Research Of Electric Catalytic Oxidation Technology On Typical Nitrogen Heterocyclic Compounds And Its Application In The Pharmaceutical Wastewater

Typical nitrogen heterocyclic compounds,such as pyridine and quinoline,widely used in medicine,pesticide,chemical and other industries,and their structure stability is not easy to degrade.Besides,its pharmaceutical wastewater is difficult to handle due to the high toxicity and complicated composition.Common used methods of adsorption and coagulation in wastewater pretreatment technology were not economic and efficient to degrade nitrogen heterocyclic compounds,and difficult to improve the biodegradability and reduce its toxicity.What's more,Photocatalysis and Fenton technology can effectively degrade nitrogen heterocyclic compounds,but it rarely explained the degradation mechanism of the system.Electrochemical technology is a kind of no secondary pollution and clean advanced oxidation technology,which needs no chemical reagents.In this paper,based on the refractory characteristics of nitrogen heterocyclic compounds,we developed a new Ti/IrO2-Sb/Ce-PbO2 electrode with high electric catalytic activity and well stability.And we used electric membrane oxidation technology to efficiently deal with pyridine,quinoline and its pharmaceutical wastewater.Moreover,the paper roundly analysed the pyridine and quinoline degradation mechanism,paying attention to discuss the direct electrooxidation and indirect electrooxidation of their contribution in the process.In this paper,the main research content is described below:(1)Optimizing Ce doped electrode structure by evaluating the electrochemical performance.For nitrogen heterocyclic compounds refractory,the article studyed the different current density and doping Ce content to the preparation of modified Ti/IrO2-Sb/Ce-PbO2 electrode.The research results showed that:the coating electrode surface was?-PbO2 with some Ce content.And the higher current density was,the coating electrode surface structure got more closely.Electrochemical polarization curve and electrochemical impedance spectroscopy also showed that the increase of current density made the electrodes with higher oxygen evolution potential and lower charge transfer resistance.So the best optimization of current density was 40 mA/cm2.However,excess metal Ce would make lead dioxide plating structure fall off easily,reducing the oxygen evolution potential and catalytic activity.The oxidative degradation effect and degradation rate of Ti/IrO2-Sb/Ce-PbO2 electrode was greater than that of commercial Ti/IrO2-Sb,Ti/IrO2-RuO2 and PbO2 electrodes,and the mineralization effect of mixture of pyridine and quinoline solution reached 65.05%.(2)Optimization of electrical catalytic processes for pyridine degradation and getting its key control parameters.The paper studyed the electric catalytic oxidation treatment of pyridine oxidation degradation characteristics,influencing factors,mechanism and toxicity changes.The research results showed that:we had built a set of electrochemical device with cation exchange membrane,which could integrate the reduction reaction and oxidation reaction.Compared the degradation of pyridine by the electrooxidation,electric oxidation-reduction,electric oxidation-reduction-oxidation with membrane reactor and electrooxidation without membrane four different electrochemical technology,we obtained the best technology was electric membrane oxidation technology.Electrochemical properties of pyridine showed it could more easily open loop under weak alkaline and alkaline conditions.Optimum parameters of electric catalytic oxidation pyridine as:30 mA/cm2 current density,pH8,0.05 MNa2SO4 electrolyte,electrolytic 100 min,and the initial concentration of 1000 mg/L pyridine.And ten consecutive batches of running proved that the electrode and the reactor degraded pyridine stably.We also found indirect oxidation of pyridine oxidation contribution rate is far less than direct oxidation.Besides,N in pyridine was proved through oxidative degradation to formamide by GC-MS.What's more,the B/C increased to 0.33 after electric catalytic oxidation,and the toxicity reduced more than 70.64%.(3)Optimization of electrical catalytic processes for quinoline degradation and getting its key control parameters.The paper studyed the electric catalytic oxidation treatment of quinoline oxidation degradation characteristics,influencing factors,mechanism and toxicity changes.The research results showed that:compared the degradation of quinoline by the electrooxidation,electric oxidation-reduction,electric oxidation-reduction-oxidation with membrane reactor and electrooxidation without membrane four different electrochemical technology,we obtained the best technology was electric membrane oxidation technology.Electrochemical properties of quinoline showed it could more easily open loop under neutral and alkaline conditions.Optimum parameters of electric catalytic oxidation quinoline as:30 niA/cm2 current density,pH7.40s 0.05 MNa2SO4 electrolyte,electrolytic 180 min,and the initial concentration of 700 mg/L.And ten consecutive batches of running proved that the electrode and the reactor degraded quinoline stably by two different electrolytic reaction time.We also found quinoline during the degradation process in 313 nm absorbance reduced constantly by UV,and the absorption peak changed during 250 nm-300 nm.Indirect oxidation had a certain influence on the degradation of quinoline.Besides,quinoline was proved to transform 2-amino-benzaldehyde by GC-MS.What's more,the B/C increased to 0.31 after electric catalytic oxidation,and the toxicity reduced more than 61.77%.(4)In view of the actual pharmaceutical wastewater with membrane electrical catalytic oxidation degradation and technological parameters.In order to research the availability of the electrodes and the device,the article was studied by self-made Ti/IrO2-Sb/Ce-PbO2 electrode and a membrane oxidation device to deal with a certain plant nitrogen heterocyclic compounds in pharmaceutical wastewater.Investigating the current density,initial concentration,solution pH,electrolytic time four different parameters on the wastewater treatment of COD,TN,biochemical and toxic effects.The research results showed:considering the degradation effect of COD and TN after wastewater treatment and power consumption,the best technological parameters for electricity catalytic oxidation of pharmaceutical wastewater:30 mA/cm2 current density,pH9.80 and electrolytic time 3 h.Wastewater after multiple dilution,the COD,TN and luminescent bacteria toxicity index had a higher removal rate than that of original wastewater concentration.And the B/C with different dilution concentration was more than 0.30.Moreover,COD,TN,and power consumption value was proved that the electrodes and reactor stability of nitrogen heterocyclic compounds in pharmaceutical wastewater treatment after ten consecutive batches running.Besides,the COD degradation could be around 44.05%and TN could remove 68.05%or so.