| The composition of fine chemical wastewater is complex.Its water quality has the characteristics of high concentration,high chroma,high difficulty in degradation,high difficulty in biochemistry,high salinity and high toxicity.It is also called"Six types of wastewater",which is difficult to treat.At present,the commonly used methods include physical adsorption and extraction,advanced oxidation and biodegradation.Among them,advanced oxidation is widely used because of its environmental friendliness.Ozone is a substance with high oxidizability.Its oxidation mechanism includes direct oxidation and indirect oxidation processes.However,only ozone oxidation will lead to low utilization rate of ozone and selective removal of organic matter,resulting in incomplete oxidation of organic matter.Therefore,the effluent after ozone oxidation alone cannot meet the discharge requirements.Therefore,in practical application,treatment processes coupled with ozone and other conditions are mostly used,such as O3/H2O2process.This process is considered to be one of the most promising and effective treatment processes in the advanced oxidation process.The principle is that ozone reacts with hydrogen peroxide to generate hydroxyl radical,and then oxidizes organic matter into carbon dioxide and water.Hydroxyl radical is an extremely active oxidant,and its oxidation ability is second only to fluorine.Because this method of generating hydroxyl radical has the advantages of low selectivity and can react with almost all organic substances,it has become a research hotspot,but the generation and process control of hydroxyl radical are difficult.This paper explored the removal characteristics of fine chemical wastewater by separate O3oxidation and O3/H2O2advanced oxidation process,sought the best reaction parameters of O3/H2O2,discussed the interaction between factors by response surface method,controlled the process of hydroxyl radical generation,explored the phenol existing in chemical wastewater,and made kinetic analysis under different operating parameters.The conclusions are as follows:（1）This experiment was taken from the chemical wastewater of Jinwei chemical enterprise.The influent COD was about 25000 mg/L,the influent ammonia nitrogen was about 86 mg/L,the influent SS concentration was about 55 mg/L and the chromaticity was 625 times.It was a typical wastewater with high concentration and high chromaticity.Ozone was generated by ozone generator and the chemical wastewater was pumped into the reactor by peristaltic pump for reaction.The research result showed that the COD removal rate of O3/H2O2oxidation process was significantly higher than that of single O3process.From 43.16%to 69.44%,the biodegradability was greatly improved compared with that without oxidation.The B/C in raw water was only 0.09,which rised to 0.26 after separate O3process,while that after O3/H2O2oxidation increased to 0.35.This was because the hydroxyl radical in the coupling process opens the benzene ring structure of aromatic hydrocarbons in wastewater,and the refractory macromolecules were transformed into small molecules,so the value of B/C would be greatly increased;The chroma removal effect of the two oxidation processes was ideal,and the color had faded after 240 min;The effluent of the two processes was analyzed by UV-vis spectroscopy.It was found that after the oxidation process,the absorption peak of the representative benzene ring and chromogenic group in the raw water became smaller,because the oxidation process cracked the benzene ring and turned it into small molecular organic matter.At the same time,the reaction order of the two different oxidation processes was determined,and it was found that the two processes met the first-order kinetics.It laid a foundation for the analysis of the dynamic process of subsequent O3/H2O2process under different conditions.（2）The chemical wastewater from Jinwei chemical industry was used as the influent of the reactor.The influent water quality conditions were the same as the above conditions.The optimal operating parameters of O3/H2O2advanced oxidation process were explored.The results showed that when p H=9,ozone flow rate was 0.5 L/min and the molar ratio of hydrogen peroxide to ozone was 0.75,the removal rate of COD was the highest,reaching 75.42%;In addition,tert butyl alcohol,carbonate and bicarbonate were selected as free radical inhibitors to explore the effect of inhibitors on COD removal.The results showed that when tert butyl alcohol was added,the removal rate of COD was the lowest,only52.36%,and when it was not added,the removal rate of inhibitors was 72.19%.This was because the addition of tert butyl alcohol inhibits the reaction between free radicals and pollutants,and alcohol hydroxyl groups seized free radicals to form tert butyl alcohol free radicals,A stable superconjugation structure was formed,and the removal rate of COD decreased significantly after adding carbonate ion and bicarbonate ion,which were54.26%and 59.36%respectively,which was determined by the reaction rate constant between them and hydroxyl radical;The kinetic analysis of O3 flow,pH and H2O2dosage in O3/H2O2process showed that the degradation process conforms to the first-order kinetic reaction.The reaction rate constant was 0.01265 when O3flow was 0.5 L/min,0.01839 when p H was 9,and 0.01744when H2O2dosage was 50 mg/L;The response surface method was used for multi factor analysis and fitting with the model of COD degradation by advanced oxidation.The results showed that the degradation model of COD was Y=2.45+0.472A+4.86B+123.45C-5.2BC-0.0038A2-0.085B2-99.26C2,and the interaction between the two factors from large to small was p H and O3flow>H2O2dosage and p H>H2O2dosage and O3flow;（3）Phenol was used as the research object to explore the effects of different operating conditions on phenol removal characteristics.The influent phenol concentration was 100 mg/L and p H was 6.5.The factors of phenol removal rate were studied by controlling variable method.The results showed that when p H=9,ozone flow was 0.5L/min,ozone concentration was 66 mg/L and hydrogen peroxide dosage was 50 mg/L,the phenol removal rate was the highest,94.26%.Moreover,the influence of initial phenol concentration on phenol removal efficiency was explored.It was found that when the initial concentration was 50 mg/L,the phenol removal rate was the highest,98.11%,In addition,the reaction kinetics of each factor was analyzed respectively.When exploring the effect of ozone flow on phenol removal,the samples were taken for kinetic analysis at different times.It was found that its degradation accorded with the first-order kinetic process.When the ozone flow was 0.5 L/min,the constant of reaction rate was the largest,which was 0.05127,and its correlation coefficient R2was more than 0.97;When exploring the concentration of hydrogen peroxide,it was found that the rate constant was0.05217 at 50 mg/L per hour;The initial phenol concentration also had a great influence on the phenol removal rate,reaching the maximum at 50 mg/L,which was 0.06517;Finally,when exploring the effect of initial p H on phenol efficiency,it was found that the rate constant was 0.04836 when pH=9. |
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