The Influence of water permeability, solute resistance and mass transfer coefficient on water flux behavior in forward osmosis
Abdulrahman Alalawi,Ibrahim S. Al-mutaz,Nawaf Bin Darwish,Ibrahim A. Alsayer
Abstract
Forward osmosis (FO) is an innovative membrane process with growing potential. Mathematical models for predicting water flux in forward osmosis (FO) are valuable for understanding the system behavior and helpful in optimizing the performance. This work explores the relationship between water flux key governing parameters, namely water permeability, solute resistance and mass transfer coefficient which affect the water flux behavior. The influence of these parameters on water flux behavior is analyzed, highlighting how water permeability governs the water transport capacity, solute resistance dictates the rejection of solutes, and the mass transfer coefficient reflects the impact of external boundary layers. For both orientations the membrane active layer faces the feed solution (AL-FS) and the membrane active layer faces the draw solution (AL-DS), water flux increases with an increase in water permeability since water flux is directly proportional to the membrane water permeability as given by the basic flux equations. The mass transfer coefficient, whether on the feed side (AL-FS mode) or on the draw side (AL-DS mode), does not significantly influence the enhancement of water flux associated with increased membrane water permeability. On the other hand, solute resistance has a pronounced effect on the water flux with an increase in water permeability. At higher values of solute resistance, the increase in water flux resulting from enhanced water permeability becomes progressively limited, due to the intensified internal concentration polarization that diminishes the effective osmotic driving force.
Key Words
forward osmosis; mass transfer coefficient; solute resistance; water flux; water permeability
Address
Abdulrahman Alalawi, Nawaf Bin Darwish — Desalination Technologies Institute, King Abdulaziz City for Science and Technology, Saudi Arabia
Ibrahim S. Al-mutaz — Chemical Engineering Dept., College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
Ibrahim A. Alsayer — Department of Chemical Engineering, Northern Border University, Arar, Saudi Arabia
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