Research On Degradation Of Typical Enviro-nmental Hormones In Water In A Dielectric Barrier Discharge Plasma System Combined With RGO-WO₃ Composite Catalyst

Environmental hormones are exogenous chemicals which can affect the normal hormone levels in human and animal bodies.Environmental hormones in water environment are stable and undegradable by the traditional water treatment technologies.In this study,the dielectric barrier discharge plasma（DBDP）and the reduced graphene oxide（r GO）-WO₃composite catalysts were combined together to degrade the typical environmental hormones in water.The synergistic process could improve the energy utilization efficiency of the DBDP as well as realize the high-efficient degradation of the environmental hormone pollutants.Firstly,preparing and characterizing of the WO₃and r GO-WO₃nanocomposites,and then establishing the combined water treatment system of the DBDP and the composite catalyst,investigating the effect of addition amount and preparation parameters of the composite catalyst on the bisphenol A（BPA）degradation and determining the optimal addition condition and catalyst preparation parameters of the catalyst.Secondly,choosing dimethyl phthalate（DMP）as the target pollutant,investigating the influence of solution and carrier gas parameters on the DMP degradation.Finally,analyzing the corresponding mechanism.The main results are summarized as follows:（1）The DBDP/r GO-WO₃system was established to investigate the influence of the mass ratio of graphene oxide（GO）to Na₂WO₄,reaction time,reaction temperature on the BPA degradation.The obtained results showed that the optimal dosage of the composite catalyst was 40 mg/L;the optimal preparation parameters of the composite catalyst were:5:1000 mass ratio of GO to Na₂WO₄,18 h reaction time,reaction at 120℃.Under the condition,the degradation rate of BPA is 83.3%after 60minutes of reaction in the DBDP/r GO-WO₃system,which is 19.6%higher than that of the single DBDP system,19.1%higher than that of DBDP/WO₃,and 17.2%higher than that of DBDP/GO.After four cycles of using experiments,the r GO-WO₃remained a relative stable catalytic effect and structure of the composite catalyst were basically stable.（2）Choosing the DMP as the target pollutant,investigate the influence of solution parameters（initial concentration,initial p H value and conductivity）and carrier gas parameters（carrier gas type and amount）on the DMP degradation.The obtained results showed that the r GO-WO₃composite had a catalytic effect under various operating parameters;the lower initial concentration（10 mg/L）was beneficial to the DMP degradation;the initial conductivity of the solution had little effect on the degradation;compared with the acidic and alkaline solution conditions,neutral conditions are more conducive to the DMP degradation;the degradation rate of DMP in the DBDP/r GO-WO₃system with oxygen as the carrier gas could reach 99.0%at15 min reaction time,which was much higher than that of the reaction system with air and nitrogen as carrier gas;the optimal air bubbling rate was 0.5 L/min.（3）The mechanism analysis results showed that the mineralization and biodegradability of the BPA and DMP solutions were enhanced by adding r GO-WO₃into the DBDP system;the corresponding O₃concentration in the reaction system decreased,the H₂O₂concentration increased;the spectral analysis results proved that the reactive oxygen species（ROS）and reactive nitrogen species（RNS）were effective species for the pollutants degradation;the p H value of the target solution decreased while the solution conductivity increased during the degradation process;the intermediates of the BPA degradation included 4-cumylphenol,4-isopropenylphenol,tert-butylbenzene,1,4-benzene diphenol,p-isopropyl toluene,phenylacetone and fumaric acid etc.;the intermediates produced by DMP degradation included phthalic acid,phthalic acid monoester,succinic acid,terephthalic acid,glutaric acid etc..For the catalytic effect of the r GO-WO₃in the DBDP system,it could be speculated as follows:the light effect in the DBDP system could induce WO₃to form electron-hole pairs,and the O₃produced by the DBDP system itself could trap photo-generated electrons to generate·OH,the introduction of graphene could inhibit the combination of electron-hole pairs and then promoted the generation of·OH,the effect of the DBDP on the organic compounds degradation was finally improved.