Degradation Of Nitrobenzene By High-gravity Intensified Heterogeneous Catalytic Ozonation With Supported ZSM-5 Catalysts

Nitrobenzene containing wastewater is great threat to human health and ecological environment,and the heterogeneous catalytic ozone method has the characteristics of fast reaction speed,high degradation efficiency and no secondary pollution.Metal oxide supported ZSM-5 catalyst has been widely studied in the field of organic wastewater treatment as a highly efficient catalyst for ozone oxidation.However,there are still some problems such as low volume mass transfer coefficient of ozone liquid phase and difficult recovery of powdered catalyst in the process of using supported ZSM-5 catalyst to degrade nitrobenzene wastewater.The supported catalyst was prepared with spherical support to make its packing functional.Meanwhile,based on the characteristics of enhanced mass transfer and micro-mixing by high gravity technology,the idea of enhanced heterogeneous catalytic ozonation of nitrobenzene in wastewater by high gravity supported ZSM-5 was proposed in this paper.With nitrobenzene as the research object,high gravity rotating packed bed（RPB）as the reactor,the preparation of supported Mn-Fe O_X/ZSM-5 catalyst as the packing to degrade of nitrobenzene in wastewater.For catalyst preparation process of the preparation time is long and uneven active component,the supported Mn-Fe Ox/ZSM-5 catalyst was prepared by high gravity method.The effects of technological parameters on the removal of nitrobenzene,the performance,reuse rate and degradation mechanism of the prepared supported Mn-Fe Ox/ZSM-5 catalyst were systematically studied.（1）Single-component Mn,Fe,Cu,Ce oxide supported ZSM-5 catalyst and two-component Mn doped Fe,Ce,Cu oxide supported ZSM-5 catalyst were prepared by incipient wetness impregnation method,and their catalytic performance was investigated.ZSM-5supported Mn oxide had the best catalytic effect,and TOC removal efficiency reached 59.0%.In this paper,density functional theory was used to simulate the adsorption energy.The results show that ozone is adsorbed on the supported ZSM-5 to form oxygen atoms on the surface,and surface peroxide is formed when Mn-Fe O_X/ZSM-5 is adsorbed on the surface.Mn-Fe O_X/ZSM-5 has the best effect,which is consistent with the experimental results.（2）Mn-Fe O_X/ZSM-5 was used as the packing of the rotating packed bed,and the idea of Mn-Fe O_X/ZSM-5 heterogeneous catalytic ozone degradation of nitrobenzene in wastewater was proposed based on the fact that the high-gravity field could enhance the mass transfer characteristics.The effects of different operating conditions on the total organic carbon（TOC）removal efficiency of Mn-Fe O_X/ZSM-5 in the rotating packed bed at room temperature were studied.The removal efficiency of bubbling reactor was compared.The results show that whenβis 20,initial O₃ concentration is 25 mg/L,Q_L is 60 L/h,initial p H is 6,and reaction time is 40min,TOC removal efficiency can reach 72.6%.Compared with the aeration reactor（BR）,the TOC removal efficiency of RPB increased by 33.5%,and·OH was verified by adding the free radical trapping agent tert-butanol and electron paramagnetic resonance technology.In conclusion,the enhancement of Mn-Fe O_X/ZSM-5 heterogeneous catalytic ozone by high gravity can effectively improve the degradation effect of organic wastewater.（3）Due to the long preparation time and uneven distribution of active components of the supported catalysts prepared by traditional methods,the idea of using the high gravity method to prepare ZSM-5 supported Mn and Fe oxides heterogeneous catalyst（Mn-Fe O_X/ZSM-5）was proposed based on the characteristics of enhanced mass transfer and micro-mixing.The effects of different preparation conditions on the removal efficiency of nitrobenzene and total organic carbon（TOC）in high-gravity field were studied.The stability of Mn-Fe O_X/ZSM-5and the loss of its active component were investigated.The mechanism of Mn-Fe O_X/ZSM-5catalyzed ozonation of nitrobenzene was investigated.The results show that Mn-Fe O_X/ZSM-5 metal oxides prepared by high gravity method have good dispersibility.When the concentration of impregnation solution is 0.3 mol/L,the high gravity factorβis 30,and the flow rate of impregnation solution is 60 L/h,the catalytic effect of Mn-Fe O_X/ZSM-5 is the best,and the TOC removal efficiency can reach 87.5%after 25 min.After repeated use for 5times,TOC removal efficiency is above 80%.The preparation time and the loss of active components can be greatly reduced by using high gravity method.The catalytic degradation of nitrobenzene by ozone follows the principle of free radicals.