Membrane distillation (MD) is a thermal driven desalination technology using hydrophobic membranes for separation. In MD, heat is utilized to compensate the latent heat of evaporation, and ultrapure water desired by the industry is produced in the process. It can treat streams containing high total dissolved solids with nearly complete rejection to non-volatile matters. However, the targeted fluids are mostly highly saline and contain complicated organic and inorganic chemicals, which incur fouling and scaling to the hydrophobic membranes. Thus, understanding the fouling/scaling phenomenon of hydrophobic membranes has long been the research focal of MD.
Recently, researchers have been attempting to adopt superhydrophobic membranes for improving the scaling and fouling resistance of MD. But discrepancy in results when using different models has been reported.
To unravel this puzzle, a research team led by Prof. HE Tao at the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences, collaborating with Prof. YIN Huabing at University of Glasgow in the UK and Prof. VOLKOV Alexey from A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, proposed a hydrodynamic theory of slippery surface for fouling/scaling resistance of superhydrophobic membranes.
To prove the theory, the scientists created and implemented a delicate design of a porous membrane with micro-pillar arrays. A superhydrophobic membrane was successfully prepared using a micromolding phase separation (mPS) method.
The team further utilized a rheolometry measurement to quantify the slip length of the membrane surface. Simulation of the surface wetting indicated that there is a strong correlation of surface wetting, slip and scaling/fouling resistance.
The new framework for analyzing the fouling/scaling behavior of MD can identify the wetting and hydrodynamic character of the membrane, which is important for hydrophobic membrane design and further development of membrane distillation.
The latest result on the hydrodynamic behavior and scaling/fouling resistance of MD membranes was published in Desalination entitled "Understanding the fouling/scaling resistance of superhydrophobic/omniphobic membranes in membrane distillation."
Fig.1 Scaling mitigation in membrane distillation (Image by Prof. HE's group)
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