Hydrophilic Support Research Articles

Preparation and characterization of thin film composite reverses osmosis membranes with wet and dry support layer

The aim of this work is to investigate the effect of initial conditions and properties of a support layer on the performance and structure of a thin film composite (TFC) polyamide membrane. For this purpose, four different polyethersulfone (PES) support layers were prepared and the polyamide layer was coated by interfacial polymerization over these support layers in wet and dry conditions. Surface properties and morphology as well as hydrophilicity of PES support membranes and TFC membranes were examined by atomic force microscopy, field-emission scanning electron microscope, attenuated total reflectance-FTIR, and contact angle analysis, respectively. The results showed that the initial conditions of the support layer had an important role in the performance and surface properties of TFC membranes. The TFC membrane, synthesized over a wet support membrane with larger pore size and more hydrophilicity, had more water flux and lower salt rejection. The effect of wet and dry conditions on the water flux was more significant when a less hydrophilic support layer was used. It was found that the effect of support layer hydrophilicity is more effective than its pore size in wet conditions on water flux of TFC membrane, while a different trend was observed at dry conditions.

Gold nanoparticles supported on modified red mud for biphasic oxidation of sulfur compounds: A synergistic effect

Gold nanoparticles were supported on the surface of three different matrixes based on red mud waste: (i) pure red mud, (ii) reduced red mud and (iii) partially carbon coated red mud, in order to produce different catalysts for desulfurization reactions. The catalysts were extensively characterized by X-ray diffraction, Mössbauer spectroscopy, thermogravimetric analyses, electron microscopies (SEM and TEM), energy dispersive spectroscopy (EDS) and BET surface area. Results showed that gold was successfully supported and distributed on the surface of red mud based materials as nanoparticles with diameters around 30nm. The catalyst prepared with carbon coated red mud has shown to be twice more efficient than others for biphasic desulfurization reactions. This result can be associated with its amphiphilicity, which allows the catalyst to be located on the interface of biphasic systems. In this position a synergistic effect occurs between gold nanoparticles that adsorb S containing molecules and red mud Fe sites that promote the formation of OH radicals. The same effect is not observed for catalyst with hydrophilic supports.

Hydrophilic nylon 6,6 nanofibers supported thin film composite membranes for engineered osmosis

Previous studies have concluded that an ideal thin film composite (TFC) membrane specially designed for Engineered Osmosis (EO) should have an ultra-thin selective layer with excellent permselectivity supported by a hydrophilic, highly porous, non-tortuous and thin support structure. In this study, an emerging TFC supporting material, electrospun nanofibers, were used to fabricate a TFC-EO membrane where the support structure and the selective layer properties were individually optimized. Specifically, nylon 6,6 nanofibers fabricated via electrospinning were used for the first time to form the support structure due to its intrinsic hydrophilicity and superior strength compared to other nanofiber materials. The resulting membrane exhibited half of the structural parameter of a regularly used commercial FO membrane. Furthermore, the selective layer permselectivity could be adjusted using a co-solvent during the interfacial polymerization processes. Adding acetone to the organic phase (hexane) was found to increase permeance and decrease selectivity and hence affect the osmotic flux performance of our membranes. Our best membrane outperformed the standard commercial FO membrane by exhibiting a 1.5 to 2 fold enhanced water flux and an equal or lower specific salt flux.

Direct Immobilization of Glucose Oxidase on the Hydrophilic Copolymer Support Containing Oxirane

Glucose oxidase (GOD) (EC 1.1.3.4) is an oxido-reductase that catalyses the oxidation action of glucose to hydrogen peroxide and D-glucono-δ-lactone [. GOD is widely used in the determination of free glucose in body fluids, in vegetal raw material and in the food industry [. It also has many applications in biotechnologies, typically enzyme assays for biochemistry including biosensors in nanotechnologies. Free GOD will be denatured and inactivated rapidly due to its structural instability under extreme pH or temperature [. Four immobilizing methods, including physical adsorption, covalent binding, crosslinking and embedding methods, were used to improve their economic feasibility. Covalent binding combined active functional group monomers of carriers onto enzymes [4-. Researches showed that oxirane groups can react with-NH2 and-HS of enzymes under mild conditions so that the enzyme molecules were immobilized on the copolymer support containing oxirane [.

