Synthesis and Characterization of Novel Forward Osmosis Thin Film Nano-Composite Membrane to Enhance the Reverse Osmosis Desalination Economics

In this study, two main key features are used for the successful forward osmosis desalination process. The first key is the thin-film nanocomposite membrane fabrication. This key is achieved by consolidating different concentrations of zeolite nanoparticles in the polysulfone supporting sheet (ranging from 0%wt. to 0.6% wt.) to enhance the hydrophilicity and porosity of the membrane. A thin polyamide layer is formed on the top surface of the modified polysulfone by interfacial polymerization of Metaphenylenediamine (MPD) and Trimesoyl chloride (TMC) to fabricate thinfilm nanocomposite (TFNC) forward osmosis membranes for forward osmosis (FO) application. The other key feature that makes the FO practical is selecting the ideal draw solute achieved by selecting sodium chloride as inorganic salt. Sodium chloride is characterized by high osmotic pressure, chemically inert, low membrane reverse solute flux, and easily regenerated. The fabricated TFNC membranes were first tested using a cross-flow RO module to evaluate the effect of different loadings of zeolite nanoparticles on the membrane performance. The FO membrane with 0.4 wt% zeolite in polysulfone matrix (TFNC-0.4%) shows the most promising results through increasing the water flux by 126% than the TFC membranes. Then were tested using a cross-flow FO module with 0.02-0.8 M NaCl concentration as feed solution. Results indicate that the water flux of the TFNC-0.4% was increased by (55%-64%) than the TFC Control membrane depending on the membrane orientation and draw solution concentration. It is observed that the solute reverse flux increased with the increase of the concentration of draw solution. Different characterization tests have been carried out on the forward osmosis membranes to verify their successful preparation and modification and specify the various effects of the zeolite nanoparticles added to the membrane substrate. A sponge-like structure is developed by adding zeolite nanoparticles compared to the TFC membrane, enhancing water permeability. Moreover, an increase in mechanical and thermal properties is detected. Furthermore, the power consumption for the forward osmosis process was [0.72-4.66%] only from the total power consumption of the FO-RO process. The current power cost as OPEX for FO TFNC-0.4% membrane desalination process ranges from 0.072 to 0.132 EGP/m3 compared to the commercial SWRO+PX [5.53 EGP/m3] operated in Hurghada, Red sea, Egypt.