Selective Separation Of Water Research Articles

Fabrication and properties of asymmetric PET fabrics with high-permeation flux for on-demand oil/water separation

Indeed, it is yet to be achieved that finds a viable solution to the challenge of ever-growing and severe oil wastewater issues to meet easy operation and low cost. Herein, a facile strategy was proposed to fabricate asymmetric membranes via immobilizing poly (itaconic anhydride) (PITA) super-hydrophilic polymeric nanoparticles onto the surface of polyethylene glycol terephthalate (PET) nonwoven fabrics (PET-g-ITA) by surface precipitation photo-grafting (S2P) polymerization under ultraviolet (UV) light. The PET-g-ITA membrane displayed in an asymmetry mode mainly attributed to the UV shield feature of PET. Subsequently, the asymmetric PET-g-ITA membrane was hydrolyzed in an alkaline solution to enable the UV-illuminated side with superior hydrophilicity (WCA∼0°) and underwater superoleophobicity (UOCA∼153°). It exhibited outstanding performance in the selective separation of water and light/heavy oil. In water removal mode, the water/n-hexane mixture exhibited notably high permeation flux (94,562 ± 4948 L m-2 h-1) and high separation efficiency (99.8 %) for water. Meanwhile, the water/dichloromethane mixture also showed remarkably high permeation flux (76,238 ± 8949 L m-2 h-1) and separation efficiency (94.5 %) for dichloromethane in oil removal mode. More interestingly, these membranes could almost restore their oil/water performance to that of the primary membrane after cleaning. All separation processes are handled by energy-efficient gravity-driven separation methods, providing a competitive route for on-demand water and light/heavy oil separation.

Selective separation of water and methanol from hydrogen and carbon dioxide at elevated temperature through polyimide and polyimidazole based membranes

Methanol (CH3OH) produced by carbon dioxide (CO2) hydrogenation represents a compelling strategy to generate a viable hydrogen (H2) carrier for energy storage and transportation, while mitigating carbon emissions from industry. The CO2 hydrogenation reaction suffers from a lower thermodynamic equilibrium compared to the conventional syngas route to methanol, and as such there is significant recycling of reagents. A membrane reactor (MR) configuration is ideally suited to overcome this equilibrium limitation if the products (CH3OH and H2O) can be selectively removed. However, the presence of H2 require non-porous polymeric membranes to achieve this selectivity, which represents a challenge given the elevated temperatures required for catalyst functionality. Here, three thermally resilient glassy polymeric membranes (two polyimides and polybenzimidazole) were investigated for their permselectivity towards CH3OH and H2O at temperatures from 100 to 200 °C under pressurized conditions. The permeability for both vapours were demonstrated to be solubility dependent for the three membranes over the temperature and activity ranges studied. This enabled all three membranes to demonstrate selectivity for CH3OH and H2O, compared to CO2 and H2, under single and mixed gas conditions. The greatest permeability and selectivity were for H2O in each polymer, due to this vapor's high condensability and small kinetic diameter, with permeability decreasing with temperature. Correspondingly, selectivity against H2 and CO2 decreased with temperature, as these lighter gas' permeability increased with temperature, but selectivity for the vapours was retained. As such, the high fractional free volume polyimide membrane represents the most suitable candidate for a CO2-hydrogenation MR.

MXene: A two-dimensional material in selective water separation via pervaporation

MXene, well-identified as Ti 3 C 2 T X , belongs to the family of two-dimensional (2D) materials, which have been currently explored in various applications. Very recently, such materials have been pointed out as potential nanomaterials for advanced solute separations when introduced in membranes, such as ion separation, gas separation, nanofiltration, chiral molecular separation, and solvent separation. This latter separation, generally named Pervaporation (PV), is identified as a highly selective technology for water separations. To date, few pieces of research have been released but providing interesting insights into several solvent (including water) separations. Hence, this brief review aims to analyze and discuss the latest advances for utilizing MXenes for PV membranes. Particular emphasis has been devoted to the relevant outcomes in the field, along with the strategies followed by researchers to tailor membranes. Based on the current findings, the perspectives in the field are also stated.

Natural zeolite clinoptilolite-phosphate composite Membranes for water desalination by pervaporation

Natural zeolite membranes, directly sectioned from mineral deposits, have been previously reported to show molecular sieve characteristics in selective separation of water and hydrated cations. Although a high removal of cations was observed, the low water flux was a limitation for any potential industrial applications. In this study novel clinoptilolite-based phosphate composite membranes were prepared by dry pressing of mixed powder materials followed by high temperature autoclave steaming and characterized by XRD, SEM-EDX. Their performance for pervaporative water desalination was examined using different levels of salinity in a temperature range of 25–95°C and feed side pressure of 1atm. At 1400ppm Na feed salinity and 95°C, a water flux of 15kg/m2h and over 95% removal of Na+ were obtained. The water flux achieved was about 10 times higher than the flux obtained using natural zeolite rock membranes. Introducing phosphate into the composite membranes appears to provide not only mechanical strength, through the possible chemical bonding between zeolite particles and the in-situ phosphate cement, but also to create a chemically favorable interface between zeolite crystals. Such interface might facilitate the desalination process bypassing the technical difficulties of ion leakage/diffusion through the inter-crystal spaces commonly associated with synthetic zeolite membranes.

