Preparation Of Electro-catalytic Oxidation Anodes And Their Applications In Herbicide Wastewater Treatment

In recent years,herbicides are used in agriculture worldwidely for that they can be selectively used and be degraded easily in soil.Due to partial water solubility,they may appear as pollutants in groundwater,surface water and in drinking water alike,and do great harm to the human and natural environment..The use of electrochemical oxidation for the treatment of herbicide wastewater has undergone rapid development in recent years because of its simple equipment and can't produce secondary pollution.Ti/SnO₂-Sb₂O₃/PbO₂ anodes were prepared by brush coating with high temperature oxidation and electro-deposition method.The electrochemical behaviour of imazethapyr,chlorimuron-ethyl, pyrazosulfuron-ethylusing,Cyclohexanone on the surfaces of platinum,glassy carbon and Ti/PbO₂ anode was investigated by cyclic voltammetry in the paper.The cyclic voltammograms were obtained in different conditions by chaging the bulk electrolysis,the concentration of sample,pH of the electrolysis and the petential scan rate.The results showed that these types of herbicide can be degraded well on the Ti/SnO₂-Sb₂O₃/PbO₂ anode surface in Na₂SO₄ medium at weak acid condition.The Ti/SnO₂-Sb₂O₃/PbO₂ electrode was used as the anode in the degradation of imazethapyr,chlorimuron-ethyl,pyrazosulfuron-ethylusing and cyclohexanone.The factors such as current density,electrolyte,pH value,space between the electrodes were investigated,and the optimum electrolytic reponse condition were obtained.The electrochemical decomposition mechanism of such herbicide imazethapyr were studied by UV-VIS spectrophotometry.Imazethapyr was mineralized directly when using Na₂SO₄ as the electrolyte,while a kind of intermediate product were formed rapidly and then mineralized fast when using NaCl as the electrolyte,chlorimuron-ethyl and pyrazosulfuron-ethylusing were mineralized directly when using Na₂SO₄ as the electrolyte also.The Chemical oxygen demand(COD) was monitored in imazethapyr, chlorimuron-ethyl,pyrazosulfuron-ethyl degradation processes by potassium dichromate method.The results showed that the COD was removed more than 90%.The results showed that the Ti/SnO₂-Sb₂O₃/PbO₂ electrode has a longer service life and catalytic activity,it was a superior electro-catalytic oxidation anode material for the degradation of herbicide wasterwater.Na₂SO₄ is a good electrolyte because it can extend the life of anode and can't produce secondary pollution,its intermediate products are propitious to the degradation of organic compounds and can improve the current efficiency.