Gelation Medium Research Articles

Polyacrylonitrile (PAN)/IGEPAL blend asymmetric membranes: preparation, morphology, and performance

Polyacrylonitrile (PAN) membranes are widely applied in many chemical engineering fields. In this research, novel asymmetric PAN membranes with high hydrophilicity and permeability were prepared from a PAN/polyoxyethylene (40) nonylphenyl ether (IGEPAL)/NMP system via immersion precipitation. Pure water was used as the gelation medium. The effects of adding IGEPAL, the coagulation bath temperature (CBT), and the PAN concentration on the morphology, wettability, and permeability of the prepared membranes were studied by scanning electron microscopy (SEM), contact angle measurement, and permeation experiments. The results demonstrated that both the hydrophilicity and the permeability of the prepared membranes were significantly enhanced by the addition of IGEPAL surfactant to the casting solution. Also, it was found that decreasing the PAN concentration and increasing CBT resulted in the formation of membranes with high permeability and sublayer porosity.

Polysulfone/Brij‐58 blend nanofiltration membranes: preparation, morphology and performance

In present research, novel asymmetric polysulfone (PSF) membranes with high hydrophilicity and noticeable rejection of arsenic, as one of the major environmental problems, were prepared from PSF/Brij‐58/NMP (1‐methyl‐2‐pyrrolidone) system via immersion precipitation. Pure water was used as gelation media. The variation effect of coagulation bath temperature (CBT) and addition of Brij‐58 on morphology, wettabiliy, pure water permeation flux and rejection of As (III) and As (V), as two dominant states of arsenic in the nature, were studied by scanning electron microscopy, contact angle measuring instrument and experimental setup. The results demonstrated that both hydrophilicity and rejection properties of the prepared membranes were significantly enhanced by small addition of Brij‐58 surfactant in the casting solution along with using the lowest level of CBT. Addition of 4 wt. % of Brij‐58 and using cold coagulation bath resulted in the highest rejection of As (V). Initial increase in Brij‐58 concentration, from 0 wt. % to 2 wt. %, resulted in higher rejection of As (III). However, higher Brij‐58 concentrations than 2 wt. % (increase from 2 wt. % to 6 wt. %) led to lower rejection of As (III). Also, it was found out that addition of Brij‐58 in the casting solution along with increasing the CBT resulted in formation of membranes with high permeability and sub‐layer porosity and thin top layer. Copyright © 2012 John Wiley & Sons, Ltd.

Preparation of modified polyethersulfone membranes using variation in coagulation bath temperature and addition of hydrophilic surfactant

In this study, novel asymmetric polyethersulfone membranes were prepared from PES/PEG/Tween-20/NMP system via immersion precipitation. Pure water was used as gelation media. Simultaneous effects of variation in coagulation bath temperature (CBT) and addition of Tween-20 on morphology, wettabiliy, pure water permeation flux (PWF) and bovine serum albumin (BSA) rejection of the prepared membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measuring instrument and experimental set up. The obtained results indicate that the small addition of surfactants in the casting solution along with using the lowest level of CBT increases hydrophilicity of the PES membranes. Also it was found out that addition of Tween-20 in the casting solution along with increasing the CBT incites the formation of the bigger pores on the top surface and results in the formation of membranes with higher porosity in the sublayer.

Preparation and characterization of nanoporous polysulfone membranes with high hydrophilic property using variation in CBT and addition of tetronic‐1107 surfactant

AbstractAsymmetric polysulfone (PSF) membranes were prepared from PSF, Tetronic‐1107, and 1‐methyl‐2‐pyrrolidone (NMP) via immersion precipitation. Pure water was used as the gelation media. The effects of coagulation bath temperature (CBT) (0 and 25°C), and addition of Tetronic‐1107 on the morphology, wettability, and pure water permeation flux (PWF) of the prepared membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurements, and experimental set up. The contact angle measurements demonstrated that the hydrophilicities of the nanoporous PSF membranes were significantly enhanced by addition of a small amount of Tetronic‐1107 surfactant in the casting solution, along with using the lower CBT. It was also found that addition of Tetronic‐1107 in the casting solution along with increasing the CBT from 0 to 25°C incites formation of bigger pores on the top surface and results in formation of membranes with higher thickness and more porous structure in the sublayer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and characterization of modified polysulfone membranes with high hydrophilic property using variation in coagulation bath temperature and addition of surfactant

