Biomimetic preparation of polycaprolactone membrane with hierarchical structure as high efficient oil-water separator
The superhydrophobic, superoleophilic and eco-friendly polycaprolactone composite (PCLC) membrane with hierarchical microspheres structure was developed by alternated electrospinning/electrospraying technology. The PCLC membrane was subtly designed with two parts to imitate the lotus leaf structure: low surface energy SiO2 nanoparticles on the surface of PCL smooth microspheres (PCLM) imitated the hydrophobic bio-wax of the lotus leaf surface, and PCL porous microspheres (PCLM-porous) imitated the surface nano-protrusions of lotus leaf. The average size of the potholes on the PCLM-porous surface was only about 300 nm. The combination of small size potholes and the hierarchical structure of PCLC and SiO2 nanoparticles contributed to the superhydrophobicity and superoleophilicity of PCLC membrane. The water contact angle (WCA) of PCLC could reach 162.0 ± 1.5°. Compared with the PCLM-porous (WCA = 148.9 ± 1.2°) and 4% SiO2 nanoparticles on PCLM (WCA = 158.6 ± 2.3°) membranes, the PCLC membrane not only showed higher superhydrophobicity, but also ultra-high oil-water separation efficiency, oil flux and stability. Most importantly, the PCLC exhibited excellent oil adsorption performance for four kinds of oil with different densities, and the separation efficiencie still kept ultrahigh (> 99.93%) even after 10 cycle memsurments. This innovative work may enlighten an effective strategy for the design of biomimetic biopolymer, which can exploit the promising applications in the field of eco-friendly separator.