Synthesis, characterization and application of novel high flux FO membrane by layer-by-layer self-assembled polyelectrolyte

For the development of forward osmosis (FO) technology, proficient membranes are required for separation with appropriate transport characteristics. Polymer nanocomposites have been showing a great flexibility for tailoring membrane substrate. A layer-by-layer (LbL) method of polyelectrolyte has unveiled the best option for fabricating the required separation layer. In this research work, the nanocomposite of polyvinyl alcohol (PVA) and montmorillonite clay (surface modified with 25–30 wt% methyl dihydroxyethyl hydrogenated tallow ammonium (TA) (MMt-TA)) was used for membrane substrate fabrication. Particle size was measured for ensuring the clay size in nanorange. The pore forming agent was also added to enhance the porosity of FO substrate. Chitosan (CH) (polycation) and polyacrylic acid (PAAc) (polyanion) were employed as polyelectrolyte for surface modification of prepared substrate with three layers of CH/PAAc by the LbL method. The prepared nanocomposite membrane was named as “(PVA/MMt-TA/LiCl) 3LbL”. (PVA/MMt-TA/LiCl) as a substrate and (PVA/MMt-TA/LiCl) 3LbL as FO membrane were characterized by scanning electron microscopy (SEM) for morphology. Thermogravimetric (TGA) analysis was used to understand the thermal behaviour of substrate as well as FO membrane. Substrate membrane porosity was also checked. (PVA/MMt-TA/LiCl) 3LbL membrane was tested on two feed solution i.e. deionised water (DI) and synthetic wastewater. Due to the formation of the high hydrophilic substrate, membrane showed high water flux (37.65 l m−2 h−1 (LMH)) and polyelectrolyte active layer restrained draw solute diffusion from draw solution to feed solution. It showed remarkable separation (0.2813 g−2 h−1(gMH)) in active layer facing draw solution (AL-DS) mode for DI water as feed and 2 M NaCl solution as draw solution. Similarly, for synthetic wastewater, the flux was 34.35 LMH. This LbL approach has revealed that it is possible to fabricate novel high flux FO membranes with high water permeability and low reverse salt diffusion.