Technologies, materials, applications, and challenges of membrane distillation: a comprehensive review

Available water resources represent a global challenge due to the increase in population that requires a huge amount of fresh water for different human activities. Water desalination has the potential for freshwater production. The present work focuses on studying the technologies, materials, applications, and challenges inherent in membrane distillation as a membrane-based separation method. The various configurations of membrane distillation are comprehensively illustrated. Advanced materials are examined for membrane distillation. The current paper presents a general overview of desalination classifications to distinguish the properties of membrane distillation. The review reveals that electrically driven desalination technologies, e.g., reverse osmosis (RO), electrodialysis (ED), capacitive deionization (CDI), and mechanical vapor compression (MVC), are more productive than thermally driven desalination technologies, such as solar still (ST), multi-effect distillation (MED), multiple-stage flash (MSF), and MD. Configurations of membrane distillation are various as direct contact membrane distillation (DCMD), air gap membrane distillation (AGMD), sweeping gas membrane distillation (SGMD), and vacuum membrane distillation (VMD). MD systems are more effective in recovering low-grade waste heat and treating high-salinity solutions. Hybrid MD systems achieve high evaporation rates and salt rejection ratios. The membrane distillation systems have different scales, from lab scale to system unit.