AbstractIn this research, novel asymmetric polysulfone (PSF) membranes were prepared from PSF/polyethylene glycol (PEG)/polyoxyethylene sorbitan monolaurate/1‐methyl‐2‐pyrrolidone (NMP) system via immersion precipitation. Pure water was used as gelation media. The variation effect of coagulation bath temperature (CBT) and addition of surfactant on morphology, wettability, and pure water flux (PWF) of the prepared membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measuring instrument, and experimental set up. The contact angle measurements demonstrated that hydrophilicity of the PSF membranes was significantly enhanced by small addition of surfactant in the casting solution along with using the lowest level of CBT. Also it was found out that addition of the surfactant in the casting solution along with increasing the CBT incites the formation of the bigger pores on the top surface and results in the formation of membranes with higher thickness and more porous structure in the sublayer. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Chitosan oligosaccharide as prospective cross-linking agent for naproxen-loaded Ca-alginate microparticles with improved pH sensitivity

Objectives: The aim of the presented work was to develop Ca-alginate microparticles for oral administration of naproxen reinforced with chitosan oligosaccharide (COS) with a special interest to examine the potential of COS for improvement of microparticles stability in simulated intestinal fluid (SIF).Method: Microparticles were prepared according to the two-step procedure using an air-jet device with varying calcium chloride and COS concentration in the gelling medium. All prepared microparticles were subjected to size determination, morphology, surface, and inner structure analysis by scanning electron microscopy (SEM), drug loading (DL) and encapsulation efficiency (EE), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, in vitro swelling, and drug release studies.Results: In general, COS-treated microparticles were spherical in shape but somewhat deformed, exhibiting the surface roughness with the mean particle size less than 350 µm. FT-IR and DSC studies confirmed the formation of polyelectrolyte complex (PEC) between alginate and COS, whereas chemical properties and crystalline state of naproxen were unaffected by the encapsulation process. Low naproxen solubility in the gelling medium and rapid entrapment resulted in high encapsulation efficiency (>80.0%). The results of swelling studies demonstrated that COS-treated particles were less sensitive to swelling and erosion in SIF in comparison to the nontreated particles. This resulted in prolonged drug release in SIF, which was dependent on the COS/alginate ratio.Conclusion: The obtained findings proved that COS could be used as an effective cross-linking agent for improvement of Ca-alginate microparticles stability in SIF, allowing prolonged release of the encapsulated drug after oral administration.

Development of High Performance Nanofiltration Membranes with Hydrophilic Surface for the Removal of Cadmium from Contaminated Water

In present research, novel asymmetric polysulfone (PSF) membranes with high hydrophilicity and noticeable rejection of cadmium, as one of the major environmental problems, were prepared from PSF/PEG400/NMP system via immersion precipitation. Pure water was used as gelation media. The variation effect of the coagulation bath temperature (CBT) and addition of PEG400 on morphology, wettability, and permeability of the prepared membranes were studied by scanning electron microscopy (SEM), contact angle measuring, and the experimental set up. The results demonstrated that both the hydrophilicity and the rejection properties of the prepared membranes were significantly enhanced by a small addition of PEG400 in the casting solution along with using the lowest level of CBT. Also, it was found out that the addition of PEG400 in the casting solution along with increasing the CBT resulted in the formation of membranes with high permeability and sub-layer porosity and thin top layer.

Study of the optimization factors for preparation of heterogeneous reverse osmosis membranes

The influence of the preparation factors such as casting solution composition, different methods of coal modification, evaporation time of solvent and their optimization on performance of cellulose acetate heterogeneous reverse osmosis membranes have been studied. Three types of membranes were made from a blend of cellulose acetate (CA) and coal by weight ratios 1:1.5, 1:1.75 and 1:2. The powdered coal was modified with nitric acid and aryl diazonium salts in acetonitrile medium at constant modification time. The membranes were prepared by phase inversion process from a casting solution of cellulose acetate-coal and magnesium perchlorate in acetone water mixture at varying evaporation time of solvent at constant temperature using the same gelation medium. The composition of raw and modified coals was examined by IR spectroscopy. Membranes obtained with a casting solution composition of cellulose acetate-coal in weight ratios of 1:1.5 and 1:1.75, modified coals and longer evaporation time of solvent showed the best performance.

