Electrically conducting nanofiltration membranes based on networked cellulose and carbon nanostructures

Electrically enhanced fouling control is increasingly applied to membrane-based separation and requires conducting membranes with controlled properties. In this work, electrically conductive membranes based on networked cellulose (NC) and carbon nanostructures (CNS) were fabricated via vacuum filtration, followed by drying at 40 °C. The morphology, structure, mechanical and electrochemical properties of these NC-CNS membranes were characterized and compared with CNS membranes. The effect of incorporating NC on the electrocatalytic activity has been analyzed. It is found that networked cellulose helps to decrease the contact angle of water from 105° to 73°. It is also found that the improved surface hydrophilicity of CNS-NC membrane assists the regeneration of electrode surface during electrolysis process. Networked cellulose yields a more dense structure with the tensile strength exceeding ten times that of CNS alone. The compaction of pore structure via incorporation of NC translates into promising results with respect to nanofiltration of divalent ions, with a rejection efficiency of 60% for MgSO4 and 47% for CaCl2, while maintaining a high flux ≥ 100 L m− 2 h− 1, making them suitable for pretreatment of RO feeds

Facile Synthesis of Copper Oxide Nanoparticles via Electrospinning

A novel approach for synthesizing copper oxide (CuO) nanoparticles (NPs) through electrospinning is reported. The approach is based on producing rough and discontinuous electrospun nanofibers from a precursor based on copper acetate salt and polyvinyl alcohol (PVA) polymer. Selectively removing the polymeric phase from the fibers produced highly rough CuO nanofibers, which were composed of NPs that are weakly held together in a one-dimensional (1D) manner. Sonication in a suitable liquid under controlled conditions completely disintegrated the nanofibers into NPs, resulting in the formation of uniform CuO NPs suspension. Aberration corrected high resolution transmission electron microscope (HRTEM) showed that the obtained NPs are highly crystalline and nearly sphere-like with a diameter of 30 to 70 nm. Thus, electrospinning, which is a low cost and industrially scalable technique, can also be employed for economic and large scale synthesis of NPs

Electrically conductive spacers for self-cleaning membrane surfaces via periodic electrolysis

The use of an electrically conductive membrane has attracted significant interest in water treatment technology due to remarkable performance in fouling mitigation domain. In electrochemical systems, when external potential is applied, water electrolysis occurs and the generated gases efficiently clean the membrane surface. However, fabricating and integrating conductive membranes in current water treatment modules is challenging. The present work applies, for the first time, the electrolysis concept at the spacer component of the module rather than the membrane. Two types of materials were tested, a titanium metal spacer and a polymeric spacer. The polymeric spacer was made conductive via coating with a carbon-based ink comprised of graphene nanoplates (GNPs). A membrane system composed of the carbon coated/titanium metal spacer attached to the surface of a polyvinylidene fluoride (PVDF) microfiltration membrane and was assembled to the case of membrane module. The conductive spacers worked as an electrode (cathode) in electrochemical set-up. The membrane system was subjected to fouling and then exposed to periodic electrolysis, wherein in-situ cleaning of membrane surface by hydrogen bubbles generation at the spacer is applied

Hydrothermal dissolution of biomass and gasification to hydrogen

Biomass is a term for all organic materials that stem from plants. It has wide applications as a source of fuel and as a raw material for different chemical stocks. A method in which hydrogen fuel is produced from renewable biomass is proposed. Hydrogen can subsequently be used as a feed for fuel cells to generate electricity. It can also be applied in other energy producing processes. The developed method makes advantage of the reactivity of water under hot, compressed environment.Dissolution of willow as a model compound representing biomass was studied in 200-350°C temperature range. A 95% dissolution of willow was achieved. Lignin and hemicellulose in willow were fragmented and dissolved at a temperature of 200°C and at a pressure of 100 bar (10 MPa). Cellulose was dissolved at 320°C. Rapid hydrolysis of lignin, hemicellulose and cellulose to oligomers and glucose is proposed as the evolution mechanism. Recondensation behavior of the dissolved oligomers was identified as the main challenge for dissolution. A continuous flow process for dissolution was found effective in this regard.The process of converting biomass-derived compounds into gases was also studied. Glucose was used as a model compound to characterize the chemistry of biomass gasification. Successful gasification of 0.1 M glucose solution to a mixture of H2, CO2 and CH4 gas was achieved by using Pt/Al2O3 as a catalyst. Qualitative analyses of liquid residues showed that the main decomposition products in the liquid phase were alcohols and carboxylic acids. Concentrated glucose solutions were found to be reactive forming undesired precipitates during gasification. This was found to be problematic in the catalytic gasification process. A new processing concept and a new reactor design were proposed to solve this problem.Findings presented in this thesis showed that hot, compressed water provided an alternative to corrosive chemicals and toxic solvents, facilitating utilization of biomass as a source of renewable fuel and as a source of chemical stocks

