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Svetlana V Kononova, Elena V Kruchinina, Valentina A Petrova, Yulia G Baklagina, Vera V Klechkovskaya, Anton S Orekhov, Elena N Vlasova, Elena N Popova, Galina N Gubanova, Yury A Skorik
Self-supporting multilayer films containing a polyelectrolyte complex (PEC) were prepared by the sequential layering of sodium hyaluronate (HA, MW 5.4 × 104 ) and chitosan (CS, MW 1.6 × 105 , the degree of deacetylation 0.80) in different orders. Imaging with low-voltage scanning electron microscopy (LVSEM) showed that the CS/HA films had a multilayer structure, while X-ray diffraction (XRD) indicated significant structuring of the CS layer near the PEC-CS region. Analysis of the thermal properties of the CS/HA films revealed differences in the structural organization and morphological features of the polymer layers and high thermal stability of the PEC layer...
April 1, 2019: Carbohydrate Polymers
Haoli Zhou, Wanqin Jin
Microporous polymer membranes have been widely studied because of their excellent separation performance. Among them, polymers of intrinsic micro-porosity (PIMs) have been regarded as a potential next-generation membrane material for their ultra-permeable characteristics and their solution-processing ability. Therefore, many reviews have been reported on gas separation and monomers for the preparation of PIMs. This review aims to provide an overview of the structure-solubility property. Different structures such as non-network and network macromolecular structure made of different monomers have been reviewed...
December 26, 2018: Membranes
G Polotskaya, A Pulyalina, M Goikhman, I Podeshvo, V Rostovtseva, S Shugurov, I Gofman, N Saprykina, N Gulii, N Loretsyan, A Toikka
Polymer membranes with improved transport properties are required for effective separation of organic mixtures (such as methanol‒hexane system) by combination of pervaporation and azeotropic distillation. The present work is devoted to comparative study of two types of membranes based on poly(amidoimide acid) with 2,2'-biquinoline-6,6' units in the backbone; the objects were prepared (i) from the initial polymer and (ii) from the polymer-metal complex (with Cu(I)). Thermo-mechanical and mass spectrometric investigations demonstrated good operational properties of the samples...
December 14, 2018: Scientific Reports
Essyllt Louarn, Abdoul Monem Asri-Idlibi, Julien Leprovost, Michel Héninger, Hélène Mestdagh
Membrane Inlet Mass Spectrometry (MIMS) was used to analyze monochloramine solutions (NH₂Cl) and ammonia solutions in a compact FTICR. Chemical ionization enables identification and quantification of the products present in the permeate. The responses of protonated monochloramine and ammonium increase linearly with the solution concentration. The enrichments were respectively 1.2 and 5.5. Pervaporation is dependent on pH and only the basic form of ammonia NH₃ pervaporates through the membrane. Unexpectedly, the small ammonia molecule permeated very slowly...
December 3, 2018: Sensors
Mahdi Nikbakht Fini, Sepideh Soroush, Mohammad Mehdi Montazer-Rahmati
In the present work, ceramic-supported chitosan hybrid membranes were prepared for the pervaporation dehydration of ethanol. Mullite and combined mullite-alumina (50% alumina content) tubular low-cost ceramic supports were fabricated, and their influence on membrane performance was compared to a commercial α-alumina support. The membrane preparation parameters were different ceramic supports and the concentration of chitosan solution (varying from 2 wt.% to 4 wt.%). The supports and hybrid membranes were characterized by field emission scanning electron microscopy (FE-SEM) and contact angle measurements...
November 30, 2018: Membranes
Zishu Cao, Shixuan Zeng, Zhi Xu, Antonios Arvanitis, Shaowei Yang, Xuehong Gu, Junhang Dong
The tremendous potential of zeolite membranes for efficient molecular separation via size-exclusion effects is highly desired by the energy and chemical industries, but its practical realization has been hindered by nonselective permeation through intercrystalline spaces and high resistance to intracrystalline diffusion in the conventional zeolite membranes of randomly oriented polycrystalline structures. Here, we report the synthesis of ZSM-5 zeolite nanosheets with very large aspect ratios and nanometer-scale thickness in the preferred straight channel direction...
