Embedded three spinel ferrite nanoparticles in PES-based nano filtration membranes with enhanced separation properties

In this study, three types of ferrites nanoparticles including CoFe2O4, NiFe2O4, and ZnFe2O4 were synthesized by microwave-assisted hydrothermal method. The X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) were employed to analyze synthesized nanoparticles and fabricated membranes. The morphology of membrane surface was investigated by surface images. The ability of ferrite nanoparticles was evaluated to the separation of sodium salt and heavy metals such as Cr2+, Pb2+, and Cu2+ from aqueous solutions. The modified membrane showed the enhancement of membrane surface hydrophilicity, porosity, and mean pore size. The results revealed a significant increase in pure water flux: 152.27, 178, and 172.68 L·m−2·h−1 for PES/0.001 wt% of CoFe2O4, PES/0.001 wt% NiFe2O4, and PES/0.001 wt% ZnFe2O4 NPs, respectively. Moreover, Na2SO4 rejection was reached 78% at 0.1 wt% of CoFe2O4 NPs. The highest Cr (II) rejection obtained 72% for PES/0.001 wt% of NiFe2O4 NPs while it was 46% for the neat PES membrane. The Pb(II) rejection reached above 75% at 0.1 wt% of CoFe2O4 NPs. The Cu(II) rejection was obtained 75% at 0.1 wt% of CoFe2O4 NPs. The ferrite NPs revealed the high potential of heavy metal removal in the filtration membranes.

Recyclable, Antibacterial, Isoporous Through-Hole Membrane Air Filters with Hydrothermally Grown ZnO Nanorods

Reusable, antibacterial, and photocatalytic isoporous through-hole air filtration membranes have been demonstrated based on hydrothermally grown ZnO nanorods (NRs). High-temperature (300~375 °C) stability of thermoset-based isoporous through-hole membranes has enabled concurrent control of porosity and seed formation via high-temperature annealing of the membranes. The following hydrothermal growth has led to densely populated ZnO NRs on both the membrane surface and pore sidewall. Thanks to the nanofibrous shape of the grown ZnO NRs on the pore sidewall, the membrane filters have shown a high (>97%) filtration efficiency for PM2.5 with a rather low-pressure (~80 Pa) drop. The membrane filters could easily be cleaned and reused many times by simple spray cleaning with a water/ethanol mixture solution. Further, the grown ZnO NRs have also endowed excellent bactericidal performance for both Gram-positive S. aureus and Gram-negative S. enteritidis bacteria. Owing to the wide bandgap semiconductor nature of ZnO NRs, organic decomposition by photocatalytic activity under UV illumination has been successfully demonstrated. The reusable, multifunctional membrane filters can find wide applications in air filtration and purification.

Nano-Fibrous Networks from Co-Assembly of Amphiphilic Peptide and Polyelectrolyte

Organize the matter on an increasingly small scale is sought in order to increase the performance of materials. In the case of porous materials, such as filtration membranes, a compromise must be found between the selectivity provided by this nanostructuring and a permeability in particular linked to the existing pore volume. In this work, we propose an innovative waterborne approach consisting in co-assembling peptide amphiphiles (PA) which will provide nanostructuring and polyelectrolytes which will provide them with sufficient mechanical properties to sustain water pressure. C16-V3A3K3G-NH2 PA nanocylinders were synthesized and co-assembled with poly(sodium 4-styrenesulfonate) (PSSNa) into porous nano-fibrous network via electrostatic interactions. The ratio between C16-V3A3K3G-NH2 and PSSNa was studied to optimize the material structure. Since spontaneous gelation between the two precursors does not allow the material to be shaped, various production methods have been studied, in particular via tape casting and spray-coating. Whereas self-supported membranes were mechanically weak, co-assemblies supported onto commercial ultrafiltration membranes could sustain water pressure up to 3 bars while a moderate permeability was measured confirming the existence of a percolated network. The produced membrane material falls into the ultrafiltration range with a pore radius of about 7.6 nm.