Fabrication of thermal barrier coating using electrochemical methods

An electrochemical method of fabrication of (NiCoCrAlY)/MgO/Yttria stabilized zirconia (YSZ) multilayered coating was proposed. This multilayered coat is expected to work as a thermal barrier coating (TBC) for nickel superalloy substrates. The (NiCoCrAlY) layer was deposited using the electrophoretic deposition technique, the MgO layer was deposited by the electrolytic deposition technique and the YSZ layer was electrophoretically deposited.In order to study the deposit morphology and to determine the appropriate processing parameters for the multilayered coat, one-layer coatings of (NiCoCrAlY), MgO and YSZ were deposited and characterized. At first, the process of depositing (NiCoCrAlY) alloy particles using an aqueous media with AlCl3 or Al(NO3)3 as an electrolyte revealed that the alloy particles were deposited at the same time as aluminium oxide. The co-deposited aluminium oxide worked as a binder between the particles and the substrate.In the electrolytic deposition process of the MgO coating, the layer deposited from Mg(NO3)2 solution was mainly magnesium hydroxide and it had to be calcinated to form a MgO coating. An optimization of the deposition process demonstrated that a crack free deposit of MgO could be obtained at low current density.An optimum condition of the electrophoretic deposition process was established for YSZ; it was found that adding 5% water to the acetone bath increased the deposition rate of the YSZ particles, and had increased the porosity in the coat.A composite coating of (NiCoCrAlY)/MgO was formed after heat treatment at 850°C for 1 hr. The electrochemically deposited MgO was easily sintered at 850°C, which resulted in a dense ceramic coating that protects the substrate and the (NiCoCrAlY) coating from oxidation during sintering of the electrophoretically deposited YSZ layer at 1100°C

Breaking and Connecting: Highly Hazy and Transparent Regenerated Networked-Nanofibrous Cellulose Films via Combination of Hydrolysis and Crosslinking

High optical transparency combined with high optical haze are essential requirements for optoelectronic substrates. Light scattering caused by haze is responsible for increasing light harvesting in photon-absorbing active materials, hence increasing efficiencies. A trade-off between transparency and haze is common in solar substrates with high transparency (~90%) and low optical haze (~20%), or vice versa. In this study, we report a novel, highly transparent film fabricated from regenerated cellulose after controlled acid-hydrolysis of microcrystalline cellulose (MCC). The developed networked-nanofibrous cellulose was chemically crosslinked with glutaraldehyde (GA) and vacuum-cured to facilitate the fabrication of mechanically stable films. The effects of crosslinker concentration, crosslinking time, and curing temperature were investigated. Optimum conditions for fabrication unveils high optical transparency (~94%) and high haze (~60%), using 25% GA for 24 hr with a curing temperature of 25 °C; therefore, conveying an optimal substrate for optoelectronics applications. The high haze arises primarily from the crystalline, networked crystals of cellulose II structure formed within the regenerated cellulose upon hydrolysis. Moreover, the developed crosslinked film presents high thermal stability, water resistance, and good mechanical resilience. This high-performance crosslinked cellulose film can be considered a potential material for new environmentally-friendly optical substrates

Facile morphological tuning of thin film composite membranes for enhanced desalination performance

Abstract Polyamide (PA) membranes with a thin selective layer have been widely investigated for desalination and water treatment. Several modifications have been proposed over the years to tailor the morphology of such thin film composite (TFC) membranes by altering the support and/or selective layers to achieve superior performance. In this study, a facile approach towards fabricating a highly wrinkled selective layer has been demonstrated through bio-inspired modification of the support layer with Y-type zeolites. Results showed that incorporating zeolites in a smaller dimension (200 nm) produced by a unique ball milling technique is favorable for a defect-free selective layer in comparison to larger commercial zeolites. PA membranes formed by the interfacial polymerization (IP) of Piperazine (PIP) and 1,3,5-Benzenetricarbonyl trichloride (TMC) revealed highly wrinkled morphology due to the presence of zeolites in the TFC interlayer. At optimum fabrication conditions, the membrane exhibited a fast transport of 22.5 ± 2.2 Lm-2h-1bar-1 with a salt rejection of 48.6, 91.3, 99.1, and 99.5% for NaCl, MgCl2, MgSO4, and Na2SO4, respectively. Besides the unique preparation of zeolites in smaller dimensions, the novelty of this study lies in the facile membrane pretreatment before IP to achieve wrinkled PA membranes for enhanced nanofiltration performance

Barriers to Innovation in Water Treatment

While phenomenal strides are being made on the technological front, the water industry lags behind other sectors in the adoption of innovative techniques. Contributing factors include long lifetimes and costs of previous water infrastructure, risk aversion due to public health concerns surrounding water access, and low financing for innovation. While many professionals see the need for innovation, they prefer traditional tried and tested routes. Regulations may be useful in accelerating the transition to sustainable technologies. Furthermore, the literature emphasizes the role of environmental, social, and political actors, as well as their interplay in realizing innovation in the water sector