Porous Al2O3/TiO2 tubes in combination with 1-ethyl-3-methylimidazolium acetate ionic liquid for CO2/N2 separation

The highest CO2 solubility and commercially-available ionic liquid, 1-ethyl-3-methylimidazolium acetate ([emim][Ac]), was immobilized in porous Al2O3/TiO2 tubes in order to study the potential of using supported ionic liquid membranes based on ceramic supports for CO2/N2 separation. The supported ionic liquid membranes (SILMs) were first prepared using a conventional immobilization procedure based on ionic liquid impregnation, and then, by coating the TiO2 mesoporous outer layer, reducing the membrane resistance to gas permeation.The permeation of these membranes to carbon dioxide and nitrogen was measured, yielding a CO2 permeance as high as PCO2=2.78±0.11×10−8mol/(m2sPa), with an ideal CO2/N2 selectivity of α(CO2/N2)=30.72±0.86 for membranes prepared under the coating procedure, which outperformed the state of the art for CO2/N2 separation in polymeric materials. The membrane stability tests demonstrated that the hydrophilic ceramic support was very effective for the immobilization of the liquid phase in the membrane for a period of 25h and at applied feed pressures of 4bar. Finally, the effect of water vapor in the gas stream and the effect of operation temperature on membrane separation performance were evaluated and compared.The high CO2 permeance values and comparable selectivity to polymeric materials may suggest the potential application of using Al2O3/TiO2 tubes in combination with [emim][Ac] ionic liquid for the selective removal/recovery of CO2 from a gas stream in industrial applications.

Synthesis and characterization of thin film nanocomposite forward osmosis membrane with hydrophilic nanocomposite support to reduce internal concentration polarization

Realizing that one of the most important challenges in the forward osmosis (FO) membrane is internal concentration polarization (ICP), thin film nanocomposite (TFN) membranes were prepared by incorporating different loadings of titanium dioxide (TiO2) nanoparticles (ranging from 0 to 0.90wt%) into the polysulfone (PSf) substrate in order to reduce ICP. The nanocomposite substrates prepared were characterized with respect to hydrophilicity, overall porosity, surface roughness and cross-sectional morphology by different methods. Results revealed that both hydrophilicity and porosity of the substrate were increased upon addition of TiO2 nanoparticles. Moreover, a large number of finger-like macrovoids were developed by increasing the loading of TiO2 nanoparticles, leading to enhancement in water permeability. As for the FO performance tested at AL-FS orientation and with DI water as feed and 0.5M NaCl as draw solution, the TFN membrane prepared using PSf substrate embedded with 0.60wt% TiO2 nanoparticles (designated as TFN0.60) exhibited the most promising result by showing water flux of 18.81L/m2h, i.e. 97% higher than the control TFC membrane prepared by substrate without TiO2 incorporation (designated as TFC), with no significant change in reverse solute flux. Compared to the control TFC membrane, the FO water flux of TFN0.60 was also reported to increase significantly from 4.2 to 8.1L/m2h (AL-FS orientation) and from 6.9 to 13.8L/m2h (AL-DS orientation) when seawater was used as feed solution and 2M NaCl was used as draw solution. The increase in water flux can be attributed to the decrease in structural parameter (S value=0.39mm), mainly due to the formation of finger-liked macrovoids that connect the top and bottom layer of the substrate and reduce the tortuosity, resulting in decreased ICP. Although further increasing TiO2 nanoparticles loading to 0.90wt% could increase membrane water permeability, the FO performance was compromised by a significant increase in reverse solute flux. To the best knowledge of the authors, this is the first report on TFN membrane using PSf-TiO2 nanocomposite substrate for FO applications.

Lipases immobilization for effective synthesis of biodiesel starting from coffee waste oils.

