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Inorganic-polymer hybrid, thinfilm nanocomposite nanofiltration (TFN-NF) membranes prepared by in situ interfacial polymerization of branched polyethyleneimine and trimesoyl chloride, with simultaneous impregnation of as-synthesized hexagonal wurtzite ZnO nanocrystals (nano-ZnO), either through aqueous or organic phase, have been extensively characterized. XPS analysis revealed that there was no inter-atomic charge transfer between nano-ZnO and host polyamide matrix, indicating that no formation of chemical bonding occurred between them in the skin layers of the membranes. The type of interaction present within the nanocomposite polyamide matrices of the membranes was through formation of noncovalent type secondary chemical interactions with peripheral hydroxyl groups of nano-ZnO and polyamide network as substantiated through FTIR analysis. SEM revealed the formation of distinct patterns and coils, through multiple-point interactions between the nano-ZnO and the polyamide network in the membranes' skin surfaces when introduced through aqueous amine phase.However, when introduced through the organic phase, nanomaterials remained distributed as discrete clusters within the membranes' skin layers because of lack of polar environment around the reaction zone, further emphasizing the role of the medium in which the nanomaterials are incorporated. AFM showed variation of surface roughness features with change in the precursor medium of introduced nano-ZnO. Nanofiltration performance towards different solutes, providing differential rejections in the order of MgCl 2 > NaCl $ Na 2 SO 4 , revealed that the membranes were distinctly positively charged.Solvent fluxes of the membranes were significantly higher when nanomaterials were introduced through the aqueous phase as compared to the organic phase.

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A novel polysulfone–cerium oxide (Psf–ceria) mixed-matrix membrane (MMM) with enhanced γ radiation resistant property was developed. Ceria nanoparticles were synthesized by gel-combustion route and then various concentrations of ceria (0.1–2% of Psf) were incorporated in the polysulfone matrix to synthesize Psf–ceria MMMs. Radiation stability of the synthesized membranes was checked with γ radiation doses of 100, 500, and 1000 kGy. Ceria nanoparticles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, small-angle X-ray scattering (SAXS), transmission electron microscopy, and energy dispersive X-ray spectroscopy techniques. These characterizations confirmed the successful synthesis of pure, crystalline, and 12 nm average size ceria nanoparticles. Psf–ceria MMMs were synthesized by non-solvent-induced phase inversion technique. The effect of radiation on the morphology and topography of membranes was analyzed using scanning electron and atomic force microscopy studies. The physicochemical properties were examined by drop shape analyzer, Fourier transform infrared spectroscopy, gel permeation chromatography, and XRD studies. These analyses confirmed that ceria nanoparticles were uniformly distributed throughout the Psf membrane matrix without any chemical interaction between the ceria and Psf. The internal structure was evaluated by positron annihilation lifetime spectroscopy and SAXS techniques. The mechanical properties were assessed by universal testing machine. The performance of the membranes was analyzed through pure water permeability and solute (poly­(ethylene oxide), 100 kDa) rejection studies. Psf–ceria MMMs showed enhanced stability in the performance compared to that of control Psf membrane. The stability of ceria is due to its two oxidation states and its ability to scavenge free radicals by swiping between those two states (Ce4+ ↔ Ce3+). This makes the MMMs radiation resistant, with 0.5–1% loaded Psf–ceria membrane five times enhanced life span in intermediate liquid radioactive effluent environment, compared to control Psf membrane.

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Thin film composite (TFC) type positively-charged nanofiltration membranes, bearing fixed quaternary ammonium moieties, have been developed and studied. Branched polyethyleneimine (PEI) was functionalized by reaction with glycidyl trimethyl ammonium chloride (GTACl) to introduce quaternary ammonium chloride. Positively-charged TFC membranes were prepared by in situ interfacial polymerization of functionalized PEI and terephthaloyl chloride. The effects of variation of chemical compositions and other experimental conditions such as curing temperature and duration of curing on the performances of the membrane were studied. ATR FT-IR spectroscopy was done to establish the presence of charge-bearing groups in the membrane. The membranes were tested using single solute feed solutions of NaCl, Na 2 SO 4 , CaCl 2 , and MgSO 4 . Positive charges on the membranes were estimated in terms of their ionexchange capacities (IEC). The values were also correlated to the solute-rejection properties of the membranes.

The salient features of a nanostructured carbonaceous material like graphene or graphene oxide have provided innovative alternatives for the development of nanocomposite membranes with better selectivity without having a compromise in throughput, which as a result have a promising role to play in desalination and water purification. Here, nanostructured reduced graphene oxide (nRGO) is synthesized from graphite powder and characterized. Using non-solvent induced phase inversion technique, a series of nanocomposite ultrafiltration (UF) membranes are developed by in situ impregnation of the as synthesized nRGO in polysulfone (Ps) polymer matrix with variation of nRGO from 1 to 8 w/w%. The physicochemical features and transport properties offered by the membranes are evaluated. Structural characterization of the Ps-nRGO composite UF membranes is done by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The variation in porous morphology of the membranes upon impregnation of nRGO is evaluated by scanning electron microscopy. Variation in skin surface topography is analyzed by atomic force microscopy. The change in surface hydrophilicity is evaluated by contact angle studies. The thermal and mechanical properties of the membranes are assessed by thermogravimetric analysis and tensile strength measurements, respectively. The studies reveal that an optimum loading of nRGO (2 w/w%) in the Ps matrix resulted in membranes with elimination of the trade-off between the flux and selectivity that exists with the conventional UF membranes. In addition, the optimum loading of nRGO resulted in membranes with improved thermal and mechanical stability. Thus, nRGO as an emerging potential nanofiller can lead to the development of an ideal membrane with desirable attributes.