Degradation Of Organic Matter In Reverse Osmosis Concentrate By Heterogeneous E-fentons Technology

As a potential water resource,the effluents of urban sewage can not only be used as reclaimed water,but also as industrial production water and supplemental water of drinking water source after treated by reverse osmosis(RO)techniques.owever,the concentrated water is about 20% ~ 25% of the RO feed water with the pollutants concentrated 4~5 times,which is comprised of many organic and inorganic pollutants and is characterized as complicated composition,and strong refractory.Therefore,advanced treatment of the concentrated water are becoming increasingly significant..Heterogeneous Electro-Fenton(E-Fenton)method is a new technology for concentrated water treatment,which received increasing attention in recent years.It has a significant effect on degradation organic pollutant of the RO concentrate water due to its high salinity and strong conductivity.In this paper,the catalyst of Mn-Cu bimetallic oxides supported aluminum-containing MCM-41,was synthesized by coprecipitation method.It was used for degrading simulated RO concentrate in the heterogeneous Electro-Fenton process.The CODCr removal rate of the simulated RO concentrate was acted as the evaluation index.The main factors affecting the performance of the catalysts were investigated,and the characterization of catalysts were analyzed.The influence of related factors on treatment of H2O2 and CODCr removal rate by CF(Carbon Felt)-Pt E-Fenton system through the single factor experiment was examined,the degradation mechanism was analyzed and researched by following aspects: contrast experiment of different process,kinetics of fitting,stability test of the samples,the mechanism analysis of different metal species.The conclusions can be drawn as following:(1)Four catalysts of M1(MCM-41),M2(Mn/MCM-41)load,load M3(MnCu/MCM-41),M4(Mn-Cu/MCM-41-Al)were prepared by co-precipitation method.Among all,M3 and M4 showed the highest catalytic activity,moreover,the catalyst modified by aluminum(M4)showed better stability than other catalysts,which could significantly reduce the leaching of metal ions.The optimal preparation conditions of M4 catalyst were calcinated at 550 ? for 6 h with the dosage of manganese ions and copper ions of 0.3 mmol/L.The prepared catalysts were characterized by transmission electron microscope(TEM),X-ray diffraction(XRD),and BET.Results showed that all the samples are ordered two dimensional six square mesoporous structure,and the metal particles are dispersed uniformly in the silicon dioxide frame.The specific surface area of the catalyst are decreased with increasing the addition of metal species.(2)The production of H2O2 in the CF-Pt-Fenton system were investigated.The highest H2O2 production of 105mg/L was obtained under the optimal conditions with Na2SO4 solution of 0.1mol/L,current density of 3.5 m A/cm2,oxygen volume of 0.3 m3/L,p H 3,and reaction time of 180 min.The electrolyte type?current density and oxygen flux have great influence on the production of H2O2 of the system.The production of H2O2 in the CF-Pt E-Fenton system is stable,so the system has a good application prospect in the production of H2O2 and degradation of organic pollutants.(3)In order to investigate the degradation of organic compounds in heterogeneous E-Fenton system,the removal efficiency of organic compounds(humic acids)under seven systems was discussed.The experimental results show that the removal of humic acid by the heterogeneous E-Fenton system has the effect of adsorption,electrochemical oxidation and Fenton oxidation,and the Fenton oxidation is dominant.The activity of the catalyst M4 is high,so the E-Fenton technology is more efficient than the other oxidation technologies.(4)M4 as a catalyst,the treatment of simulated RO concentration solution by CF-Pt E-Fenton system through single factor experiment were investigated,the optimum conditions are showed as follows:: p H=6,catalyst M4 dosage 0.5g/L,current density 3.5 m A/cm2,the oxygen volume 0.3 m3/L,reaction time 60 min,the CODCr removal rate up to 90%,the residual concentration of CODCr is 15mg/L,and general current efficiency(GCE)is 43%.In the case of the same reaction conditions,the lower salt content(500~1000 mg/L)in the simulated RO concentrate is helpful to the removal of CODCr when the salt content is between 500~2000 mg/L.In the wider range of p H(3~7),the degradation of humic acid in the CF-Pt E-Fenton system was stable,and the removal rate of CODCr was around 90%.The system has good removal effect on organic matter under near neutral conditions.(5)The reaction mechanism of the heterogeneous E-Fenton is analyzed and investigated.The mechanism of degradation of humic acid by heterogeneous EFenton system was discussed,and the catalytic oxidation mechanism of M4(MnCu/MCM-41-Al)catalyst was established.The kinetic of fitting on the degradation of humic acid in the heterogeneous E-Fenton system show that have the quasi first-order kinetics.It was found that copper and manganese could obviously improve the activity of the catalyst.The addition of aluminum almost has no effect,but it can stabilize the metal and reduce the leaching of metal ions.The stability of the catalyst M4 was tested.After repeated use of three times,the degradation rate of humic acid still can reach around 80%,and the leached metal ions were less.