Immobilized lipases were applied to the enzymatic conversion of oils from spent coffee ground into biodiesel. Two lipases were selected for the study because of their conformational behavior analysed by Molecular Dynamics (MD) simulations taking into account that immobilization conditions affect conformational behavior of the lipases and ultimately, their efficiency upon immobilization. The enzymatic synthesis of biodiesel was initially carried out on a model substrate (triolein) in order to select the most promising immobilized biocatalysts. The results indicate that oils can be converted quantitatively within hours. The role of the nature of the immobilization support emerged as a key factor affecting reaction rate, most probably because of partition and mass transfer barriers occurring with hydrophilic solid supports. Finally, oil from spent coffee ground was transformed into biodiesel with yields ranging from 55% to 72%. The synthesis is of particular interest in the perspective of developing sustainable processes for the production of bio-fuels from food wastes and renewable materials. The enzymatic synthesis of biodiesel is carried out under mild conditions, with stoichiometric amounts of substrates (oil and methanol) and the removal of free fatty acids is not required.

Heterogeneous Silica‐Supported Ruthenium Phosphine Catalysts for Selective Formic Acid Decomposition

AbstractThe water‐soluble ruthenium(II)–mTPPTS complex (mTPPTS=meta‐trisulfonated triphenylphosphine) efficiently catalyzes the generation of hydrogen from formic acid in aqueous solution. This catalyst has been immobilized in a hydrophilic silica support to facilitate mobile portable applications. It was used in diluted formic acid solutions, in which the recycling of a liquid phase catalyst is problematic. A series of heterogenized catalysts have been prepared by the reaction of the ruthenium(II)–mTPPTS dimer and silica functionalized with diphenylphosphine groups via alkyl chains. The length of the alkylene chain separating the silica from the diphenylphosphine group has been varied in these catalysts—all of them catalyzing the decomposition of formic acid. The catalysts were easily separated from the solution and reused. The optimized catalytic system based on MCM41‐Si‐(CH2)2PPh2/Ru‐mTPPTS demonstrated an activity and stability comparable to those of the homogeneous catalyst: a turnover frequency of 2780 h−1 was obtained at 110 °C, and no ruthenium leaching was detected after turnover numbers of 71 000.

Pressure Retarded Osmosis and Forward Osmosis Membranes: Materials and Methods

In the past four decades, membrane development has occurred based on the demand in pressure driven processes. However, in the last decade, the interest in osmotically driven processes, such as forward osmosis (FO) and pressure retarded osmosis (PRO), has increased. The preparation of customized membranes is essential for the development of these technologies. Recently, several very promising membrane preparation methods for FO/PRO applications have emerged. Preparation of thin film composite (TFC) membranes with a customized polysulfone (PSf) support, electorspun support, TFC membranes on hydrophilic support and hollow fiber membranes have been reported for FO/PRO applications. These novel methods allow the use of other materials than the traditional asymmetric cellulose acetate (CA) membranes and TFC polyamide/polysulfone membranes. This review provides an outline of the membrane requirements for FO/PRO and the new methods and materials in membrane preparation.

Pleurotus ostreatus biofilm-forming ability and ultrastructure are significantly influenced by growth medium and support type

To investigate the effect of support and growth medium (GM) on Pleurotus ostreatus biofilm production, specific metabolic activity (SMA) and ultrastructure. Biofilms were developed on membranes covering a broad range of surface properties and, due to the applicative implications of mixed biofilms, on standard bacterial GM in stationary and shaken culture. Hydrophilic (glass fibre, Duran glass and hydroxyapatite) and mild hydrophobic (polyurethane, stainless steel, polycarbonate, nylon) supports were more adequate for biofilm attachment than the hydrophobic Teflon. Among the GM, sucrose-asparagine (SA) was more conducive to biofilm production than Luria-Bertani and M9. GM was more influential than support type on biofilm ultrastructure, and a high compactness was evident in biofilms developed on SA. Biofilms on Duran glass were more efficient than planktonic cultures in olive-mill wastewater treatment. The main effects of support and GM variables and their binary interactions on both biofilm production and SMA were all highly significant (P<0·001): thus, the magnitude of the effect of each variable strongly depended on the level of the other one. There is a lack of basic information regarding physiology and ultrastructure of P.ostreatus biofilms. To our knowledge, this is the first attempt to fill this gap, thus representing a basis for future studies.

