Aqueous Solution Of Sodium Alginate Research Articles

Submicron aerosols of liquid fuels: Method of production, experimental characterization and a semi-empirical model

For combustion processes involving the atomization of liquid fuels, the minimization of droplet size is important for enhancing fuel vaporization, increasing the efficiency of air-fuel mixtures, and reducing soot and NOx emissions. In this paper, a methodology for producing aerosols of submicron-sized droplets for liquid fuels is presented. The method of droplet formation is based on disintegration, by gas jets, of thin liquid films formed as bubbles on a liquid surface. Using compressed air and CO2, we atomized and studied droplet aerosols of gasoline, diesel, and 0.1–2 wt% aqueous solutions of sodium alginate, with dynamic viscosities up to 210 mPa s, as models of a highly viscous alternative fuel. The produced droplet volume distributions were bi-modal with two peaks between the droplet diameters 0.1–1 µm and 1–10 µm; the respective volume and Sauter mean droplet diameters were substantially smaller than typically produced by other atomization methods, reaching minima between 0.4 and 0.7 μm. The liquid flow rates of a few hundreds of mg/min for 2 wt% sodium alginate solution and ∼20 g/min for gasoline were measured. The minima of the observed air-to-liquid mass ratios were smaller than the respective stoichiometric air-fuel ratios. Dimensional analysis allowed identifying a dimensionless parameter not previously described in the literature, which plays a primary role in the aerosol production process. This analysis and the experimental data enabled establishment of a semi-empirical model describing the droplet aerosol production by the liquid atomization method used here. The potential advantages demonstrated in this study over the existing fuel atomization techniques include the small size of the generated droplets, simplicity of the method and the device design, low-cost of manufacturing, easy operation and scale-up. Submicron fuel droplets are expected to decrease environmental impact in combustion applications, which suggests further investigations and development of the presented fuel atomization technique.

Characterization and quantification of structure and flow in multichannel polymer membranes by MRI

Polymeric multichannel hollow fiber membranes were developed to reduce fiber breakage and to increase the volume-to-membrane-surface ratio and consequently the efficiency of filtration processes. These membranes are commonly used in ultrafiltration and are operated in in-out dead-end mode. However, some of the filtration details are unknown. The filtration efficiency and flow in the multichannel membranes depend on filtration time and are expected to vary along spatial coordinates. In the current work, in-situ magnetic resonance imaging was used to answer these questions. Velocities were quantified in the feed channels to obtain a detailed understanding of the filtration process. Flow and deposits were measured in each of the seven channels during filtration of sodium alginate, which is a model substance for extracellular polymeric substances occurring in water treatment. Volume flow and flow profiles were calculated from phase contrast flow images. The flow in z-direction in the center channel was higher than in the surrounding channels. Flow profiles variate depending on the concentration of Ca2+, which changes the filtration mechanism of aqueous solutions of sodium alginate from concentration polarization to gel layer filtration.

Hybrid gels: Influence of oleogel/hydrogel ratio on rheological and textural properties

Hybrid gels can be used for controlled delivery of bioactives and for textural and rheological modification of foods. In this regard the hydrogel:oleogel ratio and gel development methodologies showed to be the aspects that influence most of their properties. The present study shows how different fractions of oleogel can influence the hydrogel matrix of an oleogel-in-hydrogel emulsified system in terms of polymorphic arrangement, microstructure, texture and rheology. The hydrogel was prepared by using an aqueous sodium alginate solution and the oleogel was prepared through the gelation of medium chain triglycerides with beeswax. Hybrid gels were prepared under constant shearing. Crystallinity was clearly changed as hydrogel and oleogel were combined. No polymorphism was observed in the X-Ray diffraction of hybrid gels, as these showed homogeneous results for all component ratios. The behaviour of samples with increasing oleogel-to-hydrogel ratio presented a decrease of both firmness and spreadability, and then, a decrease of gel adhesivity and cohesiveness. This textural response was a consequence of the disaggregated structure, stemming from the disruption of the hydrogel network, due to the inclusion of increasing amounts of oleogel. Rheological results showed that all hybrid gels presented a gel-like behaviour (G´ > G´´). Oleogel's strength influenced the overall textural and rheological performance of hybrid gels. This work demonstrates the possibility of producing hybrid gels aiming to tailor texture on food systems.

