Nanocoated amphiphobic membrane for flux enhancement and comprehensive anti-fouling performance in direct contact membrane distillation

Abstract

Membrane distillation, which can utilize low grade energy, has attracted significant attention recently. However, membrane fouling is a big issue impeding its development and industrialization. Hence, it is essential to prepare amphiphobic membrane for comprehensive anti-fouling performance. Herein, a facile and biomimetic method is explored to design amphiphobic surface with special structure and controllable wettability. Commercial polyvinylidene fluoride (PVDF) was primarily functionalized with polydopamine (PDA) coatings and then nanoscale roughness was introduced on the membrane surface, followed by the fluorination of 1H,1H,2H,2H-perfluorodecanethiol. It is revealed that the amphiphobic property can be accurately controlled by controlling the dosage of Ag+. When the concentration of Ag+ is 300 mM, the water and oil contact angle of the optimal membrane can achieve 167.6 ± 0.27° and 136.9 ± 0.4°, respectively, while the water sliding angle is only 3 ± 0.1°, which demonstrates prominent superhydrophobicity and oleophobicity. Furthermore, the amphiphobic membrane exhibits excellent chemical and thermal stability under harsh conditions as well as outstanding comprehensive anti-fouling capacity with higher flux and excellent salt rejection in the long-term direct contact membrane distillation (DCMD) experiments, which shows promising potentials for application in the field of membrane distillation.