防污膜表面改性.pptx

Surface Modifications for Antifouling Membranes 第1页/共9页BackgroundModification method problemdefinitionandtypescause reasons第2页/共9页Backgroundvfouling=deposition vtypes particles,colloids,macromolecules,salts,etc.Temporary:the initial flux can be restored by washing the membrane or by applyingback-pressuresPermanent:cannot be restored第3页/共9页vcause:the interaction between the membrane surface and the foulants.(inorganic,organic,and biological substances in many different forms)第4页/共9页vreasons:The foulants will chemically degrade the membrane material,destroy of membrane structure.Fouling,at the membrane surface or inside the pore at the pore wall,reduces the membrane flux.periodical washing with chemicals,such as sodium hypochlorite solution,will result in the simultaneous degradation of the membrane materials lifetime.the skin layer or top surface layer plays the vital role in the separation process by membrane,which is essentially a surface phenomenon第5页/共9页Modification methodTo some extent,selection of an appropriate membrane,pretreatment of the process fluid,adjustment of operating design and conditions are all known to control fouling 第6页/共9页increase hydrophilicity.because protein and many other foulants are hydrophobic in natureelectrically charged which significantly reduces the scale-formationsurface roughness It is believed that the membrane fouling with particulate substance is enhanced by an increase in the surface roughness第7页/共9页 problemvThe simultaneous changes in the other parameters,when one of the parameters is changed,make the study of membrane fouling even more difficult.vhow much the surface modification can contribute to the fouling reduction,Once the deposition of foulants has taken place,the surface modification is no longer effective to prevent fouling第8页/共9页第9页/共9页