Poloxamer Thermogel Systems as Medium for Crystallization

To prepare a thermoreversible gel system able to work as a medium for crystallization at around 20°C, allowing easy retrieval of crystals by simply decreasing the gel temperature. Lactose was selected has model substance for crystallization. Water solutions with different% of poloxamer 407, α-Lactose monohydrate, and ethanol were prepared and analysed by rheology to understand how the different components alter the gelling temperature. The systems with the required characteristics for lactose crystallization were prepared and the crystals recovered by cooling and then filtering the dispersion. Rheological analysis showed interaction between the poloxamer and lactose. Increasing the quantity of poloxamer or lactose lowered the gelation temperature while the addition of small amounts of ethanol had a modest effect on the same property. These data were used to identify the ideal concentration of the components in order to prepare a system matching the features of our purpose. Such system yielded high quality crystals, with well-defined geometry and narrow particle size distribution. Poloxamer is a very interesting polymer in that it is able to generate a reversible gelling medium from which crystals can be harvested by filtering, without the addition of any chemicals to promote the sol-gel transition.

Study on the Dynamic Rheometry and Swelling Properties of the Polyacrylamide/Laponite Nanocomposite Hydrogels in Electrolyte Media

Polyacrylamide/laponite/chromium triacetate nanocomposite (NC) hydrogels were prepared by incorporation of the laponite nanoparticles in partially hydrolyzed polyacrylamide followed by cross-linking of their aqueous solutions with chromium triacetate. Influence of nanoparticle, cross-linker, polymer concentrations, and gelation media (water) temperature, salinity, and rheometer frequency on the viscoelastic behavior of the NC hydrogels were studied by probing the network properties. In addition, swelling behaviors of these NC gels in tap and oil reservoir water were evaluated. According to dynamic rheometry of the gelation process, the limiting storage modulus of the NC gels increased with increasing laponite content. The addition of laponite into the polyacrylamide gelling system increased their viscous properties more strongly than the elastic properties. The ultimate elastic modulus of the NC gels increased with increasing water salinity and temperature. Increasing rheometer frequency during gelation retarded the sol–gel transition and decreased the ultimate elastic modulus. The equilibrium swelling ratio of the NC hydrogels in tap water decreased with increasing laponite content. The salt sensitivity of the NC gels in oil reservoir water slightly decreased with increasing laponite content. These results suggest the superiority of the hydrolyzed polyacrylamide (HPAM)/chromium acetate/laponite NC hydrogels for water shut-off applications in oil reservoirs as compared with unfilled HPAM gels.

A novel dual-structure, self-healable, polysaccharide based hybrid nanogel for biomedical uses

A new unique dual-structure hydrogel composed of nanostructures of amphiphilic chitosan (CHC) dispersed in a sodium alginate matrix (SAL) is presented. The successful creation of the composite is based on combining chitosan and sodium alginate without precipitation or agglomeration, which has not been previously reported. The CHC/SAL composite gels present a number of properties making them attractive for biomedical applications, in particular as implantable depot gels or in dermal applications. The gels are shown to form rapidly upon exposure of the combination solution to Ca2+ containing gelation medium. The formed gels have storage moduli similar to soft tissue and display shear reversible gelation with fast recovery of mechanical properties, in addition to self-healing capability at certain compositions. The gels exhibit moderate swelling in deionized water and low swelling in simulated body fluid and cell culture media. The drug release from the composite gels is demonstrated using the hydrophobic drug all-transretinoic acid, which is used in cancer and skin disorder therapies. The drug release initially occurs through a Fickian mechanism for a fraction of the loaded drug, where the fraction released during this process depends on release media and gel composition. A large fraction of the loaded drug can be retained for long term depot drug delivery. Furthermore, the CHC/SAL gels are determined to have low toxicity and skin irritation.

Nano-porous polyethersulfone (PES) membranes modified by acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) as additives in the gelation media

In this study, the effects of addition of acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) in the gelation media on structure and permeation properties of polyethersulfone (PES) membranes were investigated. The membranes were prepared by phase inversion method using PES and polyvinylpyrrolidone (PVP) in dimethylacetamide (DMAC) as solvent. The surface and sub-layer morphologies of the obtained membranes were analyzed by scanning electron microscope (SEM) and atomic force microscope (AFM). The membrane performance was evaluated in terms of pure water permeation, non-skim milk water permeation, milk protein rejection, fouling analysis and solute separation of polyethylene glycol (PEG) solution of various molecular weights. The morphological studies showed that the average pore sizes of the surface and sub-layer were reduced at the presence of AA and HEMA in the gelation media. Meanwhile, the surface porosity was increased. The mean pore size ranged from 5.2 to 11.3 nm when calculated from the solute transport data. The pure water flux, milk water permeation and protein rejection of the membranes were improved by increasing the AA and HEMA contents in the gelation media. The fouling analysis indicated that the membrane resistance against filtration was decreased. In conclusion the antifouling properties of PES membranes were improved by addition of AA and HEMA in the gelation media.

