A Mechanistic Study of Arsenic (Iii) Rejection by Reverse Osmosis and Nanofiltration Membranes

273 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.Reverse osmosis/nanofiltration (RO/NF) membranes are capable to provide an effective barrier for a wide range of contaminants (including disinfection by-products precursors) in a single treatment step. However, solute rejection mechanisms by RO/NF membranes are not well understood. The lack of mechanistic information arises from experimental difficulties faced when evaluating water/solute transport phenomena within the ultrathin membrane active layers (< 150 nm) of RO/NF membranes.The main objective of this study was to apply Rutherford backscattering spectrometry (RBS) to determine the partition coefficients of arsenious acid (H3AsO3) and other solutes, and the concentration of charged chemical groups in the active layers of RO/NF membranes with the goal of elucidating the mechanisms underlying the difference in H3AsO 3 rejection between commercial polyamide RO/NF membranes. Then, the role of water permeability, the H3AsO3 partition coefficient, and the H3AsO3 diffusion coefficient in H3AsO 3 removal efficiency was assessed to find key water/H3AsO 3 transport phenomena controlling H3AsO3 removal efficiency. Experimental observations were then used to provide recommendations for physico-chemical properties of polyamide active layers that would result in high H3AsO3 removal efficiency. Another main objective of this study was to investigate the influence of active layer hydrophilicity on solute removal efficiency. This objective has been achieved by characterizing Rhodamine-WT and H3AsO3 removal efficiency by newly developed RO/NF membranes having rigid star amphiphiles (RSAs) as an active layer material. The knowledge obtained from this study will also be useful to guide the development of more effective RO/NF membranes.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD