Degradation Of Carbaryl From Water Over Three Kinds Of The Titanium Oxide Anodes

In recent years,the problem of pesticide pollution in water has aroused wide concern all over the world.Due to its variety and difficulty in removal,a series of environmental problems have been caused by continuous accumulation in the water environment,which not only has an important impact on aquatic organisms,but even affects the entire ecosystem.Due to conventional water treatment technology is difficult to effectively remove pesticide in water,so you need to develop more efficient pesticide removal techniques of water.At present,the advanced oxidation technologies were widely used in the study of the pesticide removal,the electrochemical oxidation of the pesticide has a better removal effect,its research has become a research hotspot and difficulty in the field of water treatment.However,although electrochemical oxidation has a high removal rate of organic matter,there are problems such as slow mass transfer rate and low current utilization rate.It is necessary to continue research and development of more efficient electrochemical anodes.Therefore,this study intends to develop Ti/Ti₄O₇,Ti/Ti₄O₇-Pb O₂-Ce and Ti/Ti₄O₇-NTA with high activity.The surface morphology and electrochemical properties of Ti/Ti₄O₇,Ti/Ti₄O₇-Pb O₂-Ce and Ti/Ti₄O₇-NTA anodes were analyzed.Carbaryl removal rate,total organic carbon removal rate,mineralization current efficiency and reaction kinetic parameters of carbaryl were compared among three Ti₄O₇ anodes,and the removal efficiency of carbaryl and other organic pesticides in water by electrochemical oxidation was analyzed.To identify carbaryl electrochemical oxidation intermediates in water,explore the electrochemical degradation path of carbaryl,and analyze the impact of its degradation intermediates on the toxicity of solution,the main research conclusions are as follows:（1）Preparation and characterization of three kinds of Ti₄O₇ anodes:Ti/Ti₄O₇ anodes were prepared by plasma spraying,Ti/Ti₄O₇-Pb O₂-Ce anodes by electrochemical deposition,and Ti/Ti₄O₇-NTA anodes by electrochemical oxidation-self-doping reduction.The structure and electrochemical characteristics of three Ti₄O₇ plate anodes were analyzed by comparing their surface morphology and electrochemical properties.The results show that the prepared Ti/Ti₄O₇ anode has good coating coverage,oxygen evolution potential of 2.15 V vs.SCE,and relatively good electrocatalytic activity.The surface of Ti/Ti₄O₇-Pb O₂-Ce anode has obvious particulate matter,which is conducive to the adsorption of target pollutants.The oxygen evolution potential of Ti/Ti₄O₇-Pb O₂-Ce anode can reach 2.2V vs.SCE,and it has good electrocatalytic activity.The surface of Ti/Ti₄O₇-NTA anode is etched to form many nanotube-like structures,which greatly increases the specific surface area of the reaction,and the oxygen evolution potential of Ti/Ti₄O₇-NTA anode can reach 3.1V vs.SCE,showing good electrocatalytic activity.（2）Degradation efficiency of carbaryl in water by Ti₄O₇ anode.Compared the degradation and mineralization effects of carbaryl in water by three Ti₄O₇ plate anodes,and analyzed the characteristics of electrochemical removal of carbaryl in water by Ti₄O₇ anode.The electrochemical degradation kinetics of carbaryl at Ti/Ti₄O₇ anode was studied under the conditions of different current density,initial concentration of carbaryl,electrolyte type and p H.The results showed that Ti/Ti₄O₇ anode（90.5%）Ti/Ti₄O₇-Pb O₂-Ce anode（100%）and Ti/Ti₄O₇-NTA anode（96.1%）had higher removal efficiency of carbaryl in water.Compared with Ti/Ti₄O₇ anode（58.3%）,the TOC removal rate of Ti/Ti₄O₇-Pb O₂-Ce anode（78.2%）and Ti/Ti₄O₇-NTA anode（80.2%）is higher.And the mineralization current efficiency of the three Ti₄O₇ anodes decreased gradually with the increase of reaction time.（3）Study on electrochemical degradation products and pathways of carbaryl degradation intermediates were identified by HPLC-MS and GC-MS in Ti/Ti₄O₇ anodic electrochemical degradation.The electrochemical oxidation and degradation path of carbaryl was predicted according to the variation rule of intermedium products.Through the quantitative structural-activity relationship of organic matter,the influence of carbarylelectrochemical degradation intermediates on the toxicity of solution was analyzed.The study showed that carbaryl was gradually degraded into other small molecular organics during the electrochemical degradation of carbaryl by Ti/Ti₄O₇ anodes.Based on the test to determine the middle of the 19 kinds of products,respectively A（m/z=202）,B（m/z=204）,C（m/z=189）,D（m/z=145）,E（m/z=161）,F（m/z=193）,G（m/z=155）,H（m/z=219）,I（m/z=176）,J（m/z=108）,K（m/z=170）,L（m/z=46）,M（m/z=49）,N（m/z=47）,O（m/z=70）,P（m/z=90）,Q（m/z=192）,R（m/z=116）and S（m/z=118）.Based on these 19intermediates,a possible degradation path of carbaryl by electrochemical oxidation was deduced.The toxicity of these 19 intermediates was not as strong as that of carbaryl,among which the intermediates with higher toxicity were B（M/z=204）and E（M/z=161）,which had higher response to chronic toxicity and acute toxicity of aquatic organisms such as fish,daphnia and algae.Ti/Ti₄O₇,Ti/Ti₄O₇-Pb O₂-Ce and Ti/Ti₄O₇-NTA plate anodes with high activity were successfully developed.The removal efficiency of carbaryl from water by anodic electrochemical oxidation of three Ti₄O₇ plates was investigated.The reaction path of anodic electrochemical degradation of carbaryl on Ti₄O₇ plate was proposed,and the effect of degradation intermediates on the toxicity of solution was analyzed.