Analysis of the permeation and separation of electrolyte solutions through reverse osmosis charged membranes

Various charged homogeneous membranes were fabricated by blending an ionic polymer with a nonionic polymer in different ratios. In this study, sodium alginate, chitosan, and poly(vinyl alcohol) were employed as anionic, cationic, and nonionic polymers, respectively. Swelling ratios of the charged membranes were measured in water and the electrolyte solutions of Na2SO4, MgSO4, NaCl, and CaCl2. The permeation and separation behaviors of the salt aqueous solutions have been investigated through the charged membranes with various charge densities. As the content of the ionic polymer increased in the membrane, the hydrophilicity of the membrane increased and pure water flux as well as solution flux increased correspondingly, indicating that the permeation performance through the membrane is determined mainly by its hydrophilicity. When the membrane was charged strongly, electrostatic interactions between the charged membrane and the ionic solute molecules were observed to be attributed to salt rejection to a g...