Novel hydrophilic nylon 6,6 microfiltration membrane supported thin film composite membranes for engineered osmosis

Previous investigations of engineered osmosis (EO) concluded that hydrophobic support layers of thin film composite membrane causes severe internal concentration polarization due to incomplete wetting. Incomplete wetting reduces the effective porosity of the support, inhibiting mass transport and thus water flux. In this study, novel thin film composite membranes were developed which consist of a poly(piperazinamide) or polyamide selective layer formed by interfacial polymerization on top of a nylon 6,6 microfiltration membrane support. This intrinsically hydrophilic support was used to increase the “wetted porosity” and to mitigate internal concentration polarization. Reverse osmosis tests showed that the permselectivity of our best poly(piperazinamide) and polyamide thin film composite membranes approached those of a commercial nanofiltration and a commercial reverse osmosis membrane, respectively. The osmotic flux performance of the new polyamide thin film composite membrane showed matched water flux, 10 fold lower salt flux and 8–28 fold lower specific salt flux than the standard commercial cellulose triacetate forward osmosis membrane from Hydration Technology Innovations™. The relatively good performance in osmotic flux tests of our thin film composite membranes was directly related to the high permselectivity of the selective layers coupled with the hydrophilicity of the nylon 6,6 support. These results suggest that these nylon 6,6 supported thin film composite membranes may enable applications like forward osmosis or pressure retarded osmosis.

Numerical Analysis for Evaluating the Effect of Hydrophilic Anode Support for Water Management in Polymer Electrolyte Fuel Cells

Numerical Analysis for Evaluating the Effect of Hydrophilic Anode Support for Water Management in Polymer Electrolyte Fuel Cells

Vesicle deposition on hydrophilic solid surfaces

Supported lipid bilayers (SLBs) are popular as model systems for cell membranes and are promising for future applications in diagnostic devices and biomimetics. However, the mechanism of SLB formation is not fully understood. In this study, the deposition process of a single small unilamellar vesicle on hydrophilic supports is explored by dissipative particle dynamics. Depending on the lipid tail hydrophobicity and vesicle size, there exist three distinctive pathways of vesicle deposition, involving non-disintegrated, partially disintegrated, and completely disintegrated vesicle. A morphological phase diagram is presented and it reveals that a vesicle with weak tail hydrophobicity and small size tends to be completely disintegrated upon deposition. In contrast, the adsorption of an intact vesicle is observed as it possesses strong tail hydrophobicity and large size. Moreover, our simulation results clearly indicate that the deposition process of a vesicle onto the solid surfaces can be adjusted by altering the vesicular membrane tension and the interaction strength between the lipid head and the solid support. Finally, the deposition process of multiple vesicles on the hydrophilic solid surface is also investigated. The result shows that the fusion of vesicles has a tendency to hinder the formation of a SLB.

Principles and applications of steric exclusion chromatography

We introduce a chromatography method for purification of large proteins and viruses that works by capturing them at a non-reactive hydrophilic surface by their mutual steric exclusion of polyethylene glycol (PEG). No direct chemical interaction between the surface and the target species is required. We refer to the technique as steric exclusion chromatography. Hydroxyl-substituted polymethacrylate monoliths provide a hydrophilic surface and support convective mass transport that is unaffected by the viscosity of the PEG. Elution is achieved by reducing PEG concentration. Selectivity correlates with molecular size, with larger species retained more strongly than smaller species. Retention increases with PEG size and concentration. Salts weaken retention in proportion to their concentration and Hofmeister ranking. Retention is enhanced near the isoelectric point of the target species. Virus binding capacity was measured at 9.9×1012 plaque forming units per mL of monolith. 99.8% of host cell proteins and 93% of DNA were eliminated. Mass recovery exceeded 90%. IgM capacity was greater than 60mg/mL. 95% of host cell proteins were eliminated from IgM produced in protein-free media, and mass recovery was up to 90%. Bioactivity was fully conserved by both viruses and antibodies. Process time ranged from less than 30min to 2h depending on the product concentration in the feed stream.