Effect of cabergoline alginate nanocomposite on the transgenic Drosophila melanogaster model of Parkinson’s disease

Parkinson’s disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra of the midbrain. Dopamine agonists help the patients with PD by reversing the dopamine depletion and related motor deficits. In the present work, cabergoline, a potent ergot dopamine agonist, was given in the form of cabergoline alginate nanocomposite (CANC) to the PD model flies to study its effects on climbing ability, activity pattern, life span, lipid peroxidation, glutathione (GSH) content, glutathione-S-transferase (GST) activity, dopamine content, protein carbonyl content, mean gray-scale values, and caspase-3 and caspase-9 activities. Cabergoline alginate nanocomposite was synthesized by adding the cabergoline solution in the warm aqueous solution of sodium alginate; The synthesized CANC was characterized using fourier transform (FTIR) infrared spectroscopy, transmission electron microscopy (TEM), and UV–Visible spectroscopic techniques. The synthesized CANC having the final doses of 1, 2, and 3 μM was supplemented with diet and the flies were allowed to feed on it for 24 days. Cabergoline alginate nanocomposite significantly increases climbing ability, reduces lipid peroxidation, GST activity, protein carbonyl content, caspase 3/9 activity, mean gray-scale values, and increases the GSH as well as dopamine content in a dose-dependent manner. The results of this study suggest that CANC is potent in delaying and reducing the symptoms of PD.

Alginate/soy protein system for essential oil encapsulation with intestinal delivery

Preparation of alginate-soy protein isolate (AL/SPI) complex beads containing essential oil of thyme was carried out by emulsification of thyme oil in aqueous sodium alginate solution blended with SPI solution, followed by atomization via electrostatic extrusion and gelification with calcium ions. The process parameters were optimized by variation of the alginate (1–2.5 wt.%) and SPI (0–1.5 wt.%) concentrations. Dry alginate-SPI particles exhibited wrinkle surface while shape distortion of hydrogel beads occurred with ≥1.5 wt.% alginate concentration, whereas SPI induced reduction of the particle size. Encapsulation efficiency of 72–80 % based on total polyphenols was achieved. In SGF the samples exhibited oil release of 42–55 % (due to matrix shrinkage and proteins degradation by pepsin activity), while the rest was delivered in SIF within 2.5 h simultaneously with swelling and degradation of the matrix.

(Invited) Shear-Induced Fabrication of Multiple Parallel Gel Filaments Using Aqueous Two-Phase Separation

Macroscopic structures of gel fibers have been prepared by control of the polymer solution properties and by design of the nozzle and flow path of the microfluidic device. In this research, we investigated a method to simultaneously fabricate hundreds to thousands of gel filaments simply by flowing the polymer solution inside the capillary without spinneret. An aqueous two-phase separation (ATPS) can be induced by adjusting their concentration in certain combinations of two polymers. The respective polymer concentration in each phase can be determined from the phase diagram, whereas an assembly of heterogeneous polymers generate in each phase. Hydrodynamic properties of pre-gel solution can be controlled by inducing such heterogeneous polymer assemblies. A co-axial flow double capillary was used to fabricate gel filaments, where an inner capillary (inner diameter 0.7 mm) was fixed at the insert position of an outer capillary. To induce ATPS, an ionic strength for the aqueous solution of sodium alginate (Alg) / polyethylene glycol (PEG) mixture was controlled by NaCl addition. The pre-gel Alg/PEG solution was flown as an inner flow of glass double capillaries, where a crosslinker solution (Ca2+ soln.) was flown as a sheath flow. The obtained gel was composed of multiple parallel gel filaments with a diameter of several micrometers, while a single gel without filament structure was obtained from the homogeneous solution without NaCl addition. In aqueous solution, the Alg chain has a structure with few entanglements because of its rigidity. The rigid assembly of alginate is mainly caused by guluronic acid block, that is stabilized by diaxial linkages via intramolecular hydrogen bonds. The shear stress generated by flowing the aqueous Alg solution inside the capillary cannot induce deformation of its rigid assembly, results in the single thick gel filament. By complexation with PEG, destruction of regular hydrogen bond was responsible for breaking the rigid structure of Alg. Thus, deformation of Alg/PEG assembly was enabled to elongate as the fibrous structure by the shear stress, followed by gelation in contact with Ca2+ ions at the outlet of the inner capillary. Such shear-induced deformation of the Alg/PEG assembly was studied by measuring viscoelastic properties with a spindle viscometer. Besides, Alg/PEG assembly generation in each phase was determined by size-exclusion chromatography with a multi angle light scattering detector. This presentation will discuss a simple technique for preparing multiple gel filaments simply by passing a polymer solution through a capillary.

