Sanna Kotrappanavar Nataraj

Zeolitic imidazolate framework (ZIF-8) based polymer nanocomposite membranes for gas separation

As synthesised ZIF-8 nanoparticles (size ∼ 60 nm and specific surface area ∼ 1300–1600 m2 g−1) were directly incorporated into a model polymer matrix (Matrimid® 5218) by solution mixing. This produces flexible transparent membranes with excellent dispersion of nanoparticles (up to loadings of 30 wt%) with good adhesion within the polymer matrix, as confirmed by scanning electron microscopy, dynamic mechanical thermal analysis and gas sorption studies. Pure gas (H2, CO2, O2, N2 and CH4) permeation tests showed enhanced permeability of the mixed matrix membrane with negligible losses in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that an increase in the free volume of the polymer with ZIF-8 loading together with the free diffusion of gas through the cages of ZIF-8 contributed to an increase in gas permeability of the composite membrane. The gas transport properties of the composite membranes were well predicted by a Maxwell model whilst the processing strategy reported can be extended to fabricate other polymer nanocomposite membranes intended for a wide range of emerging energy applications.

Chitosan-Based Aerogel Membrane for Robust Oil-in-Water Emulsion Separation.

Here, we demonstrate direct recovery of water from stable emulsion waste using aerogel membrane. Chitosan-based gel was transformed into highly porous aerogel membrane using bio-origin genipin as cross-linking agent. Aerogel membranes were characterized for their morphology using SEM, chemical composition by FTIR and solid-UV. Further, aerogel was tested for recovery of high quality water from oil spill sample collected from ship breaking yard. High quality (with >99% purity) water was recovered with a flux rate of >600 L·m(-2)·h(-1)·bar(-1). After repeated use, aerogel membranes were tested for greener disposal possibilities by biodegrading membrane in soil.

Collective osmotic shock in ordered materials

Osmotic shock in a vesicle or cell is the stress build-up and subsequent rupture of the phospholipid membrane that occurs when a relatively high concentration of salt is unable to cross the membrane and instead an inflow of water alleviates the salt concentration gradient. This is a well-known failure mechanism for cells and vesicles (for example, hypotonic shock) and metal alloys (for example, hydrogen embrittlement). We propose the concept of collective osmotic shock, whereby a coordinated explosive fracture resulting from multiplexing the singular effects of osmotic shock at discrete sites within an ordered material results in regular bicontinuous structures. The concept is demonstrated here using self-assembled block copolymer micelles, yet it is applicable to organized heterogeneous materials where a minority component can be selectively degraded and solvated whilst ensconced in a matrix capable of plastic deformation. We discuss the application of these self-supported, perforated multilayer materials in photonics, nanofiltration and optoelectronics.

Bio-based superhydrophilic foam membranes for sustainable oil–water separation

The development of a low-cost, high-performance, biobased membrane technology has been attempted to treat environmentally sensitive wastewater streams. Novel foam membranes (FMs) were derived from agarose (Agr) and gelatin (Gel) in combination with a non-toxic fruit extract and natural crosslinker, genipin (G). FMs were successfully tested for their oil–water separation efficiencies. FMs attained unique capillary microstructures (10–45 μm) as a result of the controlled lyophilization process, which allows selective permeation of water. Stable microporous membranes with nominal pore sizes in between the microfiltration and ultrafiltration range generated as high as >500 L m−2 h−1 continuous flux with ∼98% pure product water. One of the advantages of these FMs is that after oil–water separation, they can undergo an easy membrane cleaning process, thereby retaining surface activity for long term performance.

Polyaniline Membranes for Separation and Purification of Gases, Liquids, and Electrolyte Solutions

Abstract Conjugated polymers are excellent barriers for membrane separations because their porosity can be controlled at the molecular level through chemical doping. Polyaniline (PANI) is particularly attractive because simple acid/base doping/undoping enables a controllable level of doping that can be readily achieved using dopants of different sizes and shapes. PANI, which belongs to an important member of the family of electrically conducting polymers, has been studied extensively as a membrane due to its distinct electrochemical properties and environmental stability. Adding dopants to PANI leads to a decrease in gas permeability, while removal of these dopants would produce extremely high permeability. This review provides an overview of the use of PANI membrane in gas separation (GS), pervaporation (PV) and electrodialysis (ED) applications. Our discussion will be concerned with the utility of PANI as a homopolymer, blend and composite membrane, discussing a considerable amount of background information on their developments and applications. Various modifications of PANI as efficient membranes and their future prospects in membrane separation and purification technology are discussed. This article was the CEPS Communication # 106. The authors dedicate this review article in honor of Professor Alan G. MacDiarmid, the University of Texas at Dallas, USA (Nobel Laureate in Chemistry, 2000), who visited CEPS in December 2004. His untiring energy to visit and inaugurate the Center of Excellence in Polymer Science at Karnatak University, Dharwad has been a great inspiration to our younger students and scientists.