Preparation of thin film composite membranes with polyamide film on hydrophilic supports

The interest in osmotically driven processes such as pressure retarded osmosis (PRO) has increased during the past decade. The synthesis of new membranes specifically designed for the process is essential for the development of these technologies. Conventional TFC have a relatively hydrophobic support layer e.g., polysulfone. However, a more hydrophilic support layer is desirable in osmotically driven processes as such supports would give better water flux, less internal concentration polarization (ICP) and less fouling. In the current project it was demonstrated that it is possible to coat a hydrophilic support membrane given there are enough functional/reactive groups on the surface of the support membrane. This is achieved by reacting the support with polyfunctional acid chlorides in a reaction step prior to interfacial polymerization (IP). In this way, covalent bonds between the support and the active layer are formed and the composite will be stabilized. Hydrolysed cellulose acetate CA membranes have been coated with a polyamide (PA) layer by this modified IP method. These membranes displayed a salt rejection up to 97%, and water fluxes from 7.6×10−7 to 4.7×10−6m3/m2/s at 1.3×106Pa differential pressures.

Electrochemical and PM-IRRAS studies of floating lipid bilayers assembled at the Au(111) electrode pre-modified with a hydrophilic monolayer

A floating bilayer lipid membrane (fBLM) assembled on a 1-thio-β-D-glucose (β-Tg)-modified Au(111) surface was engineered to mimic the environment of a biological cell membrane. This bilayer consists of a mixture of the phospholipid (DMPC), polyethylene glycol lipid (DMPE-PEG350) and cholesterol. Prior to membrane adsorption, a monolayer of β-Tg was first self-assembled at the Au(111) surface to increase the hydrophilicity of the electrode surface. The asymmetric bilayer was then deposited onto the hydrophilic support using a combination of Langmuir–Blodgett and Langmuir–Schaefer techniques. The inner leaflet of the bilayer was composed of DMPC, DMPE-PEG350 and cholesterol, while the outer leaflet consisted of DMPC and cholesterol. The hydrophilic PEG spacer subunit of the DMPE-PEG350 molecule promotes the formation of a water-rich domain, which separates the bilayer from the β-Tg modified surface. The Langmuir compression isotherms were recorded to examine the miscibility of these mixed monolayers at the air-solution interface of the Langmuir trough. Differential capacitance measurements showed that this fBLM was remained stable on the surface of the modified-gold electrode for potentials ranging from −0.40 to 0.45V versus Ag/AgCl and achieved a minimum capacitance of ∼3.0μFcm−2. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to obtain information regarding the conformation and orientation of the acyl chains and measure the degree of hydration of the phospholipid polar head groups within the film. These spectra demonstrated that the acyl chains of the lipids assume a small angle with respect to surface normal and that the phospho-glycerol groups are well-hydrated. The IR spectra of the PEG subunits demonstrated that the spacer unit adopts an amorphous, disordered conformation, which favors the hydration of the inner layer. This work demonstrates that the fBLM, composed of DMPE-PEG350 molecules, forms a water-rich region that separates the bilayer from the metal surface and that these new biomimetic systems are promising for future investigations involving transmembrane proteins.

Fabrication of thin film composite poly(amide)-carbon-nanotube supported membranes for enhanced performance in osmotically driven desalination systems

The search for lower energy consumption desalination systems has been driving research in the past decade towards the investigation of osmotically driven membrane processes, such as forward osmosis (FO) or osmotic distillation (OD). Despite similarities with reverse osmosis (RO) membranes, thin film composite (TFC) for FO membranes require careful design to reduce salt concentration polarization formation within the large pores composing the supporting layer. An investigation of a novel, highly stable, robust support made solely of carbon nanotubes (CNTs), which could find applications in both RO and FO was undertaken. TFC membranes were fabricated by interfacially polymerizing for the first time a dense poly(amide) (PA) layer on self-supporting bucky-papers (BPs) made of hydroxyl-functionalized entangled CNTs. These hydrophilic supports exhibited low contact angle with water (<20°), high water uptake capacity (17wt%), large porosity (>90%), making it a promising material when compared with poly(sulfone) (PSf), the traditional polymer used to fabricate TFC membrane supports in RO. In addition, the impact of the support hydrophilicity on the stability of the interfacially polymerized film and on water adsorption was investigated by oxygen-plasma treating various potential support materials, exhibiting similar geometrical properties. The morphology and salt diffusion of both CNT BP and PSf supports were investigated, and the novel BP–PA composite membranes were found to be superior to commercially available TFC membranes.

