The Research Of COD Sensor Electrode And Its Performance Of Photoelectrocatalytic Oxidizing Organics

At present,the problems about the water pollution in our country are more and more serious,which urgently need effective regulation and proper dispose.Chemical Oxygen Demand（COD）is an important index of water organic pollution degree.The real-time and fast determination of COD is an important premise of governing the water pollution.Therefore,various methods of COD determination had been researched continuously.Among them,the photoelectrocatalytic method of COD determination using TiO₂nanotube arrays electrode COD sensor has received widespread attention,because of its advantages,such as efficient,fast,highly accurate,clean,pollution-free and so on.Based on the previous studies by our research group,this article explored the oxidation performance of the humus acid existed in the water by TiO₂ nanotube arrays electrode.And the visible light response WO₃/TiO₂ COD sensor was also researched in this article.Fulvic acid is a typical refractory organics existed in natural water bodies,as well as an important COD component of natural water.The COD determination of fulvic acid is always a tough difficulty.This article investigated the oxidation performance of common organics which have hydroxyl in the photoelectrocatalytic system of COD determination firstly.The result showed methanol,ethanediol,glycerol and methanoic acid could be oxidized completely,their oxidation ratio are all close to 100%.Then the oxidation performance of fulvic acid was studied.The result showed the oxidation ratio of fulvic acid is less than 41%,which means fulvic acid could not be degraded completely.After further exploring the effect of adding easily oxidizable organics on the degradation performance of fulvic acid,the result showed that the addition of methanol,ethanediol,glycerol and methanoic acid could improve the degradation ratio of fulvic acid previously.When the COD concentration rate between methanol,ethanediol,glycerol,methanoic acid and fulvic acid are 8:1,4:1,3:1 and 3:1 respectively,fulvic acid could be degraded completely.The promotion mechanism is related to the adsorption properties of easily oxidizable organics on the surface of photoanode and the generation of abundant hydroxyl radicals which have well ability of oxidation.As a result,a COD determination method of fulvic acid by adding easily oxidizable organics was built in this article.Based on the match of lattice and Fermi energy level between TiO₂ and WO₃,this article modified TiO₂ by a hydrothermal process on the surface of WO₃ nanopores electrode,which is prepared by the anodic oxidation,in order to produce a novel visible light response WO₃/TiO₂ electrode.The electrode shows well incident photon-to-electron conversion efficiency to the wavelength ranged in 350-425 nm.Meanwhile,it appeared a better photoelectrocatalytic stability than WO₃ nanopores electrode.This article used the visible light response WO₃/TiO₂ electrode as COD sensor and analyzed its COD determination.The result shows that WO₃/TiO₂ electrode has a good COD sensing performance,the relative standard deviation of 10times determination was only 0.20%.At the same time,the COD determination of representative organics showed a well linear relationship between the electric quantity generated in the photoelectrocatalytic degradation and the theoretical COD of the organics.