Selective Separation of Water, Methanol, and Ethanol by a Porous Coordination Polymer Built with a Flexible Tetrahedral Ligand

A novel porous coordination polymer, Cu(II)(mtpm)Cl(2) [mtpm = tetrakis(m-pyridyloxy methylene)methane], has been synthesized, and its crystal structure has been determined. Its adsorption isotherms for water, methanol, and ethanol are totally different from each other. It adsorbs water at low humidity and shows gate-open behavior for methanol, but it does not adsorb ethanol. This compound has the capacity to separate both methanol and water from bioethanol, which is a mixture of water, methanol, and ethanol.

Experiment and modeling of advanced ozone membrane reactor for treatment of organic endocrine disrupting pollutants in water

An advanced ozone membrane reactor that uses membranes for ozone distribution, reaction contact and selective water separation was used for ozone treatment of a recalcitrant endocrine disrupting compound in water. Experiments and model calculation were employed to examine the ozonation of phthalate in the new reactor. Experimental results showed that fast ozone mass transfer rate is responsible for membrane reactor's superb performance compared with a semibatch reactor. Selective water removal further enhanced phthalate conversion and TOC removal by concentrating the pollutants in the reaction zone. Clean water was produced by membrane separation. Mathematical model was used to investigate the effect of membranes, reactor design and reaction operation on pollutant conversion and removal.

Adsorptive separation of liquid water/acetonitrile mixtures

Twenty-nine adsorbents of different adsorbent classes, compromising zeolites, activated carbon, silicagel and metal–organic frameworks (MOF) were tested in batch adsorption experiments with liquid water/acetonitrile mixtures. Their performance in the selective separation of water from acetonitrile (ACN) was evaluated by analyzing these experimental batch isotherm data with a breakthrough model. Water isotherms (296 K) and diffusion coefficients of both water and ACN are presented for promising adsorbents. 4A zeolite was identified as a suitable adsorbent; it allowed successful fixed bed adsorption column separation of liquid water/acetonitrile mixtures with water contents up to 40 wt.%. The breakthrough curves were compared to numerical and analytical models for fixed bed adsorption, using independently determined diffusion and adsorption equilibrium parameters.

Separation of Aqueous Ethanol Solution by Pervaporation using Uniplanar-Oriented Carboxymethyl Cellulose Membranes

Uniplanar Oriented carboxymethyl cellulose (CMC) membranes were prepared by the simultaneous-biaxial (SB) stretching method under swollen conditions in the wet process, where CMC molecules were randomly oriented within the membrane along parallel to the membrane surface, as reported previously. Then, separation of aqueous ethanol solutions by pervaporation through the uniplanar-oriented CMC membranes was investigated. Permeation rates (flux) of the uniplanar-oriented CMC membranes were considerably higher than those of unstretched membranes. On the contrary, separation factors decreased with increasing degree of uiplanar orientation. Furthermore, the effect of uniplanar orientation on pervaporation was discussed in relation to molecular structure of CMC and affinity of the CMC membranes to ethanol and water. CMC-H and CMC-H-SB membranes were prepared by converting CMC-Na and CMC-Na-SB to their H-type in aqueous ethanol solution. Similarly, CMC-Li. CMC-K, CMC-Li-SB and CMC-K-SB membranes were prepared from CMC-Na and CMC-Na-SB. These membranes were effective in selective separation of water from aqueous ethanol solutions by the pervaporation technique. Particularly, in the case of CMC-Na-SB membranes, the flux was similar to that of CMC-Na membranes, but permeation of ethanol from the aqueous ethanol solutions was not observed.

Selective separation of water from aqueous alcohol mixtures through functionalized syndiotactic poly(styrene‐co‐4‐methylstyrene) membranes by pervaporation

AbstractThe pervaporation performances of a series of functionalized syndiotactic poly(styrene‐co‐4‐methylstyrene) (SPSM) membranes for various alcohol mixtures were investigated. The syndiotactic polystyrene copolymers, poly(styrene‐co‐4‐methylstyrene) (SPSM), were prepared by styrene with 4‐methylstyrene using a Cp*Ti(OCH3)3/methyl aluminoxane (metallocene/MAO) catalyst. The effect of functionalization on the thermal properties and polymer structure of the SPSM membranes were also investigated. The crystallinity of the functionalized SPSM membrane is lower than that of the unfunctionalized SPSM membranes. The water molecules preferentially permeate through the SPSM membranes. Compared with unfunctionalized SPSM membranes, the functionalized SPSM membrane effectively increases the membrane formation performances and the pervaporation performances. The optimun pervaporation performance (a separation factor of 510 and permeation rate of 220 g/m2h) was obtained by the bromination of SPSM (SPSMBr) membrane with a 90 wt % aqueous ethanol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2247–2254, 2002

