Advances in Solvent‐Resistant Nanofiltration Membranes

Abstract

Nanofiltration (NF) and reverse osmosis (RO) are well-established membrane technologies for applications involving aqueous streams. The principles of NF transport (diffusion, convection, and Donnan exclusion) are effectively used to develop novel membrane materials and applications in aqueous medium. Use of NF in a non-aqueous medium holds strong potential for the food, refining, and pharmaceutical industries because of the low energy costs involved with such membrane processes. Further understanding and development of solvent-resistant NF membranes provides opportunities for various hybrid processing ranging from reactor-membrane to distillation-membrane combinations. This paper provides a comprehensive overview of literature results and our own work in the area of non-aqueous systems. For solvent-based systems, potential membrane swelling and solvent-solute coupling needs to be considered for membrane design and transport theories. A simplified transport theory for pure solvents has been developed using solvent (molar volume, viscosity) and membrane properties (membrane surface energy). This model and has been verified with literature data for both hydrophilic and hydrophobic membranes. Membrane characterization and preconditioning aspects need to be given serious consideration for evaluating membrane performance. In addition to permeability and separation results, some novel applications of NF in non-aqueous solvents are included in this paper.

Fundamental studies on the performance of a hydrophobic solvent stable membrane in non-aqueous solutions

“…Although presently available membranes still have limitations with respect to solvent stability and separation performance, the achieved results show the potential of such a process. The majority of published results in this field are related to polymeric membranes [1][2][3][4][5][6][7][8][9][10][11]. However, it should be noted that significant progress was achieved in the development of inorganic membranes [12].…”

New experimental measurements of solvent induced swelling in nanofiltration membranes

“…For example, the development of polymeric solvent resistant nanofiltration (SRNF) membranes has attracted much attention and enabled several potential applications in the processing of organic solvent streams [1][2][3][4]. Although precise transport mechanisms across the convection-diffusion spectrum are an ongoing topic of debate, it is generally accepted that polymer swelling plays a significant role in determining levels of flux and rejection [2,5,6].…”

Physicochemical Characterization of Transport in Nanosized Membrane Structures

“…Swelling of the membrane by the organic solvents is one of the most observed phenomena in solvent NF. [5,14,15] Manjula et al [16] claimed that a higher degree of swelling of polymeric membranes should be expected when the solubility parameter of solvent and membrane are closer together. Van der Bruggen et al [17] noted the importance of solvent polarity in SRNF transport.…”