Preparation Of Modified Ceramic Membrane And Its Performance Of Alleviating Membrane Fouling Through Catalyzing Pms In-situ Oxidation

Membrane fouling is a main obstacle to the application of low pressure-driven membrane process.Advanced oxidation process combined with membrane filtration is an effective way to control membrane fouling.The preparation of modified ceramic membranes with heterogenous catalysts,newly prepaed MnFe₂O₄,Fe₂O₃ and commercial MnO₂ and their performance of in-situ catalyzing peroxymonosulfate combined with low pressure-drive ceramic membrane filtration on the control of membrane fouling were systemmatically studied for the first time.MnFe₂O₄ and Fe₂O₃ were prepared on the basis of existing researches,and MnO₂was screened to prepare materials for ceramic membrane modification.XRD,FTIR,Zeta potential test were conducted to characterize structure and properties of the materials,isothermal N₂ adsorption-desorption test was used to analyze the surface area and pore volume of them.The modification of preparation method of MnFe₂O₄ and Fe₂O₃ made their surface area and pore volume larger,which is conducive to improving the activation efficiency of the corresopnding modified ceramic membrane.A high pressure was applied to drive commercial ceramic membranes to filtrate suspension of MnFe₂O₄,Fe₂O₃ and MnO₂ respectively,materials used for membrane modification was deposited evenly on the surface of ceramic membranes,the newly prepared ceramic membrane was dried and then sintered with 500^oC to make sure a stable connection between the membrane surface and the deposited materials was formed.Low pressure-driven membrane process was operated to investgate the performance of the modified ceramic membranes,SA,BSA,HA and their mixed solution were recieved as simulation of NOM fractions.The comparison of specific flux and TOC interception rate between commercial ceramic membrane and modified ceramic membranes showed that surface modification of ceramic membrane had minor influence on alleviating the decline of specific flux,and retention rate of TOC was lightly increased as a result of adsorption of NOM by the deposited materials.Materials deposited on the surface of ceramic membrane,namely MnFe₂O₄,Fe₂O₃and MnO₂ can act as kinds of heterogeous catalyst to activate the decomposition of PMS.Overall,in-situ oxidize NOM through free radicals generated from decomposition of PMS by the modified ceramic membranes was able to ease membrane fouling in a different degree.Properties of materials deposited and NOM fractions are major factors affecting effectiveness of membrane fouling control.PMS dosage at 0.5mM was optimal for the in-situ oxidation process.Free radical competition test was conducted to explore dominant reaction mechanism of catalyzing PMS in-situ oxidation,the result indicated that both·OH and SO₄^·-existed in the system.Surface morphology and roughness of ceramic membranes before and after filtering mixed solution of NOM fraction simulation were characterised by SEM and AFM.Solute of NOM retained by membrane covered membrane surface,so as to reduce the surface roughness.After filtering of NOM,the deposited materials were stripped off and characterized by FTIR,changes of locations of the characteristic absorption peak showed that intramolecular or intermolecular hydrogen bonding effect caused a red shift of the adsorption band.Intramolecular or intermolecular hydrogen bonding effect lead to a polymerization cross-linking between the retained solute and deposited materials,therefore intensifies membrane fouling.The machanism of membrane fouling formation and fouling control through catalyzing PMS in-situ oxidation was analyzed.NOM adsorption and retention by membrane surface is the mian reason for the formation of membrane fouling.Membrane fouling formation of modefied ceramic membrane was mainly dominated by the standard blocking model,moreover intermediate blocking and cake filtration modle contributed to fouling formation.In-situ oxidation of NOM through catalyzing PMS increased the ratio of low molecular weight NOM,as a result membrane fouling was douminated by the standard blocking modle.Membrane pores adsorp low molecular weight NOM first,and then the pore was narrowed,as a result NOM with a relatively higher molecular will be intercepted,membrane fouling started to evolution and finally came into being.