Membrane distillation of saline feeds and produced water: A comparative study of an air-gap and vacuum-driven modules

Air gap membrane distillation (AGMD) and vacuum membrane distillation (VMD) are two membrane-based desalination processes that utilize temperature differences to generate water vapor for purification. This study evaluated the viability of both processes for treating different types of saline water, such as Arabian Gulf seawater and oil field-produced water. Factors such as feed temperature, feed concentration, recirculation flow rate, air gap, and vacuum space depth were investigated to understand their impact on permeate flux in AGMD and VMD configurations. The results showed that AGMD achieved higher permeate flux at lower feed concentrations, while VMD performed better at higher concentrations. Increasing the feed temperature led to increased permeate flux in both configurations, with AGMD showing a greater increase. Results also indicated that lower gaps were preferred in both configurations, and the tested membranes showcased excellent salt rejection capabilities. These findings provide valuable insights into the potential applications of AGMD and VMD in desalination, especially in regions with water scarcity or pollution.