Membrane potential across reverse osmosis membranes under pressure gradient

Area of Science:

• Membrane Science and Technology
• Physical Chemistry
• Chemical Engineering

Background:

• Membrane potential is a key parameter for characterizing ion-exchange membranes.
• Limited research exists on membrane potentials in pressure-driven membrane processes like reverse osmosis (RO).
• RO membranes exhibit solvent permeability, complicating traditional membrane potential analysis.

Purpose of the Study:

• To investigate membrane potentials across RO membranes under a pressure gradient.
• To evaluate the applicability of theoretical models for analyzing membrane potentials in RO systems.
• To determine the utility of membrane potential for characterizing RO membrane properties.

Main Methods:

• Experimental measurement of membrane potentials across RO membranes using NaCl and MgCl2 solutions.
• Application of a theoretical model incorporating Donnan equilibrium and the extended Nernst-Planck equation.
• Inclusion of pressure effects in the theoretical analysis.

Main Results:

• Experimental membrane potential data were collected under varying pressure gradients (0-0.3 MPa).
• The theoretical model demonstrated strong agreement with the experimental results.
• Effective charge density of the RO membrane's active layer was successfully characterized.

Conclusions:

• Membrane potential measurement is a viable technique for RO membrane characterization under pressure.
• The developed theoretical model accurately predicts membrane potentials in RO systems.
• This method provides valuable insights into the effective charge density of RO membrane active layers.