Marangoni stress induced by free-surface for pressure reduction in reverse osmosis

• Published in: Desalination Vol. 433; pp. 151 - 154
• Main Author: Arias, Francisco J.
• Format: Journal Article Publication
• Language: English
• Published: Elsevier B.V 01-05-2018
• Subjects: Aigua salada; Concentration gradient; Dessalatge; Enginyeria mecànica; Marangoni stress; Mecànica de fluids; Osmosi inversa; Reverse osmosis; Reverse osmosis process; Saline water conversion; Àrees temàtiques de la UPC; Reverse osmosis; Marangoni stress; Concentration gradient
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2018.01.006

Marangoni hydrodynamic motion and its potential technological application in reverse osmosis (RO) process for seawater desalination is discussed. The fundamental core idea in this note is the possibility to take advantage of the inherent concentration gradient in a RO process. It is well known that to run a RO process, it is necessary to apply a hydrodynamic pressure to overcome the osmotic pressure, however, by inducing a free-surface, e.g., a Leidenfrost surface, on the membrane wall, an additional hydrodynamic Marangoni stress could be generated, which, likewise than the osmotic pressure is driven by the concentration gradient but acting in the opposite direction, i.e., reducing the external hydraulic pressure to be applied. Utilizing a simplified geometrical and physical model, an analytical expression for the pressure reduction was derived. One important preliminary result in this work, is that the Marangoni stress can provide pressure against the osmotic pressure for membrane porous that are less than micrometric size.
•Possibility to promote Marangoni stress by harnessing concentration gradients in pressure-driven filtration process•Induced Marangoni stress acting in opposite direction than osmotic pressure•Induced Marangoni stress reducing external required pressure in ultrafiltration operations