Speed Of Phase Separation Research Articles

High permeability poly(vinylidene fluoride) ultrafiltration membrane doped with polydopamine modified TiO2 nanoparticles

Abstract In order to improve the water permeability of poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membranes with low molecular weight cut-off (MWCO), polydopamine (PDA) was employed in the membrane preparation process. Owing to its merits of material-independent adhesion, PDA was coated on inorganic particles or added in coagulation bath to tailor the final membrane structure and property. The introduction of PDA broke through the permeability/selectivity trade-off of the PVDF membrane. By adding the PDA coated titanium dioxide (PDA/TiO2) nanoparticles, water flux increased by 287% while MWCO kept similar with the pristine PVDF membrane. Thermodynamics and Kinetics of the PVDF/additives/non-solvent were analyzed and shown that nanoparticles reduced the thermodynamic stability and increased the phase separation speed, and the speed can be adjusted using different nanoparticles. Additionally, X-ray diffraction (XRD) test indicated that PVDF crystalline form changed from α phase to β phase after adding different nanoparticles. Permeability/selectivity trade-off was broken through by DA addition in coagulation bath. Compared with the original PVDF membrane, when the DA concentration of the coagulation bath was 2.0 g·L−1, water flux increased by 312%, and MWCO of the PVDF membrane ranged in 10,000 to 20,000 Da as well as contact angle decreased from 81.4° to 45°.

The Roles Played by DMF in the Structure Formation of Epoxy-Based Porous Monolith

Epoxy-based porous monoliths are prepared by chemically induced phase separation. The roles played by N,N-dimethylformamide (DMF) in both curing and phase separation kinetics are studied in detail. It is found that the addition of DMF not only changes the speed of phase separation, but the way. Meanwhile, the occurrence of secondary phase separation is partly inhibited, which is in favor of the formation of skeletal network structure. In addition, the schematic pseudo phase diagrams were deduced, which are of great significance to understand the roles played by DMF for the targeted control of materials structure. The results show that by the addition of DMF, the phase diagram moves to the lower right, which means more porogen is needed to obtain skeletal network structure. The spinodal line moves toward the binodal line and the internal space of spinodal line is enlarged. Therefore, it becomes more available to obtain skeletal network structure.

Novel produced water treatment using microemulsion systems to remove oil contents

Produced water (PW) is one of the main sources of oil pollution and it represents the most important environmental concern associated to the oil industry. In this work, microemulsion systems were used to remove dispersed oil from PW. The systems used in the experiments were composed by PW as aqueous phase; kerosene as oil phase; isoamyl alcohol as co-surfactant; and Dissolvan® or Lipesa® as surfactant. An experimental design was applied for process optimization. Experiments were performed according to Scheffé net and showed oil removal efficiencies (%RE) between 24–99%. The microemulsion extraction point used for the process optimization was composed by 60 wt% PW, 5 wt% kerosene, and 35 wt% co-surfactant/surfactant ratio (C/S ratio = 9). The effects of C/S ratio, microemulsion load capacity, oil removal kinetics, temperature, and speed of phase separation were evaluated. From these tests, it was possible to achieve 100% oil removal using C/S = 9, t =25 min, T = 50–60 °C, demonstrating the feasibility of the systems evaluated.

Effects of cooling process on the solid–liquid phase separation process in ultra-high-molecular-weight polyethylene/liquid paraffin blends

Ultra-high-molecular-weight polyethylene (UHMWPE) microporous membrane is generally prepared by thermally induced phase separation process. The phase separation process is closely related to the cooling process in practical production. In this paper, the phase separation temperature of UHMWPE/liquid paraffin blends was explored by the hot-stage-optical device and differential scanning calorimeter (DSC), and the result showed that the temperature was about 105–125 °C. The effects of cooling condition and crystallization ability of UHMWPE on the separation process of the blends were also investigated by DSC. The results showed that the phase separation was affected by the cooling rates rather than the initial cooling temperature. And the crystallization of UHMWPE was mainly limited by the nucleating at a low cooling rate, which could form larger porous structure. In a word, it should be inspirational for the actual production of the UHMWPE microporous membrane. The solid–liquid phase separation will occur in the cooling process of UHMWPE/LP blends, which is driven by the external temperature difference. It is significant to understand the phase separation process. In this paper, the effects of the melting properties and cooling condition on phase separation process were investigated, the S–L phase separation range is at 105–125 °C, and the speed of phase separation is mainly related to the external temperature difference and the UHMWPE content. It could be inspirational for actual production of the UHMWPE membrane with more uniform pore structure.