Synthesis of novel polymer poly(glycidyl methacrylate) incorporated with tetranitrofluorenone for selective removal of neutral nitrogen species from bitumen-derived heavy gas oil

Over the last two decades, numerous studies have been undertaken in identifying the inhibiting and deactivating effects of basic nitrogen compounds present in heavy gas oil (HGO) on catalyst active sites; however, limited information is available on the presence and effect of neutral nitrogen species, which have shown to exhibit both inhibitory and deactivating effects comparable to those of the basic species. A novel pretreatment process employing the heterogeneously cross-linked macroporous polymer poly(glycidyl methacrylate) as the hydrophilic support coupled with organic compound tetranitrofluorenone has been synthesized in a four stage procedure for the selective removal of neutral nitrogen heterocyclic compounds from heavy gas oil using charge transfer complexes. Scanning electron microscopy (SEM), low temperature N2 adsorption–desorption (BET), CHNOS elemental analysis, Fourier transform infrared spectroscopy (FT-IR), epoxy content titration, and thermo gravimetry/differential thermal analyzer (TG/DTA) were employed for determining the optimum parameters during the synthesis of each stage. The optimized polymer has shown promising results with successful removal of up to 6.7% of the nitrogen species in a single contact using approximately 15wt.% of the polymer with respect to HGO, while having little to no influence on the sulfur species. The reusability of the polymer has also shown consistency in the selective removal of nitrogen compounds, with continuous removal rates in the range of 6.7%.

Synthesis of TiO2/SBA-15 photocatalyst for the azo dye decolorization through the polyol method

The nano-sized TiO2 powder and immobilized TiO2/SBA-15 photocatalysts were synthesized via a polyol method with an attempt to increase the quantitative effect by reducing the particle size and avoid the aggregation by immobilizing on hydrophilic SBA-15 support. The effect of reduction temperature on the TiO2 crystalline size was investigated. The X-ray diffraction (XRD) and Field-emission scanning electron microscopy (FE-SEM) results showed that the crystallite size of the TiO2 particles is in the nano-regime and indicated that depended on the nucleation and growth process, different sizes and shapes of monodisperse or polydisperse TiO2 powders are formed. The photocatalytic activities of the samples were evaluated for the decolorization of an ano dye, acid red 1 (AR1) were studied in aqueous solution under UV light irradiation. The effect of different parameters such as catalyst dosage, solution pH, TiO2 loading weight, and different support materials Al2O3 and glass bead on the decolorization efficiency of AR1 were studied. The results indicated that the self-synthesized TiO2 showed comparable decolorization efficiency than commercial P25, and the efficiency can be significantly improved by using SBA-15 as support material due to its hydrophilicity.

Thin-film composite forward osmosis membranes with novel hydrophilic supports for desalination

In this work, a novel sulphonated poly(ether ketone) (SPEK) polymer with super-hydrophilic nature was designed as the substrate material to fabricate high performance thin-film composite (TFC) membranes for desalination via forward osmosis (FO). m-Phenylenediamine (MPD) and 1,3,5-trimesoylchloride (TMC) were employed as the monomers for the interfacial polymerization reaction to form a thin aromatic polyamide selective layer. It has been demonstrated that blending a certain SPEK material into the polysulfone (PSU) substrate of TFC-FO membranes not only plays the key role to form a fully sponge-like structure, but also enhances membrane hydrophilicity and reduces structure parameter. The TFC-FO membrane comprising 50wt% SPEK in the substrate shows the highest water flux of 50 LMH against deionized water and 22 LMH against the 3.5wt% NaCl model solution, respectively, when using 2M NaCl as the draw solution tested under the pressure retarded osmosis (PRO) mode (draw solution flows against the selective layer). It is found that the hydrophilicity and thickness of the substrates for TFC-FO membranes play much stronger roles in facilitating high water flux in FO for desalination compared to those made from hydrophobic substrates full of finger-like structures. Moreover, the reduced membrane structural parameter indicates that the internal concentration polarization (ICP) can be remarkably reduced via blending a hydrophilic material into the membrane substrates. Thermal treatment of TFC-FO membranes with optimized conditions can also improve the membrane performance and mechanical strength.