Preparation of Multiple Parallel Protein-polysaccharide Hybrid Gel Filaments Under Shear

Fabrication of anisotropic gel with characteristic structures has been reported using a flow system with three dimensional microfluidic devices. Such gel structures are mainly achieved by design and preparation of the microchannel for flowing pre-gel solution. In this research, we propose a method for preparing multiple parallel gel filaments by controlling viscoelastic properties of polymer assembly as the fluid of microfluidic devices. To promote the formation of heterogeneous assembly of different types of macromolecules, an aqueous two-phase separation (ATPS) technique was utilized. Two layers of aqueous solutions appear when the ATPS conditions including ionic strength, temperature, and solute concentration in certain combinations of two components are satisfied. In respective phase, some solute molecules form heterogeneous assemblies because the solutes in respective phase are highly concentrated. We previously reported that the alginate (Alg) could form the assembly with polyethylene glycol (PEG) in the induced phase of Alg/PEG/NaCl system. In aqueous media, the Alg assembly has the rigid structure because diaxial linkages in a successive region of guluronic acid are stabilized by hydrogen bonds. Destruction of hydrogen bonds of Alg molecules by interaction with PEG enables deformation of Alg assembly by shear. Gel filaments were prepared with a co-axial flow device as double glass tubes, where an inner tube (inner diameter 0.7 mm) was fixed at the insert position of the outer tube. Pre-gel solution and crosslinker solution respectively were flown to inner and outer tube using syringe pumps. The morphology of the gel filaments was observed by a scanning electron microscope. A single thick gel filament was obtained from aqueous sodium alginate solution, whereas multiple thin gel filaments were obtained when a mixed solution of Alg and PEG under the ATPS condition. Appearance of shear-thinning behavior for the Alg-rich phase suggests that the complexation of Alg with PEG was responsible for destruction of the rigid assembly due to breaking hydrogen bonds. In this poster, the method will be applied to the protein containing system to fabricate the protein-polysaccharide hybrid filaments.

Supramolecular complexation of the cationic derivative of Zn (II) phthalocyanine and sodium alginate in mixed aqueous solutions

The processes of supramolecular complexation in mixed dilute aqueous solutions of sodium alginate and positively charged Zn (II) phthalocyanine derivative were investigated by spectrophotometry and dynamic light scattering methods. The complexation is accompanied by fluorescence quenching. The process of complexation includes the stages of electrostatic self-assembly, intra-supramolecular rearrangement, metastable state and phase separation. The hydrodynamic radius and zeta potential of the complex in the metastable state for different compositions of mixed solutions are determined. The pH range of the existence of the complex and the conditions for its dissociation upon introduction of a low molecular weight electrolyte and a cationic polysaccharide are determined.

Functionalized Graphene Nanosheets with Fewer Defects Prepared via Sodium Alginate Assisted Direct Exfoliation of Graphite in Aqueous Media for Lithium-Ion Batteries

We proposed a cost-efficient method to produce graphene nanosheets from graphite by using a high shear mixer in an aqueous sodium alginate (SA) solution. The results from transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis revealed that the graphite was successfully exfoliated into graphene nanosheets, the obtained graphene was modified by SA after exfoliation, and improved dispersion in water was achieved. The concentration of graphene could attain 0.60 mg/mL at a graphite concentration of 15 mg/mL. When used as nanofiller, significant increases of 65% and 73% in the tensile strength and storage modulus, respectively, of poly(vinyl alcohol) were achieved by incorporating only 0.5 wt % graphene nanosheets. When the exfoliated graphene was applied as an electrode material for lithium-ion batteries, a high initial reversible discharge capacity of 1450 mAh/g was obtained at 100 mA/g, and the capacitive contribution made up ...

