F-SiO2-embedded PLA-based superhydrophobic nanofiber membrane for highly efficient membrane distillation†

Abstract

Obtaining a superhydrophobic surface is key for constructing membrane distillation systems for desalination. Although perfluoroalkyl materials have been proven to be good candidates for membrane distillation, the lack of a friendly approach to treat waste perfluoroalkyl-based membranes has attracted significant concern. Herein, we propose a simple strategy for the preparation of superhydrophobic polylactic acid (PLA) nanofibre membranes. PLA nanofibres were coated with polydimethylsiloxane (PDMS) via coaxial electrostatic spinning technique, and 0.1% fluorine-modified silica (F-SiO₂) nanoparticles were embedded in the nanofibres to form nanoscale projections, which can increase roughness. Results showed that the coating of the low-surface-energy material PDMS and the nanoscale projections of F-SiO₂ endowed the membrane with excellent superhydrophobicity. The presence of the biodegradable material PLA and only 0.1% fluorine-containing substances made the membrane environment friendly. In addition, a large-pore-size high-flux support layer could maximize transmembrane vapor transfer while a small-pore-size high-rejection selective layer could avoid brine wetting and exhibited excellent salt rejection. The flux of the membrane reached 6.87 L m⁻² h⁻¹ and rejection was higher than 99%. Therefore, the PPF-AS membrane, as a superhydrophobic membrane, has wide potential for application in the field of MD.