TITLE: Biomimetic Membrane Coatings for >2x Higher Flux Wastewater Treatment Using Forward Osmosis, Microfiltration and Ultrafiltration
WRITTEN BY: Abed-Amoli A, McKenzie E, Kamiya T, Richardson TJ, Flynn MT, Berliner A, and Brozell AM
PRESENTED AT: AMTA Membrane Technology Conference & Expo
10-14 March 2014, Las Vegas, Nevada
ABSTRACT: Active layers enhance or enable the function of membranes. For example, thin film polyamide active layers enable ultrafiltration membranes to function as reverse osmosis membranes do to the poor solubility of salt in the polyamide active layer. In biology, the cell uses molecular bilayers comprised of lipids to separate solutes inside and outside of the cell. Lipid only mimics of the cellular membrane have demonstrated three orders of magnitude higher permeability and six orders of magnitude higher salt rejection than current forward osmosis membranes.
Here we present the properties of active layers for ultrafiltration and microfiltration membranes containing lipid inspired active layers. In addition, these membranes can be used in forward osmosis applications. These active layers are comprised of a z-dimensional structure of alternating lamella of silica and surfactants. The natively hydrophilic silica and polar surfactant surface demonstrate >50% increase in wetting in comparison to poly sulfone and poly ethersulfone membranes. The charge of the surfactants can be non-ionic, cationic, anionic, or zwitterionic. Additionally, the in plane surface charge density of the surfactant lamella is calculated to be as high as +1e or -1e per 45 amu versus -1e per 426 amu for amorphous polysulfone. Surfactant based membranes can be cationic, anionic, zwitterionic or non-ionic, a desirable feature for the development of process specific membranes. When the active layer is applied to an ultrafiltration membrane, the layer is pore spanning as observed as a measurable decrease in molecular weight cutoff. When the active layer is applied to a microfiltration membrane, the layer is conformal as observed as no change in the molecular weight cutoff.
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