Ca 2+ -aided separation of polysaccharides and proteins by microfiltration: Implications for sludge processing

Excess sludge produced by wastewater treatment plants contains extracellular polymeric substances (EPSs; 10–40 dry wt%) that mainly comprise polysaccharides and proteins and can be used as bioflocculants, adsorbents for heavy metal ions, and soil conditioners. Herein, we investigated the separation of EPS constituents using unstirred and stirred dead-end microfiltration in the presence of Ca2+, with an aqueous solution of sodium alginate (SA) and bovine serum albumin (BSA) employed as an EPS model. Acceptable separation efficiencies were obtained utilizing filter papers with micropores of various sizes, which retained calcium alginate aggregates formed due to the SA-Ca2+ interaction but allowed BSA to be filtered out. Notably, a certain minimal Ca2+ concentration was required to achieve the above separation, with the separation efficiency being independent of the SA:BSA concentration ratio at Ca2+ concentrations exceeding the threshold value. The filtration resistance decreased with increasing pore size, Ca2+ concentration, and BSA content. Rather unexpectedly, variation of filtration surface shear could not be used to improve the filtration separation efficiency and reduce fouling in spite of the revolution rate, since the disturbing flow forced the aggregates into the filter pores. The polysaccharide in the EPSs was separated effectively by microfiltration with the addition of Ca2+. Thus, the obtained results provide further insight into the microfiltration-aided separation and recovery of polysaccharides and proteins in EPSs.

Novel procedure for removal of the radioactive metals from aqueous wastes by the magnetic calcium alginate

Upon incorporation of iron oxide particles into calcium alginate gels, composite magnetic materials called ferrogels can be obtained. It has already been found that the alginic ferrogel sorbent can be applied for purification of aqueous solutions containing ions of various heavy metals. In present paper, batch sorption experiments were carried out to remove radionuclides of caesium(I), strontium(II), europium(III) and americium(III) from aqueous solutions. The recovery of the radioactive metals was achieved by direct dosing of sodium alginate/iron carbonyl, followed by stirring the system for 2 h. The process was investigated as a function of the following parameters: pH, initial concentration of calcium ions and the amount of the dispersed iron in the 2% (w/w) aqueous solution of sodium alginate. The optimum conditions were: 15 g/L of iron carbonyl suspended in 1 L of aqueous solution of sodium alginate and about 20 g CaCl2 added to 1 L of the solution containing the radiometals. The results revealed that trivalent Am-241 was totally eliminated. Also trivalent Eu-152/154, divalent Sr-85 and monovalent caesium-137 were removed with the efficiency of about 80, 50 and 30%, respectively. It was found that exchange of calcium chloride with other metal salts does not influence significantly the removal efficiency. Laboratory-scale pilot experiments have shown that with aim to purify water, excess of the gelling agent can be removed with the method of nanofiltration. A one-step procedure for decontamination of liquid radioactive waste has been proposed. Calcium alginate with the inner magnetic core formed from iron carbonyl was found to be effective for aqueous solutions containing Am(III), Eu(III) and Sr(II) radionuclides, while only 30% of Cs(I) was removed in this process. It was demonstrated that there is no need to prepare the sorbent beads prior to the batch sorption.

3D Nanostructured Polypyrrole/Sodium Alginate Conducting Hydrogel from self-assembly with High Supercapacitor Performance

ABSTRACTDue to their possible ideal three dimensional (3D) nanostructures and excellent electrochemical properties, conducting hydrogels have attracted much attention in recent years. Herein, pyrrole monomer was directly dissolved in an aqueous solution of sodium alginate (SA), and was allowed to undergo in-situ polymerization to form polypyrrole (Ppy), resulting in formation of Ppy/SA, a conducting hydrogel, via self-assembly between the polymers. Observation by SEM indicated that the microstructure of the Ppy/SA hydrogel was a typical 3D nano-cylinder network, with the cylinders formed by entanglements of the Ppy and SA molecular chains (cylinder diameter was ∼100 nm). The electrochemical measurements of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy indicated that the Ppy/SA hydrogel possessed typical pseudocapacitance, good charging and discharging rate performance, and favorable capacitive behavior; the specific capacity reached up to 249 F/g at the current density of 0.2 A/g. We suggest it has great potential in the field of high-performance electrode materials for supercapacitors.

