Study On Degradation Of Nitrophenol Wastewater By Microwave Coupled Fenton Process

Microwave coupled Fenton degradation is an emerging wastewater treatment technology in recent years,which has attracted the attention of many researchers.However,the current microwave-coupled Fenton degradation technology has the disadvantages of single target pollutant and poor catalyst recovery performance in the treatment of nitrophenol wastewater.In this paper,a 2Fe₃O₄-Bi OCl catalyst with good microwave response characteristics and magnetic recovery was prepared,and a microwave-coupled 2Fe₃O₄-Bi OCl/H₂O₂ system was constructed,which achieved good results in the degradation of practical wastewater and is expected to be applied in the large-scale treatment of industrial wastewater.First,a variety of Fe₃O₄-Bi OX（X=Cl,Br,I）catalysts were prepared.Through the degradation experiment of 4-nitrophenol solution,the most suitable 2Fe₃O₄-Bi OCl catalyst for microwave Fenton reaction was screened.The physicochemical properties such as surface element distribution and magnetic recyclability were characterized.Then the catalyst was used in the treatment of 4-nitrophenol simulated wastewater,and the optimal process parameters for the operation of the reaction system were obtained.At the same time,the catalyst has good magnetic recovery,and the total recovery rate after 7 times of usage is 78.71%（wt.）.Through the free radical quenching experiment,it was confirmed that at least three important reactive species were produced during the reaction,namely·OH,·O₂^-and h+,Among them,·OH is dominant.It is pointed out that the generation of reactive species on the catalyst surface follows the photocatalytic-heterogeneous Fenton-like catalysis mechanism under microwave environment.At the same time,using GC-MS and HPLC,a roadmap for the degradation of 4-nitrophenol was drawn.Then,some problems such as reaction stage,reaction kinetics and element distribution after reaction were explored.Furthermore,the degradation routes and reaction kinetics of 4-aminophenol,3-nitrophenol and 2,6-dimethyl-4-nitrophenol were studied on the basis of 4-nitrophenol.The general rules for the degradation of nitrophenols（and corresponding amino phenols）are summarized.The system was applied to the degradation of real wastewater and achieved excellent degradation effect.The removal efficiency of COD was 87.41%,the removal efficiency of TOC was 83.41%,the removal efficiency of TN was 72.34%,and the BOD₅/COD was from 0.11 to 0.68.At the same time,it is estimated that the combined energy consumption and material cost of the reaction system is about 95.87 yuan/ton,and the relative price is low.It can be seen that the reaction system has a good industrialization prospect.