Impregnated membranes for water purification using forward osmosis
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Forward osmosis (FO) provides an energy efficient route for seawater desalination and wastewater treatment, because water transport is driven by the osmotic pressure difference across the membrane and there is no need of feed compression. The current FO membranes are comprised of a selective layer on top of a thick microporous support and paper layer, which present significant resistance for water transport, decreasing water flux and preventing FO from wide adoption. This study investigates novel membranes consisting of a porous structure fully impregnated with a hydrophilic polymer. The elimination of the open pore structures in these impregnated membranes minimizes the effect of concentration polarization on water transport, increasing the water flux. More specifically, a series of hydrophilic polymers based on poly(ethylene glycol) diacrylate (PEGDA) were prepared and characterized for water sorption and permeation. Impregnated membranes consisting of crosslinked PEGDA in porous Solupor ® supports were prepared and characterized for the water and salt transport properties using a dead end filtration system, salt kinetic desorption experiments and an FO system. The impregnated membranes show higher performance ratio (defined as the water flux under the FO mode to that from the dead-end filtration system) compared with commercial FO membranes, which indicates the effect of concentration polarization has been reduced in these impregnated membranes.