Function Expansion Of Electrochemical Reactor And Research On Pesticides Wastewater Enhanced Treatment

China is a large country in the production and application of pesticides.The wastewater from pesticide production often contains high COD,high biotoxicity and high salinity.Especially,there are refractory pollutants such as nitrogen-containing and oxygen-containing heterocyclic compounds in wastewater which are hard to be biodegraded.The electrochemical oxidation process could strengthen the removal of organic pollutants.However,the electrochemical oxidation has problems such as low mass transfer efficiency,high energy consumption,and high processing cost which have hindered the industrial application.This research started with the design and optimization of the electrocatalytic oxidation reactor structure in electrochemical oxidation process.Novel tubular(membrane)reactors were constructed to break the mass transfer bottleneck of electrochemical oxidation.What's more,its application in the pretreatment and advanced treatment of pesticide production wastewater were investigated.Based on this,the construction of coulpled reaction system between electrochemical oxidation and other technology was carried out to further improve the efficiency of electron utilization,reduce reaction energy consumption and achieve functional expansion which providing theoretical basis and technical support for the industrial application of electrocatalytic oxidation technology in wastewater treatment.Structure optimization of electrocatalytic oxidation electrode and construction design of relative reactor were carried out.Ti/PbO₂ electrocatalytic tubular electrode was prepared by using hollow titanium tube as the substrate;Ti-RuO₂ eutectic microporous tubular membrane electrode was prepared by using microporous titanium filter tube as the substrate.The tubular electrocatalytic and microporous tubular membrane electrode reactors are respectively assembled through the parallel nesting of cathode and anode.Based on this,the electrochemical performance characterization of the electrode and reactor was carried out and the Flow-by and Flow-through mode on the mass transfer of the reaction system was evaluated.It was found that the mass transfer rates of the two reactors were 5.6 times and 5.8 times higher than those of the plate electrode reactor which significantly enhanced the reaction of electrochemical oxidation and their performance in organic pollutant degradation.Based on the Ti/PbO₂ electrocatalytic tubular reactor,the pretreatment of pesticides wastewater study was carried out.The electrochemical oxidation experiment was carried out with the goal of pretreatment of high-concentration sodium methyl mercaptan(CH₃SNa)pesticide wastewater.The optimized operation parameters were7 m A/cm² of current density,10 g/L of initial CH₃SNa concentration,9 of initial p H and 5 g/L of electrolyte concentration.CH₃SNa removal efficiency of more than 90%of under lower energy consumption and shorter reaction time was achieved.Based on the Ti-RuO₂ microporous tubular reactor,the advanced treatment of pesticides tail water study was carried out.An experiment on the advanced treatment of electrochemical oxidation was carried out with the goal of enhanced treatment of the triazole fungicides tail water.The optimized operation parameters were 5.5 m A/cm² of current density and 5 of initial p H.Concentration of three triazoles contaminants were reduced to less than 10 mg/L with a lower energy consumption and 95%of removal efficiency;Zebrafish Toxicity was tested and the result showed that the biological toxicity of tail water after treatment by the membrane electrode reactor was reduced by more than 3 times.Based on this,combined with the biological aerated filter and electrodialysis process,the high standard reuse of the tail water was achieved.On the basis of the above-mentioned electrocatalytic oxidation reactor,the construction of coupled reactors between electrocatalytic oxidation and other technology was carried out to expand function of electrochemical oxidation.Coupled reactors of“Electrochemical oxidation-electrocatalytic Fenton”(ECF-COTR)was constructed by using anodic oxidation for breaking the complex and cathode reduction of Fe³⁺to accelerate the Fenton reaction.The aim was to realize the function expansion of collaborative oxidation between electrodes and break through the bottleneck of low electrochemical oxidation efficiency and severe slag production of Fenton.Based on the theoretical model of the coupled system of electrochemical oxidation and Fenton,the advanced treatment of organicnitrogen and standard upgrading study of total nitrogen were carried out.Furthermore,the organic nitrogen was removed from 55mg/L to less than 3 mg/L.Biological denitrification filter was combined and completed the tail water standard improvement.A coupled reactor of electrochemical oxidation and anaerobic reduction,namely aerobic fluidized bed reactor based on electric field activation(AFBR-EFA)was constructed.On the basis of cyanide breaking by anodic oxidation,the cathode electron transfer was also used to enhance the microbial anaerobic reduction process to achieve the enhanced reduction and functional expansion of the electrocatalytic reactor.Based on the degradation characteristics of cyanide-containing Isophthalonitrile(IPN)fungicide wastewater under reducing conditions,an electrochemical-assisted cyanide-breaking anaerobic coupled system degradation experiment was carried out.After optimizing the operating conditions,the coupled system achieved 95%of removal efficiency of IPN and cyanide breaking under the condition of higher applied voltage(1.4 V),short hydraulic retention time(3.0 d),moderate salinity(2%Na₂SO₄)and high initial IPN concentration(7.0 g/L).Compared with the performance of electrochemical oxidation and anaerobic processes,it was found that electrochemical oxidation accelerated the proliferation and enrichment of electro-activated bacteria and other bacteria on the electrode surface.In conclusion,high cyanide breaking efficiency and enhanced degradation of IPN assisted by electrochemical oxidation under low energy consumption were achieved.Through the research of this subject,the construction of the electrocatalytic oxidation reactor and the function expansion of coupled system with Fenton oxidation and anaerobic were completed meanwhile the enhanced treatment of pesticide wastewater was achieved.It provided new ideas and new methods for improving the tail water quality of the pesticide industry and reducing the negative impact of industrial sources on the human body and the ecological environment.Furthermore,feasible idea and technical references were provided by using electrochemical oxidation technology for practical engineering application in enhanced removal of refractory and highly toxic organic pollutants and deep reduction of organic nitrogen.