Tailoring the performance of thin film nano composite reverse osmosis polyamide membranes for water desalination applications

Abstract

The development of cutting-edge technologies for effective water desalination is required due to the critical global issue of clean water scarcity. Reverse osmosis (RO) membranes made of thin-film nanocomposite (TFN) layers with incorporated nanomaterials have received substantial research as an energy-efficient material because of their flexible characteristics and improved water/salt separation abilities. Metal organic frameworks (MOFs, also known as porous coordination polymers), which are three-dimensional structures consisting of metal-containing nodes connected by organic linkers, have recently come to be recognized as a novel class of porous materials with a wide range of technological facets. In this study, the zeolitic imidazolate frameworks (ZIFs), a subclass of MOFs, were investigated for water desalination applications. ZIFs are an entirely novel, distinctive type of metal organic frameworks consisting of metal ions and imidazole linkers. ZIFs have many advantages, including a large surface area, tunable pore size, controlled topologies, small pore diameter, high thermal or chemical stability, and an abundance of metal as well as organic substances in their scaffolds. These features make ZIFs excellent precursors for the porous carbon and similar nanostructures that can be used as functional materials. In the current work, we have synthesized 3D graphene using the direct carbonization approach, as well as several classes of carbon-reinforced ZIF-based hybrid nanostructures, notably ZIF-8 and its individual composites with 3D graphene. The synthesized materials are characterized using XRD, SEM, IR, TGA, EDX, BET, and RAMAN. By employing XRD analysis, it was discovered that ZIF-8 nanoparticles have average crystallite sizes of 19.74 nm crystallizing in the cubic phase, as predicted by the Debye-Scherrer equation. SEM images of ZIF-8 nanoparticles revealed a rhombic dodecahedral geometry exhibiting an apparent uniform size around 133nm and membrane images displayed the usual ridge and valley shape of aromatic polyamide (PA) as well as BET surface area of 1242.548 m2/g. The prepared sample ZIF-8 displays the major band at 460cm-1, which is the vibration caused by the stretching of Zn-N. ZIF-8 is thermally stable up to 490ºC . The D band (1338 cm-1) and the G band (1574cm-1) are the two peaks of the 3D Graphene's Raman spectra, respectively. The integration of functional nanoparticles is a promising way to improve or generate unique material features, such as the improvement of permeability or selectivity linked to water filtration and reuse. TFN RO trilayered membranes were fabricated using top layer of ZIF-8 nanoparticles with different wt% incorporated polyamide membranes, enveloped on polysulfone (as middle layer) overlayered on PET support (bottom layer). The main goal was to examine the precise impacts of porous ZIF-8 nano structures on the separation abilities of TFN membranes. Following this, the ZIF-8 modified TFN membranes' apparent morphology, roughness, or hydrophilicity were altered, which had an impact on the TFN membranes' salt and water rejection capability. Our findings highlighted the significance of MOFs size in further research of TFN membranes including MOFs by showing that the TFN membrane containing ZIF-8 with 0.008wt% showed the best performance owing to the largest dispersion in polyamide layer. The effective incorporation of ZIF-8 nanoparticles in TFN membranes raised the water permeation of TFN-ZIF-8(0.008wt%) to 2.84 Lm-2h 1bar-1, with the maximum NaCl rejection to 95.56% compared with pristine TFC and other wt% of ZIF-8/PA TFN membranes. The as synthesized membranes show the better potential for its use in water desalination applications.