Pine powders-coated PVDF multifunctional membrane for highly efficient switchable oil/water emulsions separation and dyes adsorption

Faced with the severe challenge of water resources contaminated by oily organic solvents and dyes, water pollution has caught the attention of the world. Materials with special wettability to deal with oily pollution have been successively reported, but the multifunctional materials with separation multi-type oil/water emulsions and water-soluble dyes are still rare. In this work, a multifunctional separation membrane was prepared through depositing pine powders (PPs) onto the polyvinylidene fluoride (PVDF) membrane. The as-prepared membrane can achieve switchable wettability between underwater superoleophobicity and underoil superhydrophobicity, even in the harsh environments (acid, alkali and salt environments), to separate at least 12 types of surfactant-stabilized oil/water emulsions (oil-in-water and water-in-water) with separation efficiency as high as 99.7%. After 500 times bend tested, the membrane material did not have any cracks, showing excellent mechanical robustness. Moreover, the separation membrane can also adsorb at least 3 types of anionic and cationic dyes (Methylene blue, Congo red and crystal violet) from waste water with adsorption efficiency still up 99.75% even multiple cycles. Therefore, this economy membrane-making strategy can promote the extensive development of multifunctional superwetting materials and open up new prospects for the preparation of novel membrane materials.