MRI investigations of filtration: Fouling and cleaning processes

Fouling and cleaning of hollow fiber membranes were investigated by in-situ magnetic resonance imaging. Two aqueous feed solutions of sodium alginate with and without Ca2+ were applied during dead-end filtration. Loose concentration polarization layers formed during filtration without Ca2+, whereas dense and compact fouling layers were observed in the presence of Ca2+. A major technical concern is cleaning, realized in the two-step process of backwashing and flushing. The concentration polarization layer formed during filtration without Ca2+ was easily removed from the membrane by backwashing. In contrast, the dense and compact layer of alginate with Ca2+ shows an irregular shape and only partly detaches from the membrane during cleaning. The residuals contribute to further membrane fouling in the following process steps. Backwashing and flushing were analyzed by dedicated image processing.

Membrane recovery of alginate in an aqueous solution by the addition of calcium ions: Analyses of resistance reduction and fouling mechanism

Alginate, a sustainable product, can be synthesized by organic substances in wastewater by aerobic granules. Although chemical precipitation is effective for extraction, this typically consumes considerable amounts of chemicals, causing chemical pollution. Alternatively, membrane separation can be used as a potential separation method. Resistance reduction and fouling mechanisms were investigated by constant-pressure dead-end filtration for the membrane recovery of alginate from a suspension formed in an aqueous solution of sodium alginate (SA) by the addition of Ca2+. Flux decline was analyzed by the Ruth's cake filtration theory and the Ruth's filtration coefficient, which indicated that feed filterability exponentially increased as Ca2+ was added. The increased Ruth's filtration coefficient corresponded to decreased concentrations and average specific cake resistances of the components present in the suspension, e.g., colloids and polymers. The optimal amount of Ca2+ should be economically feasible while also affording filtration resistance. Residual Ca2+ in the filtrate can be reused. Residual salt ions increased filtration resistance. The filter cake formed on the membrane was compressible. The effect of protein on the ultrafiltration of alginate was considered. Microfiltration or filtration with a filter paper, exhibiting a high recovery rate of alginate, was suggested.

Preparation of hydroxyapatite/collagen injectable bone paste with an anti-washout property utilizing sodium alginate. Part 1: influences of excess supplementation of calcium compounds.

The anti-washout property, viscosity, and cytocompatibility to an osteoblastic cell line, MG-63, of anti-washout pastes were investigated. Mixing a hydroxyapatite/collagen bone-like nanocomposite (HAp/Col), an aqueous solution of sodium alginate (Na-Alg), which is a paste hardening and lubricant agent, and supplementation of calcium carbonate or calcium citrate (Ca-Cit) as a calcium resource for the hardening reaction realized an injectable bone paste. Adding Ca-Cit at a concentration greater than eight times the Ca2+ ion concentration to Na-Alg improved the anti-washout property. Although the viscosity test indicated a gradual increase in the paste viscosity as the calcium compounds increased, pastes with excess supplementation of calcium compounds exhibited injectability through a syringe with a 1.8 mm inner diameter, realizing an injectable bone filler. Furthermore, the anti-washout pastes with Ca-Cit had almost the same cell proliferation rate as that of the HAp/Col dense body. Therefore, HAp/Col injectable anti-washout pastes composed of the HAp/Col, Na-Alg, and Ca-Cit are potential candidates for bioresorbable bone filler pastes.

Preparation of new photo-crosslinked β-cyclodextrin polymer beads

Photo-crosslinkable groups were introduced to β-cyclodextrin (β-CyD) by the reaction of β-cyclodextrins with isophorone diisocyanate and 2-hydroxyethyl acrylate to produce polysubstituted photo-crosslinkable β-CyD (PSβCyD). To yield PSβCyD of a spherical shape, a suspension consisting of PSβCyD and aqueous sodium alginate solution was added dropwise into an aqueous calcium chloride solution. Then, the PSβCyD macromonomer was photo-crosslinked with ultraviolet radiation to obtain β-CyD polymer beads.