Improvement of performance and surface properties of nano-porous polyethersulfone (PES) membrane using hydrophilic monomers as additives in the casting solution

The effects of hydrophilic monomers e.g. acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) on the morphology and performance of polyethersulfone (PES) membrane were investigated. The membranes were fabricated from a casting solution of PES, dimethylacetamide (DMAC), polyvinylpyrrolidone (PVP) and AA or HEMA via phase inversion induced by immersion precipitation. The mixture of water (80 vol.%) and 2-propanole (IPA, 20 vol.%) was employed as gelation media. The prepared membranes were characterized using ATR-FTIR, SEM, AFM, contact angle, viscosity measurements, ultrafiltration performance and fouling analysis. The hydrophilicity of PES membrane was improved after addition of AA and HEMA in the casting solution. The morphological studies (SEM and AFM) showed that the average sizes of membrane pores in surface and sub-layer were reduced with addition of AA and HEMA in the casting solution. Meanwhile the surface porosity was increased. The surface pore size of the untreated PES membrane was decreased from 138 nm to 45.1 and 40.6 nm with introducing 15 wt.% AA and HEMA, respectively. The experimental results showed that the pure water fluxes of membranes were declined at the presence of AA and HEMA. Moreover, the milk water permeation and protein rejection were improved at these conditions. Finally, the fouling analysis demonstrated that the membranes show fewer tendencies for fouling.

Preparation and surface modification of hollow fibre membranes for drinking water disinfection and water reclamation

Polysulphone hollow fibres were spun according to phase inversion process under different conditions by extrusion of dimethylformamide solution of the polymer through double orifice spinneret using water or water-DMF mixture as gelation medium. The membrane surface was modified by in situ interfacial polymerisation of m-phenylenediamine with trimesoyl chloride. The nominal molecular weight cut-off (MWCO) values of the virgin fibres were 44,000?94,000 g/mol, which were decreased to 10,000?14,000 g/mol upon surface modification. The contact angle of the virgin fibres was about 87° and was decreased to about 65° by surface modification. HF modules exhibited pure water fluxes of 40?70 litre/m²h at 25 psi, and 4?5 log reduction for microorganisms like cocci, E. coli and bacillus when tested with water containing 1010 cfu/ml of bacteria. Fibres were tested for the treatment of municipal sewage water for a period of 20 days and constant rejection-flux profile was observed throughout the period.

Alginate-Chitosan Particulate System for Sustained Release of Nimodipine

Purpose: The aim of this work was to prepare nimodipine-loaded alginate-chitosan beads for sustained drug release.Methods: Nimodipine-loaded alginate-chitosan beads were prepared by ionic gelation method using various combinations of chitosan and Ca2+ as cations and alginate as anion. The swelling ability and invitro drug release characteristics of the beads were studied at pH 1.2 and 6.8. Infra-red (IR) spectrometry, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), x-ray diffraction (XRD), and atomic absorption spectroscopy (AAS) were also applied to investigate thephysicochemical characteristics of the drug in bead formulations.Results: The surface morphology, size, and drug loading of the beads varied with increase in the concentration of chitosan and calcium chloride in the gelation medium. The swelling ability of the beadsin different pH media was dependent on the presence of a polyelectrolyte complex in the beads and the pH of the media. Both calcium alginate beads and the beads treated with chitosan failed to release thedrug at pH 1.2 over the period of study. On the other hand, at pH 6.8, calcium alginate beads released approx. 96 % of drug in 6 h, but treatment of the beads with chitosan lowered drug release to 73 %.Drug release mechanism was either “anomalous transport” or “case-II transport”. Data from characterisation studies indicate that there was no significant change in the physical state of the drug inthe bead formulations

Adipic acid dihydrazide treated partially oxidized alginate beads for sustained oral delivery of flurbiprofen

In this study, periodate oxidation of sodium alginate was controlled such that the oxidized alginate could form isolatable beads with Ca+2 ions. The beads of oxidized alginate having a degree of oxidation 1 mol%, entrapped 89% flurbiprofen and released almost all of its content within 1.5 h in pH 7.2 phosphate buffer solution. The beads were covalently crosslinked with adipic dihydrazide (ADH) in addition to ionic crosslinks and were characterized. Scanning electron microscopy revealed that the beads were spherical having smooth surfaces. The drug entrapment efficiency decreased (90–86%) with increasing concentration of ADH (2–6% w/v) in the gelation medium. However, the beads prolonged the drug release in alkaline dissolution medium up to 8 h depending upon the concentration of ADH. The beads prepared with 2% ADH swelled more rapidly and led to faster drug release in either pH 1.2 HCl solution or pH 7.2 phosphate buffer solution. The swelling tendencies were reduced and the drug release became slower with higher concentrations in either fluid. The drug diffusion from the beads followed super case II transport mechanism. FTIR spectroscopy indicated stable nature of flurbiprofen in the beads and therefore had potential as sustained oral delivery system for the drug.

