Enhancing the permselectivity of thin-film composite poly(vinyl alcohol) (PVA) nanofiltration membrane by incorporating poly(sodium-p-styrene-sulfonate) (PSSNa)

Elevated Performance of Thin Film Nanocomposite Membranes Enabled by Modified Hydrophilic MOFs for Nanofiltration

Metal-organic frameworks (MOFs) are studied for the design of advanced nanocomposite membranes, primarily due to their ultrahigh surface area, regular and highly tunable pore structures, and favorable polymer affinity. However, the development of engineered MOF-based membranes for water treatment lags behind. Here, thin-film nanocomposite (TFN) membranes containing poly(sodium 4-styrenesulfonate) (PSS) modified ZIF-8 (mZIF) in a polyamide (PA) layer were constructed via a facile interfacial polymerization (IP) method. The modified hydrophilic mZIF nanoparticles were evenly dispersed into an aqueous solution comprising piperazine (PIP) monomers, followed by polymerizing with trimesoyl chloride (TMC) to form a composite PA film. FT-IR spectroscopy and XPS analyses confirm the presence of mZIF nanoparticles on the top layer of the membranes. SEM and AFM images evince a retiform morphology of the TFN-mZIF membrane surface, which is intimately linked to the hydrophilicity and adsorption capacity of mZIF nanoparticles. Furthermore, the effect of different ZIF-8 loadings on the overall membrane performance was studied. Introducing the hydrophilizing mZIF nanoparticles not only furnishes the PA layer with a better surface hydrophilicity and more negative charge but also more than doubles the original water permeability, while maintaining a high retention of Na₂SO₄. The ultrahigh retentions of reactive dyes (e.g., reactive black 5 and reactive blue 2, >99.0%) for mZIF-functionalized PA membranes ensure their superior nanofiltration performance. This facile, cost-effective strategy will provide a useful guideline to integrate with other modified hydrophilic MOFs to design nanofiltration for water treatment.

Facile synthesis of boehmite/PVA composite membrane with enhanced adsorption performance towards Cr(VI)

A novel boehmite/PVA composite membrane (BPCM) with remarkably enhanced adsorption performance towards Cr(VI) was successfully synthesized from Al(NO3)3·9H2O using HAc as the peptizing agent via a facile sol-gel method. The physicochemical properties of the BPCM, the boehmite powder (BP) without PVA and a commercial boehmite powder (CBP) were comparatively characterized by XRD, TGA-DSC, FT-IR and XPS. Batch adsorption experiments showed that the adsorption performance of the BPCM is much better than those of BP and CBP. Its adsorption process was well described by the pseudo-second-order kinetic model, and its equilibrium data fit the Langmuir isotherm well with a maximum adsorption capacity of 36.41mgg(-1). Its interference adsorption experiment in presence of coexisting anions showed that SO4(2-) and HPO4(2-) have greater effect than those of the Cl(-), F(-), C2O4(2-) and HCO3(-). A three step action mechanism including adsorption of Cr(VI) anions, complexation between Cr(VI) anions and the functional groups on the surface of BPCM, and the reduction of Cr(VI) to Cr(III) was proposed to illustrate the adsorption process. This efficient film could be easily separated after adsorption, exhibiting great potential for the removal of Cr(VI) from aqueous solution, and other fields of environmental remediation.

Novel reverse osmosis membranes composed of modified PVA/Gum Arabic conjugates: Biofouling mitigation and chlorine resistance enhancement

A novel crosslinked Poly (vinyl alcohol) (PVA) reverse osmosis (RO) thin film membrane conjugated with Gum Arabic (GA) with superb performance and features was synthesized for water desalination. RO membrane desalination parameters, such as hydrophilicity, surface roughness, water permeability, salt rejection, Chlorine resistance and biofouling resistance were evaluated using a dead end RO filtration unit. The incorporation of Pluronic F127 and the conjugation of Gum Arabic improved the overall RO performance of the membranes. This study has shown that the membrane PVA-GA-5 that contains 0.9wt% Gum Arabic provided excellent permeation, salt rejection, Chlorine and biofouling resistance and mechanical strength. The most remarkable result to arise from this research is that the overall RO performance enhancement has been achieved while utilizing PVA/Gum Arabic as a separation layer without the use of a substrate, which eliminates negative effects associated with the use of a substrate like internal concentration polarization.

Novel organic–inorganic hybrid composite membranes for nanofiltration of acid and alkaline media

Novel NF membranes have been fabricated by a simple and environmentally friendly process for treating wastewater with extreme pH values.