Statistical Modeling Applied to Deformation-Relaxation Processes in a Composite Biopolymer Network Induced by Magnetic Field

This study investigated a methodology based on image processing and statistics to characterize and model the deformation upon controlled and uniform magnetic field and the relaxation under zero field of droplets observed in aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles stabilized by adsorption of citrate ions. The changes of droplet geometry were statistically analyzed using a new approach based on the data obtained from optical microscopy, image processing, nonlinear regression, evolutionary optimization, analysis of variance and resampling. Image enhancement and then image segmentation (Gaussian mixture modeling) processes were applied to extract features with reliable information of droplets dimensions from optical micrographs. The droplets deformation and relaxation trends were accurately adjusted by the Kohlrausch-Williams-Watts (KWW) function and a mean relaxation time was obtained by fitting the time evolution of geometry parameters. It was found to be proportional to the initial radius of the spherical droplets and was associated to interfacial tension.

Aqueous Polyurethane Dispersions - Sodium Alginate Based Blends and Hydrogels

The film forming binary polyurethane-alginate blends and based hydrogels, containing different alginate content, were prepared by blending of anionic polyurethane dispersions (APD) and aqueous sodium alginate (SA) solution. Binary blends of APD and SA were cast in film form from mixed aqueous polymer solutions by solvent evaporation. Post-treatment of as-cast films with CaCl2 leaded tot he hydrogels formation. The thermal stability, thermal transition, water-swelling, mechanical properties and gas permeance for O2 and CO2 of two kinds of films were examined according to alginate content. Irrespective of composition, blend samples gave a single glass transition temperature (Tg), indicating the formation of thermodynamically miscible phase. The shift of Tg in hydrogels to the higher temperatures indicated the possible simultaneous occurrence of a chelate complexation of SA with Ca+2 cations, cross-links between polyurethane chains, having carboxylate anions, with Ca2+ cations, and interactions between SA and anionic polyurethane, resulting in the formation of an semi-interpenetrating network structure. The relationships between the films structure, their physicochemical properties and alginate content have been discussed.

Foundation of technology for obtaining encapsulated oils and prescription development of shells on their basis

The use of sodium alginate and implementation of its chemical potential in the oil encapsulation technology provides thermostable properties of the product shell, which expands the range of new types of oil and fat products with the given geometrical shape, improved consumer properties and extended shelf life. Stable production process of encapsulated oils is ensured by involving a third substance − white sugar into the prescription of an aqueous solution of sodium alginate. Scientific and technological substantiation of structured edible shells of dosed encapsulated oils is provided by the parameters of such systems, which determine the technological cycle of production and operation of special equipment for industrial production. The technology of shells of encapsulated oils, rational concentrations of prescription components are developed. Introduction of white sugar density regulator − at a concentration of 23.0 % into the shell-former solution is substantiated. This helped to determine the organoleptic and structural and mechanical properties E el =(10.0...21.5)×10 3 Pa. Determination of the technological properties of shells of encapsulated oils lays the basis for industrial production, allowing to extend the range of oil and fat raw materials, encapsulated fillers and expand the use of industrial encapsulated products in the catering industry.

The fabrication technique for hollow gel microparticles using microbubble templates

Hollow gel microparticles with shells composed of functional polymer gels are expected to be useful in the production of food additives or anti-reflective films for liquid crystal displays. However, few studies have addressed methods for the simple and efficient production of hollow gel microparticles. Hollow gel microparticles would be expected to find widespread applications if they could be fabricated more easily. In this study, we succeeded in fabricating hollow gel microparticles simply by atomizing a gas-supersaturated aqueous sodium alginate solution into aqueous calcium chloride solution. The gas-supersaturated aqueous sodium alginate solution was prepared by gas pressurization; following a rapid pressure decrease, the excess dissolved gas appeared as microbubbles in the atomized droplets. When the atomized droplets, with encapsulated microbubbles, came into contact with the aqueous calcium chloride solution, the droplets were converted to a gel by ionic crosslinking between sodium alginate and calcium ions, and any remaining bubbles were trapped inside the droplets. With this method, we can fabricate calcium alginate hollow gel microparticles of less than 100 μm with multi-voids. Furthermore, these hollow structures can be controlled by changing the compression pressure, which changes the amount of dissolved gas in the liquid.