Selective separation of water from aqueous alcohol solution through fluorine-containing aromatic polyamide membranes by pervaporation

For dehydrating aqueous alcohol solution by pervaporation, a fluorine-containing aromatic polyamide membrane was synthesized. The fluorine-containing polyamides were prepared by direct polycondensation of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, BAPPH, with various aromatic diacids by triphenyl phosphite and pyridine in N-methyl-2-pyrrolidinone. The novel aromatic polyamides were examined by elemental analysis, FTIR, and X-ray diffraction. The aromatic polyamides were crystalline except (A-B 2). The effects of feed composition, degree of swelling, and the molecular size of alcohols on pervaporation performances were investigated. Water molecules preferentially permeate through the aromatic polyamide membranes. A separation for water of 36 and a 383 g/m 2h permeation rate with a 90 wt% feed ethanol concentration was obtained.

Pervaporation of aqueous acetic acid mixture through poly(acrylic acid-co-acrylonitrile) membranes

Separation of aqueous acetic acid mixtures through a membrane was carried out by pervaporation. A membrane made from poly(acrylic acid-co-acrylonitrile) was effective in the selective separation of water from acetic acid/water mixtures by pervaporation.

Application and development of synthetic polymer membranes. VI. Pervaporation of aqueous ethanol solution through quaternized poly[3‐(N′,N′‐dimethyl) aminopropylacrylamide‐co‐acrylonitrile] membranes

AbstractMembranes obtained from polymers, quaternized poly[3‐(N′,N′‐dimethyl) aminopropylacrylamide‐co‐acrylonitrile]s, showed selective separation of water from aqueous ethanol solution by pervaporation. The separation factor toward water reached over 15,000. Membrane performance showed a good correlation to membrane polarity. Differential scanning calorimetric melting endotherms of the water‐swollen membranes were studied to clarify the state of water in the membranes. The results suggested that there are two states of water in the membrane: bound and free. The higher the fraction of bound water in the membrane, clearly, the more preferentially was water permeated.

Selective separation of water from water–ethanol solution through quarternized poly(4‐vinylpyridine‐co‐acrylonitrile) membranes by pervaporation technique

AbstractPolymer membranes having cationic charge site, poly(1‐alkyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (alkyl: methyl, butyl, or octyl) were prepared in terms of coulombic interaction for separation of water–ethanol mixtures. The incorporation of cationic charge site into the membrane led to improve not only separation factors (selectivity toward water) but also flux number in the separation of aqueous ethanol solution by pervaporation technique. Target values, which were requested to have from the viewpoint of industrial utilization for separation of aqueous ethanol solution were attained as follows: separation factor toward water over 50 and flux value over 500 g m−2 h−1, through poly(1‐methyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (membrane 3) (quarternized fraction of pyridinium moiety, 89.5%; mol fraction of pyridinium moiety, 0.034) and poly(1‐butyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (membrane 5) (quarternized fraction, 100%; mol fraction of pyridinium moiety, 0.038). It was found that the introduction of cationic charge site into the membrane was one of feasible methods to obtain suitable membranes for water permselective membranes in the separation of water–ethanol mixtures.

Synthesis of Poly{1-(2-methylpropenoyloxy)phthalimide-co-acrylonitrile} and the Selective Separation of Water and Ethanol through Its Membranes

A new polymer, poly{1-(2-methylpropenoyloxy)phthalimide-co-acrylonitrile} (Poly(1-co-2)) was synthesized based on molecular designs for the separation of water and ethanol. The sequence distribution of the copolymers were investigated by 13C NMR spectroscopy. A terminal model was used to interpret the propagation process in the copolymerization. The reactivity ratios in the solution polymerization at 45°C were evaluated as r1=1.90 and r2=0.39. Radical reactivity indices and frontier electron densities were calculated. The membrane prepared from this copolymer carried out a selective separation of water from aqueous ethanol solution by pervaporation method. The separation factor toward water was as high as 1200.

Separation of water-acetic acid mixture by pervaporation through synthetic polymer membranes containing pendant carboxylic acid.

Separation of water-acetic acid mixture through a membrane was carried out. Membranes obtained from poly (acrylic acid-co-acrylonitrile) and poly (acrylic acid-co-styrene) were effective for a selective separation of water from aqueous acetic acid solution by means of pervaporation method. Permeation of water and acetic acid through membranes from poly (acrylic acid-co-acrylonitrile) was interpreted by a carrier mechanism, in which carboxylic acid moiety in the membrane played a role as a fixed carrier for both permeates. Water was permeated through poly (acrylic acid-co-styrene) membranes by TYPE II mechanism, in other words, an all or nothing mechansim, while acetic acid was permeated without having any specific interaction with the membrane.