A novel silver / activated - polyvinylidene fluoride - polydimethyl siloxane hydrophilic-hydrophobic Janus membrane for vacuum membrane distillation and its anti-oil-fouling ability

In the membrane distillation process, the anti-fouling ability of the membranes is one of the main factors that affect the use of the membranes. In this paper, the Silver/Polyvinylidene fluoride - Polydimethyl siloxane (Ag/PVDF-PDMS) hydrophilic-hydrophobic Janus composite membrane was prepared by chemical reduction method to construct the underwater oleophobic silver layer on the surface of the hydrophobic Polyvinylidene fluoride - Polydimethyl siloxane (PVDF-PDMS) membrane, the silver layer can enhance oil resistance and increase membrane flux. To improve the adhesion between the silver layer and the substrate, the PVDF-PDMS membrane was activated by palladium, and then also by chemical reduction method, the Silver/Activated - Polyvinylidene fluoride - Polydimethyl siloxane (Ag/a-PVDF-PDMS) Janus composite membrane was produced. The properties of the membranes were systematically studied by scanning electron microscope (SEM), X-ray diffractometry (XRD), mechanical properties, contact angle (CA) and vacuum membrane distillation experiments. Compared with PVDF-PDMS and Ag/PVDF-PDMS membranes, Ag/a-PVDF-PDMS Janus composite membrane is better in mechanical property, underwater oleophobic performance and long-term operation stability, after vacuum membrane distillation treatment of crude oil/NaCl emulsion for 10 h, the flux recovery rate could arrive at 85%. This composite membrane will have huge application potential in seawater desalination and sewage treatment.