Ultrafiltration membrane materials

There are many materials that can be used to make ultrafiltration membranes, including: polyvinylidene fluoride (PVDF), polysulfone (PS), polyether sulfone (PES), polyethylene (PE), polypropylene (PP), polyacrylonitrile (PAN), polyvinyl chloride (PVC), etc. These materials have been used commercially. Films made of different materials have different properties. The evaluation of a film material from the perspective of water treatment application mainly depends on its chemical stability, mechanical strength, hydrophilicity and so on.

Chemical stability

Chemical stability determines whether the film can be used in a particular environment and its service life. In general water treatment applications, it is usually investigated whether it will occur hydrolysis, resistance to microbial degradation, acid resistance, alkali resistance, oxidation resistance and other properties of fungicides.

In the usual water environment application, the membrane material should not be hydrolyzed, and not be degraded by microorganisms, which is the basic requirement for the membrane material. Early membrane materials (such as acetate fiber, polyvinyl alcohol), due to easy hydrolysis, can only be used in a narrow pH range, short life, has been basically not used in the field of water treatment filter membrane. The above-mentioned membrane materials, which are widely used today, have good resistance to hydrolysis and biodegradation.

The properties of acid, alkali and oxidant resistance of the membrane material directly affect the method that can be used for membrane cleaning, and the cleaning method directly affects the recovery of membrane flux after contamination. Under normal circumstances, the chemical agents used to clean the film are acid (hydrochloric acid, citric acid, oxalic acid, etc.), alkali (NaOH, KOH, etc.), oxidant (sodium hypochlorite, hydrogen peroxide, peracetic acid, etc.). In terms of acid and alkali resistance, the above-mentioned various membrane materials have good performance. The antioxidant resistance of polyvinylidene fluoride (PVDF) is more prominent than that of other membrane materials. The removal of microbial pollution usually uses strong oxidizing fungicides such as sodium hypochlorite (NaClO), so in water treatment prone to microbial pollution (such as surface water purification, water reuse, sewage treatment), PVDF materials are more suitable than other materials.