Solar-Driven Thin Air Gap Membrane Distillation with a Slippery Condensing Surface

Abstract

Membrane-based desalination is essential for mitigating global water scarcity; yet, the process is energy-intensive and heavily reliant on fossil fuels, resulting in substantial carbon emissions. To address the challenges of treating seawater, produced water, brackish groundwater, and wastewater, we have developed a thin air gap membrane distillation (AGMD) system featuring a novel slippery condensing surface. The quasi-liquid slippery surface facilitates efficient condensate water droplet removal, allowing for the implementation of a 1 mm thin air gap. This advancement has led to a 2-fold increase in permeate flux without lowering the thermal efficiency while preventing permeate flooding. Furthermore, the thin AGMD system, employing a cost-effective zirconium nitride/poly(vinylidene fluoride) (ZrN-PVDF) composite membrane, has been demonstrated for solar-driven desalination. Experimental results indicate that reducing the air gap from 2 to 1 mm enhances the permeate flux by 150%.