Deep eutectic solvent promoted one step sustainable conversion of fresh seaweed biomass to functionalized graphene as a potential electrocatalyst

Herein we report a facile method for the scalable production of Fe3O4/Fe doped graphene nanosheets (Fe3O4/Fe–GN) from a naturally abundant seaweed resource. The granules that remained after the recovery of liquid juice from a fresh brown seaweed, Sargassum tenerrimum, were utilized as a raw material and a deep eutectic solvent (DES) generated by the complexation of choline chloride and FeCl3 (ChoCl–FeCl3) was employed as a template as well as a catalyst for the production of graphene nanosheets. Pyrolysis of a mixture of seaweed granules and DES at 700–900 °C under a 95% N2 and 5% H2 atmosphere resulted in the formation of Fe3O4/Fe–GN with a high surface area (220 m2 g−1) and high electrical conductivity (2384.6 mS m−1). The synthesized nanosheets were then tested for their electrocatalytic activity in the oxygen reduction reaction (ORR) in an alkaline fuel cell. The electrocatalyst demonstrated a positive onset potential, high cathodic current density, low hydrogen peroxide formation ( 80% activity of the catalyst, making the functionalized graphene sheets derived from Sargassum tenerrimum a sustainable replacement for existing precious metal-based ORR catalysts.

Electrospun Nanocomposite Fiber Mats of Zinc-Oxide Loaded Polyacrylonitrile

We have demonstrated the feasibility of using electrospinning method to fabricate long and continuous composite nanofiber sheets of polyacrylonitrile (PAN) incorporated with zinc oxide (ZnO). Such PAN/ZnO composite nanofiber sheets represent an important step toward utilizing carbon nanofibers (CNFs) as materials to achieve remarkably enhanced physico-chemical properties. In an attempt to derive these advantages, we have used a variety of techniques such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution X-ray diffraction (HR-XRD) to obtain quantitative data on the materials. The CNFs produced are in the diameter range of 100 to 350 nm after carbonization at . Electrical conductivity of the random CNFs was increased by increasing the concentration of ZnO. A dramatic improvement in porosity and specific surface area of the CNFs was a clear evidence of the novelty of the method used. This study indicated that the optimal ZnO concentration of 3 wt% is enough to produce CNFs having enhanced electrical and physico-chemical properties.

Thin, Flexible Supercapacitors Made from Carbon Nanofiber Electrodes Decorated at Room Temperature with Manganese Oxide Nanosheets

We report the fabrication and electrochemical performance of a flexible thin film supercapacitor with a novel nanostructured composite electrode. The electrode was prepared by in situ coprecipitation of two-dimensional (2D) MnO2 nanosheets at room temperature in the presence of carbon nanofibers (CNFs). The highest specific capacitance of 142 F/g was achieved for CNFs-MnO2 electrodes in sandwiched assembly with PVA-H4SiW12O40nH2O polyelectrolyte separator.

Application of the electrodialytic pilot plant for fluoride removal

Removal of fluorine from water was investigated by electrodialysis (ED) method. In order to check the efficacy of ED unit, parameters like applied potential, the pH; initial fluoride concentrations and flow rates were varied. Significant results were obtained with concentrations of less than 10 ppm. Results were satisfactory in meeting the maximum contaminate level (MCL) of 0.01 ppm for fluoride. Effect of working parameters on energy consumption was investigated using ion-exchange membranes. Results of this study are useful for designing and operating different capacities of ED plants for recovering different ions. The ED plant was found to be satisfactory to produce a good quality drinking water from the simulated mixture by removing the unwanted ions.

Preparation of a natural deep eutectic solvent mediated self polymerized highly flexible transparent gel having super capacitive behaviour

A novel natural deep eutectic solvent (NADES) was prepared by the endothermic complexation of choline chloride (hydrogen bond acceptor) and orcinol (hydrogen bond donor) at room temperature. Among N-isopropyl acrylamide (NIPAM), vinyl acetate (VA) and 2-hydroxyethyl methacrylate (HEMA), only HEMA was found to self-polymerized in the above NADES at room temperature at optimized concentrations, resulting in the formation of a highly stretchable gel (>30 times). Polymerization of HEMA in the DES was established and rheological investigations revealed the highly stretchable behaviour of the gels. The gels obtained with HEMA in the ratio of 0.35, 0.5 and 1% v/v with respect to the NADES demonstrated good capacitive behaviour with metal oxide frame works (>200 F g−1).