Effects of water chemistry on structure and performance of polyamide composite membranes
Journal of Membrane Science
Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, United States; California NanoSystems Institute, University of California, Los Angeles, CA, United States; Institute of the Environment and Sustainability, University of California, Los Angeles, CA, United States; Department of Applied Chemistry, University of Johannesburg, South Africa
The effects of feed solution ionic strength, pH and divalent cation content on NF/RO membrane structure and performance were elucidated experimentally and fitted with a modified solution-diffusion transport model that describes polyamide thin film free volume through an effective pore radius and structure factor. All the membranes tested became more hydrophilic and swollen with increasing feed solution ionic strength, pH, and divalent cation concentrations. Generally, water permeabilities of all three membranes decreased with ionic strength and divalent cation content, but increased with pH. For RO membranes, neutral solute rejection decreased with pH and divalent cation content, but increased with ionic strength and the salt rejection remained independent with water chemistry except for very low pH of 3; for a NF membrane, solute rejection was more sensitive to water chemistry and neutral solute rejection decreased with ionic strength and pH, but increased with divalent cation content. The results presented herein provide new insight into the fundamental relationship between changes in NF/RO membrane structure and performance. Ultimately, these new insights may be useful in selection of already commercial or design of new NF/RO membranes for removal of chemicals of emerging concern in water treatment. © 2013 Elsevier B.V.
Effective pore radius; Polyamide composite membranes; Polyamide thin films; Solution-diffusion; Structure and performance; Transport modeling; Water chemistry; Water permeability; Chemical water treatment; Composite membranes; Ionic strength; Membrane structures; Nanofiltration; Polyamides; Positive ions; Reverse osmosis; Hydrochemistry; divalent cation; polyamide; sodium chloride; water; article; chemistry; diffusion; hydrophilicity; ionic strength; membrane; membrane structure; nanofiltration; pH; priority journal; reverse osmosis; water permeability; water treatment