November 2018: Science Advances
Michael Z Hu, Chaiwat Engtrakul, Brian L Bischoff, Mi Lu, Mussie Alemseghed
Surface wettability-tailored porous ceramic/metallic membranes (in the tubular and planar disc form) were prepared and studied for both vapor-phase separation and liquid pervaporative separations of water-ethanol mixtures. Superhydrophobic nanoceramic membranes demonstrated more selective permeation of ethanol (relative to water) by cross-flow pervaporation of liquid ethanol⁻water mixture (10 wt % ethanol feed at 80 °C). In addition, both superhydrophilic and superhydrophobic membranes were tested for the vapor-phase separations of water⁻ethanol mixtures...
October 12, 2018: Membranes
Yamini Satyawali, David Fernandes Del Pozo, Pieter Vandezande, Ingmar Nopens, Winnie Dejonghe
Hydrophobic pervaporation (PV), allowing for the separation of an organic component from an aqueous stream, was investigated for in situ acetone removal from a transamination reaction. A poly(dimethylsiloxane) membrane was applied in a coupled enzymatic process at 5 L scale. Among the four components, there was no loss of donor and product amines through PV which was highly desirable. However, in addition to removal of acetone, there was also an unwanted loss of acetophenone (substrate ketone) because of PV...
October 13, 2018: Biotechnology Progress
Changlong Zou, Li-Chiang Lin
Molecular dynamics simulations are employed to demonstrate the potential of zeolite nanosheets as pervaporation membranes for ethanol extraction. Our results show that zeolite nanosheets can provide orders of magnitude higher fluxes compared to currently available membranes and achieve outstanding separation factors. The dominant role of membrane surfaces in determining the separation performance is also identified and explored at an atomic level. Developing nanosheet membranes with hydrophobic surfaces and/or with a minimal surface silanol density represents the keys to enable highly selective separation processes...
November 22, 2018: Chemical Communications: Chem Comm
Xiaocao Wu, Wan Wei, Jianwen Jiang, Jürgen Caro, Aisheng Huang
Separation of p-xylene (kinetic diameter ca. 0.58 nm) from its bulkier isomers (o-xylene and m-xylene, ca. 0.68 nm) is challenging, but important in the petrochemical industry. Herein, we developed a highly selective and stable metal-organic framework (MOF) MIL-160 membrane for selective separation of p-xylene from its isomers by pervaporation. The suitable pore size (0.5∼0.6 nm) of the MIL-160 membrane selectively allows p-xylene to pass through, while excluding the bulkier o-xylene and m-xylene. For the separation of equimolar binary p-/o-xylene mixtures at 75 °C, high p-xylene flux of 467 g m-2  h-1 and p-/o-xylene selectivity of 38...
September 24, 2018: Angewandte Chemie
Thomas La Rocca, Emilie Carretier, Thomas Clair, Martial Etienne, Philippe Moulin
The regeneration of volatile organic solvents via dehydration tests, from 90 wt %, was evaluated by pervaporation using an on-line near-infrared (NIR) spectrometer. Experiments were performed using a bis(triethoxysilyl)methane (BTESM)-based ceramic HybSi® membrane at temperatures of 20, 30 and 40 °C. The presence of an on-line NIR allows continuous monitoring of the process without sampling, and quickly estimates mass fractions of species in the retentate. Dehydration tests were performed at 30 °C in order to confirm the on-line NIR reproducibility, and closely matched results obtained with an off-line densimeter...
September 4, 2018: Membranes
Zongli Xie, Derrick Ng, Manh Hoang, Jianhua Zhang, Stephen Gray
Desalination by pervaporation is a membrane process that is yet to be realized for commercial application. To investigate the feasibility and viability of scaling up, a process engineering model was developed to evaluate the energy requirement based on the experimental study of a hybrid polyvinyl alcohol/maleic acid/tetraethyl orthosilicate (PVA/MA/TEOS) Pervaporation Membrane. The energy consumption includes the external heating and cooling required for the feed and permeate streams, as well as the electrical power associated with pumps for re-circulating feed and maintaining vacuum...
September 3, 2018: International Journal of Environmental Research and Public Health
Decai Yang, Dongxu Tian, Chuang Xue, Fei Gao, Yang Liu, Hong Li, Yongming Bao, Jingjing Liang, Zongbin Zhao, Jieshan Qiu
Synthetic membranes usually suffer from a ubiquitous trade-off between permeability and selectivity. Carbon nanotube (CNT)-based hybrid materials have shown attractive properties in high-performance membrane preparation; however, the aggregation of random CNTs in polymer remains a great challenge. Herein, the aligned and open-ended CNT/(polydimethylsiloxane) PDMS membranes are controllably fabricated to form a hamburger-like structure that possesses nanochannels (∼10 nm) in the intermediate layer as well as angstrom cavities in the embedded PDMS...
