Development Of Superhydrophobic PVDF-PDMS-SiO~2 Hollow Fiber Composite Membrane For Membrane Distillation

Membrane distillation is a membrane separation process using a hydrophobic membrane as a medium and has been widely concerned in the field of water treatment.In membrane distillation,two factors constrain its development,which are the wettability and hydrophobic stability of the separation membrane,so the development of long-lasting hydrophobic and anti-wetting membranes has become a hot topic in membrane distillation.In this paper,super-hydrophobic PVDF hollow fiber composite membranes were prepared by surface coating method and sol-gel method and applied to membrane distillation(MD)process to verify their anti-wetting properties.First,through the reaction of methyltriethoxysilane(MTES),polydimethylsiloxane(PDMS)and catalyst dibutyltin dilaurate(DBTL)on the membrane surface,a dense and hydrophobic layer was formed on PVDF membrane surface.The effects of the reaction solution composition and reaction parameters on the structure and performance of the membranes were studied.By this means,PDMS/PVDF composite hydrophobic membranes with good anti-wetting property were obtained.The pure water contact angle of the composite membrane reached 130°.Owing to the dense and hydrophobic PDMS layer,the composite membrane worked more than 2 h in DCMD experiment for surfactant solution treatment,in which traditional PVDF membrane was fully wetted no more than 30 min.Then,based on the PVDF/PDMS composite membrane,it was further subjected to superhydrophobic modification.Then,a nano-SiO2 sol prepared by sol-gel method was applied and bound on top of the PDMS base layer to improve the roughness.To increase the durability of the increased membrane hydrophobicity,another PDMS layer was applied on top of the SiO2 layer.Finally,a PDMS-SiO2-PDMS "sandwich"superhydrophobic composite layer was successfully constructed on the membrane surface.The contact angle of composite membrane reached 152.5°.The stable MD operation time was enhanced up to 20 times or more of the PVDF original membrane.