Research On The Mechanism Of Pre-oxidation-MIEX Combined Use To Control Ultrafiltration Membrane Fouling In Water Purification Process

Ultrafiltration is the core of the third generation drinking water treatment technology.Membrane pollution has always been an important issue limiting its application.Pre-membrane pretreatment is one of the effective methods to improve the quality of ultrafiltration water and slow down membrane pollution.As two new and efficient water purification technologies.MIEXadsorption and K₂Fe O₄pre-oxidation have received more and more attention.However,the difference between the two in controlling membrane fouling when combined with ultrafiltration,and the mitigation between them Whether the membrane fouling has a synergistic effect is still lacking systematic research.In this experiment,the micro-polluted source water was simulated by diluting the lake water of Tian Gong University to investigate the mitigating effect of MIEX adsorption and K₂Fe O₄pre-oxidation on membrane pollution,and the synergy between the two pretreatment technologies in controlling ultrafiltration membrane pollution.The mechanism of membrane pollution mitigation is discussed from the aspects of filter cake layer structure,total organic matter reduction,hydrophilicity and hydrophobicity,and molecular scale.The research results show that K₂Fe O₄-MIEX-UF has the most significant effect on controlling membrane fouling compared to the other three processes in the continuous five-cycle operation experiment.The irreversible K₂Fe O₄-MIEX-UF process at the end of the five-cycle filtration The cumulative pollution rate was 0.0002min^-1,which was 89.4%,50.0%,and 68.8%lower than that of UF,MIEX-UF,and K₂Fe O₄-UF,respectively.Compared with UF alone,the reversible resistance was reduced by 68.4%,and the irreversible resistance was reduced by 90.1%,which were significantly higher than the membrane fouling control effect when MIEX and K₂Fe O₄were used alone.In terms of effluent water quality,the removal rate of DOC by the K₂Fe O₄-MIEX-UF process reached 89.1%,the removal rate of aromatic compounds(UV₂₅₄)reached 92.6%,and the removal ability of the five types of organic compounds was significantly improved,which improved MIEX and The problem that K₂Fe O₄has a low ability to remove certain kinds of organic compounds when it is separately pretreated.Studies on the mechanism of membrane fouling control show that K₂Fe O₄pre-oxidation will generate Fe?OH?₃microflocculants with a particle size of about 10times the particle size of organic matter in raw water.Therefore,compared with UF alone,the membrane cake layer in the K₂Fe O₄-UF process is more porous and permeable.In the K₂Fe O₄-MIEX-UF combined process,the micro-magnetic field of MIEX will further promote the magnetic flocculation effect of iron floes and form larger-scale floc particles.Resin particles iron salt flocs and organic matter together form a filter cake layer on the membrane surface.The presence of iron flocs makes up the gap between resin particles and forms a more porous and permeable filter cake layer on the membrane surface.Microscopic interface force analysis shows that the stronger interfacial force between"pollutant-MIEX"and"pollutant-floc"promotes the pollutant compared to the pollutant-membrane and pollutant-pollutant interface forces.Tighter binding on resin particles and floc particles,thereby weakening the binding force between the pollutants and the membrane surface,which is beneficial to the removal of the filter cake layer during backwashing.In addition,the combined pretreatment of K₂Fe O₄-MIEX not only greatly improves the removal of total organic matter in water,but also has a synergistic effect in terms of hydrophilic and hydrophobic components and molecular scales,which is conducive to the comprehensive removal of various membrane pollutants.