Degradation Of Environmental Estrogens By Heterogeneous Catalytic Ozonation

With the rapid development of economic and society,environmental estrogens pollution has aroused more and more attention,and the environmental estrogens that discharged with industrial wastewater will lead to serious damage to the ecological environment and human health,therefore it is significant to find efficient processing methods.Heterogeneous ozone oxidation method,with high oxidation efficiency,easy recovery and less secondary pollution,has good prospects for the removal of environmental estrogens from wastewater.In this study,heterogeneous catalytic oxidation was applied for the degradation of bisphenol A and 2,4-dichlorophenol,and the effects and laws of heterogeneous catalytic oxidation were studied.（1）The catalysts D851-Cu and D851-Fe were prepared by impregnation method using D851 chelating resin as carrier,and were used to catalyze ozonation for the degradation of bisphenol A and 2,4-dichlorophenol.According to the removal rate,D851-Cu-5 and D851-Cu-1 were selected for catalytic ozonation,and were characterized with SEM-EDS,FTIR,BET and TGA.It was found that Cu was successfully loaded on D851,and there were no significant changes occurred in resin skeleton before and after loading,and the thermal stability was certainly improved.The dissolution rate of metal ions under different pH was tested and the results showed that Cu was not eluted,indicating that the two catalysts had good stability.（2）In the experiments of the degradation of bisphenol A and 2,4-dichlorophenol by ozone oxidation alone,the effects of ozone dosage,flow rate,pH,initial concentration and temperature were examined.It could promote the degradation of bisphenol A and 2,4-dichlorophenol when ozone dosage and temperature increased.The increases in flow rate and pH could lead to a decrease in the removal rate of bisphenol A and 2,4-dichlorophenol,and the higher the initial concentration was,the lower the removal rate of bisphenol A and 2,4-dichlorophenol achieved.（3）The selected catalysts were used to catalyze the oxidation of bisphenol A and2,4-dichlorophenol,respectively,and the effects of pH,ozone dosage,catalyst dosage,flow rate,initial concentration and temperature were investigated.Compared with ozone oxidation alone,the catalyst could promote the degradation of bisphenol A and2,4-dichlorophenol.With ozone dosage and temperature increasing,the removal efficiency of bisphenol A and 2,4-dichlorophenol improved,and the lower the flow rate or the initial concentration was,the higher the removal rate of bisphenol A and 2,4-dichlorophenol could reach.It was not conducive to the catalyst under alkaline conditions,and under weak acidic and neutral conditions,bisphenol A and 2,4-dichlorophenol had high removal efficiency.（4）The free radical inhibition experiments showed that tert-butanol had a certain inhibitory effect on the catalytic ozone oxidation system,indicating that there are both direct ozone oxidation and indirect ozone oxidation in the catalytic ozone oxidation system.After three times of the use of D851-Cu-5 and D851-Cu-1,the removal rates of bisphenol A were 89.88%,88.59%and 87.41%,and the removal rates of 2,4-dichlorophenol were 92.06%,90.91%and 89.18%,indicating that the two catalysts showed better reusability.（5）Both the fast stage and the slow stage existed in the degradation of bisphenol A and 2,4-dichlorophenol and fitted the first-order reaction kinetics.The reaction rate constant in the fast stage is obviously higher than that in the slow stage.The effects of various factors on the removal of bisphenol A and 2,4-dichlorophenol were mainly achieved by changing the reaction rate.The faster the reaction rate is,the better the removal effects could achieve.And compared with the single ozone oxidation system,the reaction rate of the catalytic ozonation system under the same conditions is higher,indicating that the catalyst could indeed increase the reaction rate,thereby increase the removal efficiency of pollutants.（6）Detecting changes in solutions pH and COD,it was found that the pH of the solutions decreased,and the changes of COD removal were not obvious,indicating that organic acids and other substances may be generated,resulting in the decrease in the pH of the solution and the smaller increase in the COD removal rate.The transformation products were analyzed by GC-MS to infer possible degradation pathways of bisphenol A and 2,4-dichlorophenol.Bisphenol A first broke the benzene ring to form a phenolic intermediate,which is then continuously oxidized to organic acids,etc.,and eventually oxidized to CO₂ and H₂O.The 2,4-dichlorophenol was mainly dechlorinated to produce byproducts such as phenol,which are then oxidized to organic acids and further oxidized to CO₂ and H₂O.