Combined brine concentration and crystallization using air gap diffusion distillation for high-salinity desalination

Conventional desalination technologies have low water recoveries, consume high-grade energy, and require substantial pretreatment and maintenance. To address this, we introduce a combined brine concentrator and crystallizer based on Air Gap Diffusion Distillation (AGDD) that operates without membranes or tube bundles that are prone to scaling or corrosion. A counterflow heat exchanger design is used for latent heat recovery (which minimizes external energy needed), and film-wise evaporation occurs on patterned polymeric heat transfer surfaces (which kinetically hinders salt precipitation and minimizes interfacial adhesion). These design characteristics are leveraged in a bench-scale prototype to demonstrate brine concentration from 7 to 20 wt% (minimal liquid discharge with 70% water recovery), which produces permeate of potable water quality. Further concentration to saturation conditions at 26 wt% demonstrates zero liquid discharge (ZLD), with effective removal of precipitated salts from the evaporator surface. This highlights AGDD's ability to transform brine into freshwater and a source for minerals recovery.