photovoltammetry response on the HOTDNA electrode is also presented in this work.The comparison of Diuron degradation between HOTDNA electrode and QDs-CdS/HOTDNA electrode was made to demonstrate the importance of QD-CdS sensitization in the process of photoelectrocatalytic degradation of Diuron.The mechanism of photoelectrocatalysis on QDs-CdS/HOTDNA electrode was also discussed in this work.