Polycaprolactone-blended cellulose acetate thin-film composite membrane for dairy waste treatment using forward osmosis.

In recent years new sustainable technology for wastewater treatment has emerged, and among them, forward osmosis (FO) has gained importance. FO utilizes osmotic pressure difference across the semipermeable membrane as the driving force to concentrate the wastewater. Further, the surface and physical properties of the semipermeable FO membrane play a crucial role during the FO process in reducing the internal concentration polarization. In general, FO membranes are prepared using cellulose acetate (CA) polymer due to their high hydrophilic nature. However, CA membranes are mechanically unstable for the FO process. Hence, to increase the mechanical strength and flexibility of CA, other polymers are blended along with it. In this present study, we have prepared a phase-inversion membrane using CA blended with polycaprolactone (PCL) polymers. Further, to increase the hydrophilicity of the membrane, a thin-film composite (TFC) layer of polyamide is coated using interfacial polymerization. To increase the antifouling properties of the membrane, graphene oxide (GO) and copper oxide (CuO) nanoparticles (NPs) are incorporated inside the TFC matrix. The prepared NPs and membrane were characterized using Fourier-transform infrared spectroscopy (FTIR), wide-angle X-ray scattering (WAXD), and contact angle. Further, the GO-CuO incorporated TFC coating has improved the hydrophilicity and antifouling properties of the membrane. It was observed that the water flux has increased up to 5 LMH, and reverse solute flux has reduced to 4 GMH. Further, the membrane was utilized to concentrate in situ prepared dairy waste. It was observed that after 60 min of the FO process, the concentration of dairy waste had increased to 23%, with a concentration factor of 0.903. Thus, a prepared TFC phase inversion membrane is potential for dairy wastewater treatment.

Unimpeded permeation of water through biocidal graphene oxide sheets anchored on to 3D porous polyolefinic membranes.

3D porous membranes were developed by etching one of the phases (here PEO, polyethylene oxide) from melt-mixed PE/PEO binary blends. Herein, we have systematically discussed the development of these membranes using X-ray micro-computed tomography. The 3D tomograms of the extruded strands and hot-pressed samples revealed a clear picture as to how the morphology develops and coarsens over a function of time during post-processing operations like compression molding. The coarsening of PE/PEO blends was traced using X-ray micro-computed tomography and scanning electron microscopy (SEM) of annealed blends at different times. It is now understood from X-ray micro-computed tomography that by the addition of a compatibilizer (here lightly maleated PE), a stable morphology can be visualized in 3D. In order to anchor biocidal graphene oxide sheets onto these 3D porous membranes, the PE membranes were chemically modified with acid/ethylene diamine treatment to anchor the GO sheets which were further confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and surface Raman mapping. The transport properties through the membrane clearly reveal unimpeded permeation of water which suggests that anchoring GO on to the membranes does not clog the pores. Antibacterial studies through the direct contact of bacteria with GO anchored PE membranes resulted in 99% of bacterial inactivation. The possible bacterial inactivation through physical disruption of the bacterial cell wall and/or reactive oxygen species (ROS) is discussed herein. Thus this study opens new avenues in designing polyolefin based antibacterial 3D porous membranes for water purification.

Engineering Nanostructures by Decorating Magnetic Nanoparticles onto Graphene Oxide Sheets to Shield Electromagnetic Radiations.

In this study, a minimum reflection loss of -70 dB was achieved for a 6 mm thick shield (at 17.1 GHz frequency) employing a unique approach. This was accomplished by engineering nanostructures through decoration of magnetic nanoparticles (nickel, Ni) onto graphene oxide (GO) sheets. Enhanced electromagnetic (EM) shielding was derived by selectively localizing the nanoscopic particles in a specific phase of polyethylene (PE)/poly(ethylene oxide) (PEO) blends. By introduction of a conducting inclusion (like multiwall carbon nanotubes, MWNTs) together with the engineered nanostructures (nickel-decorated GO, GO-Ni), the shielding efficiency can be enhanced significantly in contrast to physically mixing the particles in the blends. For instance, the composites showed a shielding efficiency >25 dB for a combination of MWNTs (3 wt %) and Ni nanoparticles (52 wt %) in PE/PEO blends. However, similar shielding effectiveness could be achieved for a combination of MWNTs (3 wt %) and 10 vol % of GO-Ni where in the effective concentration of Ni was only 19 wt %. The GO-Ni sheets facilitated in an efficient charge transfer as manifested from high electrical conductivity in the blends besides enhancing the permeability in the blends. It is envisioned that GO is simultaneously reduced in the process of synthesizing GO-Ni, and this facilitated in efficient charge transfer between the neighboring CNTs. More interestingly, the blends with MWNTs/GO-Ni attenuated the incoming EM radiation mostly by absorption. This study opens new avenues in designing polyolefin-based lightweight shielding materials by engineering nanostructures for numerous applications.