Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique.

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Membrane technology is crucial for water treatment.
• Developing robust membranes for challenging wastewater is essential.
• Omniphobicity enhances membrane performance and durability.

Purpose of the Study:

• To fabricate omniphobic composite membranes using layer-by-layer assembly.
• To evaluate the performance of these membranes in air gap membrane distillation (AGMD).
• To assess their suitability for treating saline wastewater with low surface tension contaminants.

Main Methods:

• Layer-by-layer (LBL) assembly of silica aerogel (SiA) and perfluorodecyltriethoxysilane (FTCS) on a polyvinylidene fluoride membrane.
• Interconnection using poly(diallyldimethylammonium chloride) (PDDA) via electrostatic interaction.
• Characterization of membrane structure, surface properties, and wetting resistance.

Main Results:

• The PDDA-SiA-FTCS coated membrane exhibited enhanced structure and properties.
• New fluorinated bonds (trifluoromethyl, tetrafluoroethylene) lowered surface free energy.
• The LBL membrane achieved omniphobicity, showing good wetting resistance.
• Stable AGMD flux of 11.22 L/m² h with high salt rejection was achieved using challenging feed water.
• Performance significantly surpassed that of the neat membrane.

Conclusions:

• LBL assembly effectively created omniphobic composite membranes.
• Enhanced membrane properties ensure suitability for long-term AGMD operations.
• These membranes are promising for treating saline wastewater containing low surface tension organic contaminants.