| With the rapid development of industrialization,environmental pollution has become increasingly serious.As an important chemical raw material,phenol has a wide range of applications,and has high biological toxicity in itself and intermediate products.At the same time,humic acid is an important precursor substance for disinfection by-products in water treatment processes.Due to their stable properties,high biological enrichment and great harm,they have become the focus of attention.Vacuum UV-Fenton(VUV-Fenton)technology treats high concentrations of phenol and humic acid,and often encounters the problem that the chemical oxygen demand(COD)cannot be decreased quickly when it is treated to a certain degree,which we call the "platform" phenomenon.Aiming at the "platform" phenomenon encountered in the treatment of refractory phenol and humic acid by VUV-Fenton technology,this project intends to realize the phenol and humic effect by studying the synergistic promotion effect of easily degradable substances on phenol and humic acid in the VUV-Fenton system.The further mineralization of acids,based on the perspective of free radicals,explores the mechanism by which easily degradable substances promote deep mineralization of refractory substances.Factors affecting the experimental results show that when the initial concentration of phenol is 1000 mg/L,when the p H is 3,the concentration of H2O2 and Fe2+ is 37.5 mmol/L and 6 mmol/L,the removal rate of COD in the system reaches 85%,and the system appears "Platform" phenomenon.Adding formic acid,methanol,and tert-butanol to the system before starting the reaction not only accelerates the early reaction rate,but also promotes the deep mineralization of phenol;the concentration and method of addition have a greater impact on the catalytic oxidation efficiency of phenol.With increasing concentration,the rate of COD removal in the system increased significantly.After 180 min,the COD removal rate of the system with three doses of easily degradable substances was as high as 90%.Fourier transform infrared analysis results show that during the degradation of phenol,catechol,benzoquinone and other difficult-to-degrade intermediate products are generated,which may be the cause of the "platform" phenomenon.Based on the VUV-Fenton system,the degradable materials promote the deep mineralization of phenol and humic acid.The results show that the addition of easily degradable substances can promote the deep mineralization of phenol and humic acid,but promote the phenol mineralization better than hum.Acid;at the same time,the concentration and dosage of easily degradable substances also have a significant effect on promoting the deep mineralization of phenol and humic acid.With the increase of the concentration of addition,the effect of promoting deep mineralization of phenol and humic acid is better.It is better to promote the effect of adding more degradable substances than once.The rate of formation of H2O2 in the early stage of ultraviolet photolysis of easily degradable substances(formic acid,methanol,tert-butanol,sucrose and chloroacetic acid)is basically consistent with the tendency of COD to decrease when the "platform" is broken in the phenol system.The effect of H2O2 concentration on the mineralization of phenol Experiments show that ·OH is not a key factor in promoting the deep mineralization of phenol.The EPR test results show that ·OH exists in the system,CO2-? are generated after the addition of formic acid,and the number of free radicals in the system increases.The mechanism of deep mineralization of easily degradable substances to promote refractory substances can be attributed to the formation of free radical chain reaction induced by easily degradable organic matter. |
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