Preventing Wetting in Membrane Distillation: Membrane Fabrication and Wetting Detection & Control System Development

Description

Low surface energy materials and lotus-leaf-inspired surfaces have motivated the development of membrane non-wettability and superhydrophobic properties for membrane distillation (MD). Lotus leaves achieve high contact angles through a combination of coated surface and hierarchal micro/nano double reentrant structures, becoming a catalyst for surface modifications. Long-chain fluorocarbon which mimics the anti-wetting properties of lotus leaves has been used for chemical functionalization of MD membranes. However, the potential dangers of bioaccumulation and toxicity from their use have recently put them under the spotlight, underscoring the need for developing safer alternative materials that are environmentally benign. In this respect, hierarchical micro/nanostructures with nonfluorinated membrane surface modification and branched short-chain fluorocarbon can provide a muchneeded environmentally safe replacement solution.Over the past few years, we have been studying the fabrication of anti-wetting membranes for MD using surface coatings as well as micro/nano double layered surfaces and re-entrant structures. Recently, we have started developing short-chain fluorinated coatings and micropatterning techniques, which have been of increasing interest in the field of material science, to fabricate a new generation of MD membranes. Herein, we propose to study three scientific aspects of the improved anti-wetting membrane and their impacts on MD operations.First, we propose to use highly branched short chain perfluoroalkyl silanes in MD membrane surface modification as an alternative to the long-chain fluorinated group. Specifically, we will use fluorous silanes containing branched nonafluoro-tert-butoxy groups. The fluorous sol gel will be carefully analysed by Infra-red (IR) Spectrometry, Scanned Electron Microscope Energy Dispersion X-ray (SEM-EDX), and X-ray Photoelectron Spectroscopy (XPS) to determine the yield of the coupled product before its application in MD. Meanwhile, wWe will architecture the desired micro/nano structure of MD membranes using surface micropatterning to create doubly re-entrant cavities to make an omniphobic membrane. Second, we will build a wetting detection system to conduct a systemic study of the wetting mechanism. Finally, membrane restoration techniques in long-term MD operations will be carried out.Membrane wetting is one of the major issues that hamper MD’s long-term successful performance and industrial applications, yet, MD research that incorporates a detection system for membrane wetting and restoration is scarce. Therefore, the successful implementation of this proposal will provide a valuable systemic study on the effects of surface wetting in the field of MD membranes and invigorate further research in this direction, bringing MD commercialization even closer within our reach.