Modelling of phase separation of alginate-carrageenan gels based on rheology

Application of alginates and carrageenans in food usually include one or the other biopolymer. The combination of the two polymers in gel applications is focus of the present study. Findings not only enhance gel structural understanding, but also enhance biopolymers' fields of application. Structural and rheological properties of mixed alginate/κ-carrageenan, alginate/ι-carrageenan and alginate/furcellaran gels were investigated. Ionic concentration in the gels was set to 50mM K+ and 15mM Ca2+. Based on rheological characterisation, models were utilised to draw conclusions about the gel structure. Mixed gels show phase separation behaviour. The speed of phase separation is dependent on the polysaccharide's sulphate ester content. The fewer sulphate groups present in the carrageenans, the slower phase separation is observed. Alginate/furcellaran gels can be described by an interpenetrating biphasic model, having lower than isostress stability. Alginate/κ-carrageenan gels show phase separation behaviour with counter dilution of the phases and can best be described by a quadratic model. For alginate/ι-carrageenan, a biphasic gel with discrete phase borders, a new model is presented. It is based on a sigmoid function and models the transition from an isostress to an isostrain description.

Ionic Liquid Aqueous Two-Phase Systems for the Enhanced Paper-Based Detection of Transferrin and Escherichia coli.

Aqueous two-phase systems (ATPSs) have been widely utilized for liquid-liquid extraction and purification of biomolecules, with some studies also demonstrating their capacity as a biomarker concentration technique for use in diagnostic settings. As the limited polarity range of conventional polymer-based ATPSs can restrict their use, ionic liquid (IL)-based ATPSs have been recently proposed as a promising alternative to polymer-based ATPSs, since ILs are regarded as tunable solvents with excellent solvation capabilities for a variety of natural compounds and proteins. This study demonstrates the first application of IL ATPSs to point-of-care diagnostics. ATPSs consisting of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and sodium phosphate salt were utilized to quickly concentrate biomarkers prior to detection using the lateral-flow immunoassay (LFA). We found the phase separation speed of the IL ATPS to be very rapid and a significant improvement upon the separation speed of both polymer-salt and micellar ATPSs. This system was successfully applied to both sandwich and competitive LFA formats and enhanced the detection of both Escherichia coli bacteria and the transferrin protein up to 8- and 20-fold, respectively. This system's compatibility with a broad range of biomolecules, rapid phase separation speed, and tunability suggest wide applicability for a large range of different antigens and biomarkers.

Ionophore‐based Heterogeneous Calcium Optical Titration

AbstractRecently, the field of complexometric titration significantly progressed with the advent of ionophore‐based titration reagents. We present here for the first time an ionophore‐based heterogeneous optical titration method for calcium. The all‐in‐one reagent was composed of chromoionophore, ion‐exchanger and calcium ionophore in dichloromethane (DCM). The endpoint of this reverse titration scheme was determined by the color change of the DCM phase (blue to red). The ion‐exchange theory borrowed from ISE membranes was used to simulate the titration curve in a simplified manner. The phase separation speed during titration was found much faster at and beyond the endpoint. A mechanism was proposed for this phenomenon, with zeta‐potential measurements on ion‐selective nanospheres to support the hypothesis. Calcium titration in a urine sample was also successfully demonstrated and compared with EDTA titration with potentiometric ion‐selective electrodes as endpoint indicator. The proposed reagent serves as an alternative to the classical EDTA.

