Synthesis and characterization of silica gel-polyacrylonitrile mixed matrix forward osmosis membranes based on layer-by-layer assembly

Silica gel (SG)-polyacrylonitrile (PAN) composite forward osmosis (FO) membranes have been synthesized and characterized in the present work. The incorporation of SG particles into the PAN support layer significantly changed its water permeability and salt rejection rate. In the range of 0.25-1.0 wt.% SG loading, water permeability of membranes were enhanced after the embedment of SG, most likely due to the both porous nature of SG and the enhanced substrate porosity. However, a reduction in both water permeability and salt rejection was observed if further increase in SG loading (2.0 wt.%), possibly as a result of the agglomeration of SG. The most permeable SG-PAN FO membrane (M1.00, with 1.0 wt.% SG loading) had a significantly higher water permeability compared to the control pure PAN FO membrane (M0.00). This membrane achieved high FO water fluxes of >100 L/m² h was achieved by using the 1 M MgCl ₂ as the draw solution (DS) and 0-10 mM NaCl as the feed solution (FS). To the best knowledge of the authors, this is the first study reporting the development and application of SG-PAN mixed matrix FO membranes (MMMs) based on layer-by-layer assembly.