Study On The Catalytic Mechanism And Dynamics Of The Catalytic Oxidation Regeneration Of Ni-High Temperature Oxygen Flow Modified Sepiolite

Catalytic oxidation regeneration of adsorbent by high temperature gas is a new method used to treat wastewater.However,its catalytic mechanism and dynamics of the regeneration process have nearly been reported.The studies were focused on the regeneration process of catalytic adsorbent prepared by Ni modified sepiolite under high temperature oxygen flow.Methylene blue was used as the target removal pollutant by the adsorbent.The main research contents and conclusions in this work are summarized as follows:1.Adsorption behavior of methylene blue on Ni modified sepiolite under high temperature oxygen flow was studied.Effects of temperature and adsorption time on adsorption were investigated.The results showed that the adsorption isotherm of methylene blue on Ni modified sepiolite matched Langmuir equation within the observed temperature and concentration ranges.The adsorption process was an endothermic adsorption.2.The Ni modified sepiolite was characterized with X-ray powder diffraction(XRD),scanning electron microscopy(SEM),thermo gravimetric(TG)technique and temperature programmed reduction(TPR).The results showed that Ni modified sepiolite improved oxidation activity of the adsorbent.NiO was identified in the presence of catalyst.Degradation temperature of methylene blue adsorbed on the Ni modified sepiolite was observed at 350℃ lower than that on the normal sepiolite at 400℃.Furthermore,Ni modified sepiolite showed a higher stability during the process of regeneration.3.The catalytic regeneration mechanism of Ni modified sepiolite under high temperature oxygen flow was studied.The results showed that Ni combined with sepiolite in the form of NiO play an important role in catalytic oxidation during the process of catalyst regeneration.In situ diffuse reflectance Fourier transform infrared spectroscopy(DRFTs)was used to investigate Ni modified sepiolite adsorbed methylene blue at 350℃.The results showed that C-H structure of the methylene blue broke at first after 1 minute.C=C and C=N structure borke after 3 minutes.The degradation of Methylene blue went further after 5 minutes.After 7 minutes,the regeneration process completed when Methylene blue degraded completely.4.Regeneration kinetics of Ni modified sepiolite under high temperature oxygen flow was studied.The effects of regeneration temperature and O2 concentrations on the regeneration process of Ni modified sepiolite in O2 atmosphere were investigated using thermogravimetric technique.The results showed that degradation of methylene blue initialized at regeneration temperature higher than 350℃.The regeneration rate of catalyst increased at higher regeneration temperature and O2 concentrations.The regeneration reaction order was confirmed to be the first order by using a homogeneous reaction model.Kinetics behavior of the regeneration reaction of modified sepiolite was investigated according to the equivalent particle model.The apparent activation energy of the chemical reaction and corresponding frequency factor were 101.20 kJ/mol and 4.85×104m/s,respectively.The apparent kinetics equation of the regeneration process is:-rA=exp(-12.172×103/T+10.789)·(1-x)·CO25.Based on the above research works,the regeneration process of the Ni modified sepiolite was analyzed according to the characteristics of catalytic oxidation regeneration under high temperature air flow.On the basis of the theory of mass transfer and chemical reaction dynamics theory,a spherical particle diffusion reaction model was established targeting on O2 as key component according to the material balance.The main model equation is:equation:Its initial condition is:t=0,cAs=CAd The boundary condition is:r=0,(?)CA/(?)r=0 r=R,-NA=kc(CAs)=ks(?)CA/(?)r|r=R...