Optical Microscopic Observation of Morphology in Liquid Crystal/Polymer Composites and Their Electro-Optical Properties

We have discovered that bicyclohexyl is suitable for extracting liquid crystals from liquid crystal/polymer composites consisting of a continuous phase of nematic liquid crystal and a three-dimensional polymer network. It was confirmed in optical microscopic observation for the morphology of composites that a polymer structure, observed after extraction of liquid crystals from composites by bicyclohexyl, accorded well with the structure observed by a non-destructive method at a higher temperature than the nematic–isotropic transition point of the liquid crystal. The relationship between the polymer structure in the composite which was evaluated by the non-destructive method and the condition of phase separation induced by photo-polymerization was closely investigated from an aspect of a phase diagram and the speed of phase separation controlled by the intensity of irradiation by UV light. The electro-optical characteristics of the liquid crystal/polymer composite cells were found to be strongly affected by the polymer structure, especially the pore size of the three-dimensional network, which was especially sensitive to the intensity of UV light.

Controlling morphology of polymer microspheres by Shirasu porous glass (SPG) membrane emulsification and subsequent polymerization: from solid to hollow

In this study, the solid, porous, and hollow polymer microspheres were prepared using a simple and novel production method based on Shirasu porous glass (SPG) membrane emulsification and suspension polymerization. With the SPG membrane, uniform-sized emulsion monomer droplets containing divinyl benzene (DVD), styrene (St), hexadecane (HD), and an initiator were prepared in an aqueous phase using a membrane emulsification technique. The aqueous phase contained hydroquinone (HQ) as a water-soluble inhibitor and polyvinylpyrrolidone (PVP) as a stabilizer. The morphology of the particles was affected by the stabilizer, St/DVB ratio, hexadecane amount, and initiator amount. Through this study, the porous polymer microspheres were achieved when the HD content was 30 wt% relative to the monomer and the hollow polymer microspheres was achieved when the HD content was more than 62.5 wt% relative to the monomer. These results highlight the phase separation speed between polystyrene (PSt) and HD.

Coagulation Phase Separation of Solutions of Novel Copolyamides Containing Phthalazinone Moiety

The coagulation phase separation of solutions of novel copoly(phthalazinone amide)s is studied by the cloudpoint titration method. The effects of some factors on the coagulation value (V 1) and critical concentration (C c ) are investigated. It is shown that water is a strong coagulant, having a low coagulation value V 1 and that the V 1 increases with the increase of coagulant concentration and temperature. In addition, an increased percentage of LiCl in the coagulant and of phthalazinone moiety in the polymer main chain can slow down the phase separation speed.

Ultrasonic Assisted Cloud Point Extraction of Polyaromatic Hydrocarbons

Cloud point extraction (CPE) of three PAHs, anthracene, phenanthrene, and pyrene was performed in an ultrasonic environment with Tergitol TMN‐6 as extractant. During the process, surfactant micelle aggregates came out gradually and deposited to form a surfactant‐rich phase. Under the ultrasonic condition, an obvious higher phase separation speed was obtained than the process with heating alone. In the comparison with the conventional cloud point extraction process accelerated by centrifugation, the ultrasonic assisted process offered higher recoveries of the three PAHs with a similar or quicker speed, and relative high recoveries were still preserved even in a high initial PAHs concentration of 60 mg/L. Moreover, the water content in the surfactant‐rich phase obtained by the ultrasonic process was lower than that by the centrifugation process when the surfactant concentration was lower than 2 wt%, leading to a higher preconcentration factor and treatment efficiency in a continuous water treatment process with CPE. Scaling up experiments of the new developed ultrasonic process were performed in the polluted water with different volumes, and recoveries of 80.4%, 92.6%, or 79.3% for anthracene, phenanthrene or pyrene respectively were obtained in 500 mL polluted water, which indicated the process had a great potential to be used in the water treatment in a large scale.

Recovery by solvent extraction of vanadium from spent catalysts leaching solutions using Primene 81R

Recovery of vanadium contained in solutions coming from spent catalysts leaching process by means of solvent extraction techniques using primary amine Primene 81R, has been studied in this work, resulting in an industrial multistage process for the treatment of these effluents. Results obtained allows to propose an extraction mechanism for vanadium(V) with this amine in acidic media, verifying the great influence of pH on the process and fix adequate ranges for variables: O/A ratio, organic phase composition, pH, stirring speed and phase separation speed. These values were simulated in industrial conditions. Vanadium is finally recovered by means of precipitation as ammonium metavanadate and later calcination to obtain vanadium pentoxide of commercial grade.

