Natural Vacuum–Enhanced Air‐Gap Membrane Distillation (NV‐AGMD): A Proof‐Of‐Concept Experimental and Theoretical Study

ABSTRACT Desalination of saline water via air gap membrane distillation (AGMD) can be enhanced by reducing the air‐gap pressure. In this study, we present a proof‐of‐concept for a novel “natural vacuum–enhanced air gap membrane distillation” (NV‐AGMD) system in which the reduction of air‐gap pressure has been achieved using a water column. Our results demonstrate that this approach increases the permeate flux without additional energy demand. For 24‐h tests with 0.5 M feed salinity, a flow rate of 60 L/h and temperatures of 85°C, the proposed method increased the average flux by 290% compared with conventional AGMD. With re‐vacuuming every 4 h using the natural vacuum approach, the flux improvement reached about 454%. Moreover, the electrical energy consumption per cubic meter of produced water decreased by roughly 49% without re‐vacuuming and 58% with re‐vacuuming relative to standard AGMD.