October 10, 2018: Nano Letters
Ebrahim Ataeivarjovi, Zhigang Tang, Jian Chen
In this present work, a novel approach has been proposed by which a solvent absorption and membrane desorption methods can significantly reduce the carbon dioxide (CO2 ) emission and energy consumption. In this method, the CO2 capture processing is based on the combination of membrane and physical solvent. Here, dimethyl carbonate and polydimethylsiloxane (PDMS)-SiO2 nanocomposite were used as the physical solvent and desorption membrane, respectively. However, the main focus of this research was on the CO2 desorption behavior of PDMS-SiO2 hybrid membrane...
August 29, 2018: ACS Applied Materials & Interfaces
Hoda Azimi, Arian Ebneyamini, F Handan Tezel, Jules Thibault
The pervaporation separation of organic compounds from acetone-butanol-ethanol (ABE) fermentation model solutions was studied using activated carbon (AC) nanoparticle-poly (dimethylsiloxane) (PDMS) mixed matrix membranes (MMM). The effects of the operating conditions and nanoparticle loading content on the membrane performance have been investigated. While the separation factor increased continuously, with an increase in the concentration of nanoparticles, the total flux reached a maximum in the MMM with 8 wt % nanoparticle loading in PDMS...
July 10, 2018: Membranes
Faten Hassan Hassan Abdellatif, Jérôme Babin, Carole Arnal-Herault, Laurent David, Anne Jonquieres
Membranes made from cellulose acetate grafted with imidazolium or ammonium ionic liquids (ILs) containing different anions were considered for ethyl tert-butyl ether biofuel purification by pervaporation. The new cellulosic materials were obtained after bromide (Br- ) exchange by different anions (Tf2 N- , BF4 - , AcO- ). IL structure-membrane property relationships revealed that the membrane properties were strongly improved by varying the anion structure, molecular size and hydrogen bonding acceptor ability β in the Kamlet-Taft polarity scale...
September 15, 2018: Carbohydrate Polymers
Weibin Liang, Lin Li, Jingwei Hou, Nicholas D Shepherd, Thomas D Bennett, Deanna M D'Alessandro, Vicki Chen
Composite membranes with defective metal-organic frameworks (MOFs) connect the emerging fields of MOF topological modification, MOF-polymer interfacial engineering and composite material functionalization. Although defective MOFs can be fabricated via thermal or chemical treatment, the relationship between hierarchical MOF structure and their performance in a polymeric membrane matrix has so far not been investigated. Here we show how a modulator fumarate-based MIL-53(Al) microwave synthesis process results in defective MOFs...
April 14, 2018: Chemical Science
Siddhartha Moulik, Vani Bukke, S Chandrasekhar Sajja, Sridhar S
Present work reports the synthesis of a novel Chitosan-Polytetrafluoroethylene composite membrane with solvent resistant property for efficient separation of methanol/toluene mixture by pervaporation. The composite was crossed with tetraethyl orthosilicate (TEOS) to prevent or reduce membrane swelling and improve the separation factor. The synthesized membranes were characterized by SEM, FTIR and DSC analysis. Molecular dynamics (MD) simulation and computational fluid dynamics were coupled to predict the structural and diffusive properties besides concentration profile inside the membrane...
August 1, 2018: Carbohydrate Polymers
Ezra L Clark, Alexis T Bell
The electrochemical reduction of carbon dioxide is sensitive to electrolyte polarization, which causes gradients in pH and the concentration of carbon dioxide to form near the cathode surface. It is desirable to measure the concentration of reaction-relevant species in the immediate vicinity of the cathode because the intrinsic kinetics of carbon dioxide reduction depend on the composition of the local reaction environment. Meeting this objective has proven difficult because conventional analytical methods only sample products from the bulk electrolyte...
June 6, 2018: Journal of the American Chemical Society
Chao Zhu, Lijie Chen, Chuang Xue, Fengwu Bai
Background: Butanol derived from renewable resources by microbial fermentation is considered as one of not only valuable platform chemicals but alternative advanced biofuels. However, due to low butanol concentration in fermentation broth, butanol production is restricted by high energy consumption for product recovery. For in situ butanol recovery techniques, such as gas stripping and pervaporation, the common problem is their low efficiency in harvesting and concentrating butanol. Therefore, there is a necessity to develop an advanced butanol recovery technique for cost-effective biobutanol production...
2018: Biotechnology for Biofuels
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