Superhydrophobic Surface-Constructed Membrane Contactor with Hierarchical Lotus-Leaf-Like Interfaces for Efficient SO2 Capture.

An organic-inorganic polyvinylidene fluoride/polyvinylidene fluoride-silica (PVDF/PVDF-SiO2) mixed matrix membrane contactor is fabricated via a facile and efficient hydrophobic modification method. The solubility parameters of the PVDF particle are precisely regulated, the PVDF particles are blended with SiO2 nanoparticles to form PVDF-SiO2 suspension, and then the suspension is introduced onto the surface of the PVDF substrate by an in situ spin coating strategy. The PVDF particles are partly etched and incorporated to construct the adhesive PVDF-SiO2 core-shell layer on the PVDF substrate, which results in a more stable PVDF-SiO2 coating layer on the substrate. The surface structure is precisely regulated by changing the etching morphology of PVDF particles and amount of doped PVDF and SiO2 particles, forming an integrated porous PVDF-SiO2 layer and constructing hierarchical lotus-leaf-like interfaces. The resultant PVDF/PVDF-SiO2 membrane contactors display the relatively regular distribution of pore size with ∼420 nm and excellent hydrophobic property with a water contact angle of ∼158°, which noticeably lightens wetting phenomena of membrane contactors. The SO2 absorption fluxes can reach as high as 1.26 × 10-3 mol·m-2·s-1 using 0.625 M of ethanolamine (EA) as liquid absorbent. The high stability of the SO2 absorption flux test indicates the excellent interface compatibility between the PVDF-SiO2 coating layer and the PVDF substrate. The versatile organic-inorganic layer exhibits super hydrophobic property, which prevents wetting of membrane pores. In addition, the membrane mass transfer resistance (H/Km) and membrane phase transfer coefficient (Km) are explored.