Transport of Solutes and Macromolecules through Reverse Osmosis and Nanofiltration Membranes

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

0332217 Marinas The primary objective of this research is to elucidate the mechanisms by which water contaminants, ranging from small neutral molecules to large macromolecules, permeate through reverse osmosis and nanofiltration membranes. Selected solutes and macromolecules are arsenious acid, atrazine (216 Daltons), Rhodamine WT (480 Daltons), and three coliphages (fr, MS2, T4) ranging in size from 19 to 80 nm. This list resulted from a compromise among several criteria including the selection of water contaminants of current interest and surrogates used to assess the performance of RO/NF membranes, small solutes and macromolecules known to be poorly-rejected by some by RO/NF membranes, and compounds quantifiable in multi-solute samples with relatively simple interference-free analytical techniques. The scope of work of the project is designed to develop a fundamental understanding for the mechanisms responsible for the permeation of water and various types of solutes through RO and NF membranes including elucidating the role of the concentration polarization phenomenon in the overall transport of target solutes and macromolecules. In order to accomplish this goal, permeation experiments will be performed to characterize the contribution to overall solute/macromolecule permeation by sorption/diffusion/desorption through the membrane polymer matrix and advection through membrane nanopores, as well as the effect of concentration polarization on both types of permeation. Experimental variables under consideration include hydraulic pressure, background and target solute concentration, temperature, and pH. Then, the size distribution of nanopores in the active layers of RO and NF membranes will be characterized by a combination of atomic force and scanning electron microscopy, and gas adsorption/desorption techniques. It is anticipated that characterizing the pore size distribution of RO/NF membranes will require integrating the results obtained with these three methods. The final task of the study will be the development of a mechanistic model to represent the permeation of water, solutes and macromolecules through RO and NF membranes.