Membrane distillation - operating principles and achievements for industrial translation

Membrane distillation (MD) is a separation technique that can be used to treat a variety of liquids, including brackish water, seawater, radioactive wastewater, mining water, wastewater and reverse osmosis (RO) concentrates. The DM process is hybrid, combining the use of conventional thermal distillation and porous hydrophobic membranes, and corresponds to the transport of thermally driven steam across membranes whose driving force is the difference in steam pressure between the two sides of the membrane. Various processes can be employed to facilitate vapor condensation on the permeate side of the membrane, such as the use of an air gap, sweeping gas or vacuum. Non-volatile species, on the other hand, are retained on the upstream side, where the membrane feed stream is located. As a result, DM enables molecules to be separated according to their difference in volatility.

DM has advantages over other separation techniques, such as a lower feed temperature between 50°C and 90°C, lower hydraulic pressure than the reverse osmosis process, lower clogging, treatment of high-salinity water, high-purity water production and a good compromise between specific enthalpy and efficiency . However, due to the lack of a suitable and adaptable membrane, clogging, pore wetting, water efficiency and low permeate flow are the main problems for membrane distillation. Due to its unique properties, DM can be used alone or in combination with other separation techniques, as a final step in the environmental, food, pharmaceutical and nanotechnology industries. It is mainly used in the desalination of seawater, brackish water, the treatment of industrial wastewater, the preparation of distilled, pure or ultrapure water, as well as in the production of liquid food concentrates, and for the removal of volatile molecules from fruit juices, alcohols, halogenated VOCs and benzene.

In this article, we will define the underlying concepts of membrane...