Bio-inspired method for preparation of multiwall carbon nanotubes decorated superhydrophilic poly(vinylidene fluoride) membrane for oil/water emulsion separation

The intrinsic hydrophobicity of polyvinylidene fluoride (PVDF) membrane impedes its application in the field of water treatment. In this work, hydrophilic modification of PVDF membrane is processed by a mussel-inspired method. Multi-wall carbon nanotubes (MWCNTs) were functionalized by grafting 3-aminopropyltriethoxysilane (APTES) firstly, and then they were directly decorated on PVDF membrane surface by dopamine copolymerizes. Energy dispersive X-ray spectrometry (EDX) mapping results exhibited that functionalized MWCNTs were well dispersed in the membrane matrix. The novel membranes turned from a hydrophobic state to superhydrophilic state (completely wetted in air within only 1 s). Besides, these provide modified membranes could be applied to separate different kinds of oil-in-water emulsions with high permeate flux (about 900 L/m2 h under 0.09 MPa) and ultrahigh oil rejection ratio (nearly 99%). More importantly, the as-prepared superhydrophilic PVDF membranes showed durable oil-fouling repellency, which could be easily recycled with a recovery of flux ratio up to 90%. In general, this bio-inspired modification might provide a new method for the preparation of superhydrophilic PVDF membrane and be very promising for application on oil/water emulsion separation.