The Preparation Of Cu/Fe Doped Al-MCM-41 Catalyst And The Application In The Printing And Dyeing Wastewater Treatment

The printing and dyeing wastewater are regarding as a difficult problem of wastewater treatment at home and abroad due to the large emission amounts and high concentration of organic compounds.The hydroxyl radical produced by Fenton oxidation process has the powerful oxidation ability to degrade organic compounds which are widely used in the area of printing and dyeing wastewater treatment.However,the homogeneous Fenton system is efficient only in the strong acid condition and it is very easy to produce iron-containing sludge.Hence,synthesizing efficient,low pH-dependence and stable heterogeneous Fenton catalysts are significant to the treatment of the printing and dyeing wastewater.In this thesis,seven MCM-41(mesoporous molecular sieve of M41S family)heterogeneous Fenton catalysts with different metal doping amounts were successfully synthesized by the sol-gel method and one catalyst was synthesized by the impregnation method as a comparison.The FT-IR results showed that the metal of catalysts synthesized by the sol-gel method was introduced into the framework of MCM-41 and formed the Metal-O-Si band.The metal of catalysts synthesized by the impregnation method was supported on the surface of MCM-41.The XRD results showed that the metal of catalysts synthesized by the sol-gel method was highly dispersed and all catalysts synthesized by the sol-gel method except M2-0 persevered the mesoporous structure of MCM-41.The order of the mesoporous structure of catalysts decreased with the increase of the metal introduction amounts.SEM and BET results showed that the particles became smaller and heavily agglomerated into nanomicrospheres resulting in the decrease of the specific surface area with the increase of the metal introduction amounts.The results of XPS demonstrate that the valence of Cu and Fe on the surface of M2 were Cu2+,Cu+,Fe2+ and Fe3+ which were beneficial to the redox cycle of Cu+/Cu2+and Fe2+/Fe3+.The above analyzing results showed that the as-synthesized catalysts possessed a high specific surface area which enhanced the mass transfer and the dispersity of active metals.Doping metal was better than supporting metal to decrease the leaching amounts of metal.Furthermore,the moderate doping metal amounts were beneficial to maintain the stability of the mesoporous structure.Aiming to improve the activity of the catalysts under neutral pH conditions,the incorporation amounts of Cu were increased under the precondition that the mesoporous structure of catalysts was not destroyed.Rhodamine B(RhB)was chosen as the target pollutant to study the effect of the doping molar ratio of Cu versus Fe and the way of introducing metal(doping and supporting)on the activity and stability of the catalysts.The experimental results showed that the catalyst M2 synthesized by the sol-gel method with the molar ration(Cu versus Fe)of 2 performed best at the neutral pH conditions.After 50 minutes'reaction,the decoloration efficiency and the COD removal rate of 400 mg/L RhB at neutral pH reached 97.3%and 43.0%,respectively.The catalysts M2 were chosen to study the absorption mechanism and reaction mechanism of RhB.The experimental results showed that the absorption and degradation of RhB were fitted well with the Freundlich model,the pseudo-secondorder adsorption kinetic model and the first-order kinetics model.And·OH took a major role in RhB degradation.M2 performed good at degrading dyes with different structures(Methyl Orange,Methylene Blue and Congo Red),the decoloration efficiency was all above 85.0%after 50 minutes' reaction indicating that M2 could degrade different kinds of dyes.To study the efficiency of M2 on real wastewater treatment,the effluent water of the secondary setting tank after A/O process produced by a Henan's printing and dyeing company was treated by M2.A three-stage series intermittent process was designed as the depth treatment section and the dosage of the catalysts M2 and H2O2 in each stage was optimized.At the optimal conditions,after three-stage treatment,the COD of the wastewater decreased from 280 mg/L to 55.4 mg/L,the COD abatement rate was 80.2%.The properties of the effluent water were stable after running 7 times.The qualities(pH,BOD5,COD,ammonia nitrogen,aniline and chromaticity)of the effluent water were significantly enhanced indicating that this process had great application prospect.