SOLVENT EXTRACTION OF POLYVANADATES FROM SULPHATE SOLUTIONS BY PRIMENE 81R. ITS APPLICATION TO THE RECOVERY OF VANADIUM FROM SPENT SULPHURIC ACID CATALYSTS LEACHING SOLUTIONS

Recovery of vanadium from a spent catlaysts leaching process has been studied using primary amine PRIMENE 81R, resulting in an industrial multistage process for the treatment of these effluents. An extraction mechanism for V(V) is proposed for this amine in acidic media, verifying the influence of pH on the process. Adequate ranges for the variables: O/A ratio, organic phase composition, pH, stirring speed and phase separation speed were fixed and simulated in industrial conditions. Vanadium is finally recovered by means of precipitation as ammonium metavanadate and later calcination to obtain vanadium pentoxide of commercial grade.

Effects of the Wetting Particles on Phase Separation of Binary Mixtures

We study phase separation of binary mixtures in the presence of mobile particles by the lattice Monte Carlo simulation. The presence of mobile particles changes the morphology of the domain growth, in agreement with earlier experimental result. By varying the wetting interaction strength, we can control the speed of phase separation, and find a critical wetting strength beyond which the growth of the domains slows down. We propose a novel scaling function which describes the growth of the domain size L(t) as a function of time. It suggests an applicable way to tune the speed of phase separation by the coupling between the phase decomposition and the mobile particle-wetting process.

A Study on the Morphology and Electro-optic Properties of Liquid Crystal-Polymer Composite Films

Abstract We have studied the relationship between the morphology and the electro-optic properties of liquid crystal-polymer composite (LCPC) materials. The materials consist of the liquid crystal (80° by weight) and the polymerizable mixture (20° by weight) composed of the monofunctional monomer, the oligomer, and the multifunctional acryl monomer. The results show that the electro-optic properties such as the driving voltage and the transmittance depend strongly on the polymer species used. When the solubility between the liquid crystal and the growing polymers formed during the polymerization process is low and the speed of phase separation is fast, the morphology shows a ‚Network’ type, the liquid crystal exhibits a continuous phase through the sample, and such a film scatters light strongly in the off state. The maximum transmittance in the on state depends primarily on the polymer morphology and secondly on the solubility between the polymers and the liquid crystal in the ‚Network’ type LCPC film. Th...

Early-time spinodal decomposition in the surface layer.

The early stages of spinodal decomposition in the surface layer of a semi-infinite Ising model are studied by using the theory of Langer, Bar-on, and Miller and the self-consistent method. It is shown that the speed of phase separation in the surface layer is faster than that in the bulk because of the surface enhancement, and the one-point distribution function in the surface is different from that of the bulk. It is inferred that the surface with a negative enhancement (Cg0) acts as a two-dimensional ``nucleus'' for the phase separation and for forming a ``wetting layer.''

Studies on Aqueous Two Phase Polymer Systems Useful for Partitioning of Biological Materials

ABSTRACTThe two phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) (PEG) are mixed above a critical concentration of a few percent provide a useful medium for the separation of biological cell subpopulations via partition between the top, PEG-rich phase and the liquid-liquid phase boundary. Interfacial tensions of such systems have been measured by the rotating drop technique and found to range between 10−1 and 102 μN m−1 . The tension was found to depend on the length of the tie line describing the system on a phase diagram, via a power law relationship which differed depending on the concentration of Na phosphate buffer present. The electrokinetic properties of drops of one phase suspended in the other were studied for a variety of systems. It was found that the droplet electrophoretic mobility increased monotonically with phosphate concentration and drop diameter but exhibited the opposite sign from that anticipated from phosphate partition measurements. It was possible to take advantage of these electrokinetic properties and dramatically enhance the speed of phase separation through application of relatively small electric fields.