Free-standing, thin-film, symmetric membranes: Next-generation membranes for engineered osmosis

The support layer of an asymmetric thin-film composite membrane results in structural resistance (internal concentration polarization) that significantly undermines engineered osmosis. Increasing the porosity and reducing the thickness and tortuosity of the membrane support layer reduces structural resistance; however, internal concentration polarization still impacts membrane performance. A novel, ultrathin, free-standing and symmetric membrane has been synthesized using sulfonated polyether ketone and tested for forward osmosis applications. This membrane is composed of a protonic acid group containing an aromatic polyether resin with sulfonated structural units. Polyether ketone provides high mechanical strength essential for ultrathin freestanding membranes, while sulfonation enhances the membrane hydrophilicity. These sulfonated polyether ketone membranes show promising water flux performances with impressive mechanical strength under the hydraulic operating conditions used for a FO process.