Synthesis, characterization, and application of CoFe 2 O 4 @amino‐2‐naphthol‐4‐sulfonic acid as a novel and reusable catalyst for the synthesis of spirochromene derivatives (original) (raw)
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Membranes, 2021
In order to overcome the challenges of low permeate flux (Jp) and the accompanying reverse solute flux (JS) during the forward osmosis (FO) membrane separation process, we synthesized four hybrid materials of polyacid-based organic compounds and incorporated them into the selective polyamide (PA) layer to make novel thin-film nanocomposite (TFN) FO membranes. The Jp and JS of each membrane were evaluated and used along with membrane selectivity (Jp/JS) as indicators of membrane separation performance. The fabricated and modified membranes were also characterized for ridge and valley surface morphologies with increasing hydrophilicity and finger-shaped parallel channels in the PSf substrate. Moreover, two highly hydrophilic nanoparticles of graphene oxide (GO) and titanium oxide (TiO2) were introduced with the hybrid materials for PA modification, which can further enhance the Jp of the TFN membranes. The highest Jp of the TFN membranes achieved 12.1 L/m2-h using 0.1% curcumin-acetog...
Polymers
In the present work, the novel dense and supported membranes based on polyvinyl alcohol (PVA) with improved transport properties were developed by bulk and surface modifications. Bulk modification included the blending of PVA with chitosan (CS) and the creation of a mixed-matrix membrane by introduction of fullerenol. This significantly altered the internal structure of PVA membrane, which led to an increase in permeability with high selectivity to water. Surface modification of the developed modified dense membranes, based on composites PVA-CS and PVA-fullerenol-CS, was performed through (i) making of a supported membrane with a thin selective composite layer and (ii) applying of the layer-by-layer assembly (LbL) method for coating of nano-sized polyelectrolyte (PEL) layers to increase the membrane productivity. The nature of polyelectrolyte type-(poly(allylamine hydrochloride) (PAH), poly(sodium 4-styrenesulfonate) (PSS), poly(acrylic acid) (PAA), CS), and number of PEL bilayers (2-10)-were studied. The structure of the composite membranes was investigated by FTIR, X-ray diffraction, and SEM. Transport properties were studied during the pervaporation separation of 80% isopropanol-20% water mixture. It was shown that supported membrane consisting of hybrid layer of PVA-fullerenol (5%)-chitosan (20%) with five polyelectrolyte bilayers (PSS, CS) deposited on it had the best transport properties.
Polymer Membranes for Sustainable Technologies
Membrane-based processes have found wide acceptance and are used as powerful alternatives for conventional techniques such as distillation, extraction, or energy production. Frequently, membranes prepared from commodity polymers do not have the desired properties for the various applications. For example, fouling is still an unsolved problem in membrane applications, which is closely related to surface properties of both the membrane and the foulant. To meet the requirements for the various tasks, membranes with tailor-made properties are needed. In this contribution on the one hand surface modification techniques are described, which are used to (a) obtain microfiltration membranes with low-fouling tendency and (b) to prepare membranes with required properties in pervaporation separation applications. On the other hand modification/functionalization of polymers for use as ion-exchange membranes in energy-producing systems (fuel cells) are discussed. The focus is set on surface modification with polyelectrolytes and polyelectrolyte multilayer systems. This versatile technique enables the preparation of porous membranes with adjustable surface charge and low-fouling tendency without interference of permeate quality. Dense pervaporation membranes based on polyelectrolyte multilayer systems, with high selectivities and moderately high flux were obtained. The performance of such membranes can be controlled by the polyelectrolytes used (charge density) and the preparation conditions (e.g. temperature). Finally, a short introduction of new membrane materials based on fully aromatic polymers as alternatives to perfluoroalkylsulfonic acids, such as Nafion, is given.
Polymers
In this work, dense and supported pervaporation polyvinyl alcohol (PVA)-based membranes modified with poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate)(PSS)/PAH top nanolayers were synthesized. Two main points were investigated: the role of the polyelectrolyte PAH on water selectivity of the selective polymer matrix and the impact of the porous substrate based on polyacrylonitrile (PAN) and aromatic polysulfone amide (UPM-20®), used to get supported high-performance membranes. Various methods of analysis (fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), porosity, contact angles, ultrafiltration) were applied to study the developed membranes. Transport characteristics of the developed membranes were studied in isopropanol dehydration by pervaporation. Obtained results are discussed in the light of the structure and physicochemical characteristics of these PVA/...
Journal of Water Process Engineering, 2019
Forward osmosis (FO) has emerged as a novel membrane-based separation method for application for wastewater treatment, seawater desalination,and sustainable energy. A major challenge in the development of forward osmosis process is the lack of a high-efficiency membrane. In this study, a next-generation membrane for FO process was investigated by integrating nanotechnology with membrane science. Incorporation of polyoxometalate based open frameworks (POM-OFs) within the polyamide (PA) active layer of thin film composite (TFC) membrane has generated a new type of thin film nanocomposite (TFN) membrane with significantly enhanced hydrophilicity and permeability properties. The successful incorporation of the POM-OFs in the membranes active layer was investigated through Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. The water flux of POM-OFs modified membrane (TFN w3 , containing 500 ppm of POM-OFs) in FO and PRO modes was 29.9 and 41.7 LMH, the value of which was about two times those of TFC membrane. In conclusion, we report a novel forward osmosis membrane for wastewater treatment.
Membranes
This study presents the preparation of hybrid nanofiltration membranes based on poly(1,4-phenylene ether ether sulfone), polyacrylonitrile, poly(vinyl pyrrolidone), and SBA-15 mesoporous silica. Laser treatment of polymeric solutions to enhance the hydrophilicity and performance of membranes was investigated. The membranes’ structure was characterized using scanning electron (SEM) and atomic force (AFM) microscopy and contact angle measurements. The addition of PAN in the casting solution produced significant changes in the membrane structure, from finger-like porous structures to sponge-like porous structures. Increased PAN concentration in the membrane composition enhanced the hydrophilicity of the membrane surface, which also accounted for the improvement in the antifouling capabilities. The permeation of apple pomace extract and the content of polyphenols and flavonoids were used to evaluate the efficacy of the hybrid membranes created. The results showed that the hybrid nanofil...
Polymers
The commercial thin-film composite (TFC) nanofiltration (NF) membrane is unsuitable for engineered osmosis processes because of its thick non-woven fabric and semi-hydrophilic substrate that could lead to severe internal concentration polarization (ICP). Hence, we fabricated a new type of NF-like TFC membrane using a hydrophilic coated polyacrylonitrile/polyphenylsulfone (PAN/PPSU) substrate in the absence of non-woven fabric, aiming to improve membrane performance for water and wastewater treatment via the engineered osmosis process. Our results showed that the substrate made of a PAN/PPSU weight ratio of 1:5 could produce the TFC membrane with the highest water flux and divalent salt rejection compared to the membranes made of different PAN/PPSU substrates owing to the relatively good compatibility between PAN and PPSU at this ratio. The water flux of the TFC membrane was further improved without compromising salt rejection upon the introduction of a hydrophilic polydopamine (PDA)...