Forward osmosis membranes fabrication and characterization

López Mascarreras, Elena
Forward osmosis (FO) has emerged as a promising membrane technology for water treatments and other industry applications due to their characteristic, it’s low energy requirements and ability to operate without high temperature or pressure values. Unlike the more commonly used membrane technology, reverse osmosis, which relies on hydraulic pressure, forward osmosis uses the osmotic pressure as its main driving force, making it a more energy-efficient option. This study focuses on the fabrication and rear characterization of polymeric forward osmosis membranes with the aim of improving their efficiency and selectivity. Achieving the fabrication of a membrane with great salt rejection and avoiding as much possible fouling and concentration polarization effects, typical of this type of membranes. The organic membranes were fabricated using various polymers through phase inversion and interfacial polymerization methods with a polysulfone (Psf) support layer and a polyamide selective layer respectively. Resulting in two-layers asymmetric membranes, with a thin selective layer over a thicker support layer. The thickness of the support Psf layer was varied to investigate its effect on membrane properties. These were then characterized by measuring their water flux and permeability, salt rejection and morphology, using various techniques, including scanning electron microscopy (SEM), water flux and conductivity measurements. The results of the study revealed a well-structured support layer, with a uniform and finger-like porous morphology and good mechanical resistance. However, there were encountered issues with polyamide layer adhesion, water flux and permeability, which are critical factors in membrane purpose. The experimental results indicate that the polyamide layer is not homogeneous, as evidenced by the high permeability to water and passage of salts. Moreover, during the flux test, a significantly low flux was observed in FO, indicating the possibility of polarization concentration effect in the support layer. In summary, the study achieved good fabrication results for the support layer, indicating a favourable structure, but further improvement is needed for the polyamide selective layer to optimize the membrane's fabrication methods and make it a more viable option for FO applications ​
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