Porometry Studies of the Polysulfone Membranes on Addition of Poly(ethylene Glycol) in Gelation Bath During Preparation

Polysulfone membranes are prepared through phase separa- tion technique, introduced by Loeb-Sourirajan. The viscous polymer solution (in dimethyl formamide) is first spread into the thin film, and then immersed in gelation medium (water). The influence of poly- meric additive, (poly(ethylene glycol) (PEG)) in the formation of the pores during phase separation in gelation bath (i.e. from the polymer poor phase, which appears at the phase separation) is explored. The effects of different molecular weight (Mw) of PEG in the gelation bath regarding the differential filter flows of nitrogen as well as their concentration are reflected from the porometry studies. The pore dis- tribution is shifted as the molecular weight of PEG used in the gela- tion bath. The bubble point and mean flow pore diameters vary with the concentration as well as their molecular weight of PEG.

Development and evaluation of new sustained-release floating microspheres

A type of multi-unit floating alginate (Alg) microspheres was prepared by the ionotropic gelation method with calcium carbonate (CaCO 3) being used as gas-forming agent. Attempts were made to enhance the drug encapsulation efficiency and delay the drug release by adding chitosan (Cs) into the gelation medium and by coating with Eudragit, respectively. The gastrointestinal transit of optimized floating sustained-release microspheres was compared with that of the non-floating system manufactured from identical material using the technique of gamma-scintigraphy in healthy human volunteers. It was found that the drug encapsulation efficiency of Cs–Alg microspheres was much higher than that of the Ca–Alg microspheres, and coating the microspheres with Eudragit RS could extend the drug release significantly. Both uncoating and coating microspheres were able to continuously float over the simulated gastric fluid (SGF) for 24 h in vitro. Prolonged gastricretention time (GRT) of over 5 h was achieved in the volunteer for the optimized coating floating microspheres (FM). In contrast, non-floating system (NFM) could be emptied within 2.5 h. In the present study, a multi-unit system with excellent floating ability, optimum drug entrapment efficiency and suitable drug release pattern has been developed.

Studies in the Development of Nateglinide Loaded Calcium Alginate and Chitosan Coated Calcium Alginate Beads

Nateglinide loaded alginate-chitosan beads were prepared by ionic gelation method for controlling the drug release by using various combinations of chitosan and Ca2+ as cation and alginate as anion. IR spectrometry, scanning electron microscopy, differential scanning calorimetry and X-ray powder diffractometry were used to investigate the physicochemical characteristics of the drug in the bead formulations. The calcium content in beads was determined by atomic absorption spectroscopy. The swelling ability of the beads in different media (pH 1.2, 4.5, 6.8) has been found to be dependent on the presence of polyelectrolyte complex of the beads and the pH of the media. The ability to release the Nateglinide was examined as a function of chitosan and calcium chloride content in the gelation medium. It is evident that the rate of drug release and its kinetics could be controlled by changing the chitosan and the calcium chloride concentrations. Calcium alginate beads released more than 95% of drug with in 8 h; whereas coated beads sustained the drug release and released only 75-80% of drug. The drug release mechanism analyzed indicates that the release follows either "anomalous transport" or "case-II transport".

The effect of anionic, non-ionic and cationic surfactants on morphology and performance of polyethersulfone ultrafiltration membranes for milk concentration

In this study, the effects of three surfactants, sodium dodecyl sulphate (SDS) as anionic surfactant, cetyle three methyl ammonium bromide (CTAB) as cationic surfactant and Triton X-100 as non-ionic surfactant on structure and performance of polyethersulfone membranes prepared from PES/PVP/DMAC system via immersion precipitation have been investigated. The mixture of water and isopropyl alcohol (IPA) (30/70 vol.%) was used as gelation media. The morphology and performance of the prepared membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and separation experiments using pure water and milk as feed. The obtained results indicate that the small addition of surfactants in the casting solution increases the porosity of the membrane support layer, enhances pure water flux and milk water permeation.