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Effect of Ammonia as an Inert Solvent on Structure and Separation Performance for Oil/Water Mixtures of PVDF Porous Membranes

Porous polyvinylidene fluoride (PVDF) membranes were prepared from PVDF and N-methyl-2-pyrrolidone (NMP) solution system using immersion precipitation phase inversion technique with ammonia as an inert solvent additive. The effects of ammonia amount on pore size, surface morphology, crystallinity, hydrophobic property, oil uptake and water-oil separation performance of the membranes were investigated. It was found that all membranes had an interpenetrating porous structure. The increase of ammonia amount led to significant variations in morphology. Lots of tiny apophysis formed on the membrane surface, pore size deceased, and pore density increased with the increase of ammonia amount. The crystallinity decreased with increasing ammonia amount, and hydrophobic property was improved. The membrane showed high oil uptake and effective separation function of oil-water mixture.