Effect Of Coagulation Bath Temperature Research Articles

Phase-Field Simulation of the Effect of Coagulation Bath Temperature on the Structure and Properties of Polyvinylidene Fluoride Microporous Membranes Prepared by a Nonsolvent-Induced Phase Separation.

We used the phase-field model of the existing Nonsolvent Induced Phase Separation (NIPS) method to add the variable of temperature in simulating the changes in the process of membrane formation. The polyvinylidene fluoride (PVDF) membrane system was applied to examine the influence of coagulation bath temperature change on the skin-sublayer of the membrane structure, thereby elucidating the development process of membrane structure under different conditions and shedding light on the most suitable coagulation bath temperature ranges. It was found that as coagulation bath temperature increased, the number of interface pores in the outer skin layer decreased, but the size increased. As a result, it changed from the crack shape to round-hole shape, thus making the pore structure looser. In the sublayer, the mesh support structure was increased, which enhanced the mechanical strength of the membrane. Relevant experiments also verify the effectiveness of the model.

Development of High Flux Nanocomposite Polyphenylsulfone/Oxidized Multiwalled Carbon Nanotubes Membranes for Ultrafiltration Using the Systems with Critical Solution Temperatures.

The study deals with the investigation of the effect of the modification of polyphenylsulfone (PPSU) flat sheet membranes for ultrafiltration using oxidized multiwalled carbon nanotubes (O-MWCNT) in order to enhance membrane permeability and antifouling performance. The effect of O-MWCNT loading to the PPSU-polyethylene glycol (PEG-20,000, Mn = 20,000 g·mol−1)-polyvinylpyrrolidone (PVP K-30, Mn = 40,000 g·mol−1)-N-methy-2-pyrrolidinone (NMP) colloid systems on the phase state and viscosity was studied. It was found that PPSU-PEG-20,000-PVP K-30-O-MWCNT-NMP colloid systems feature a gel point (T = 35–37 °C) and demixing temperature (T = 127–129 °C) at which two bulk phases are formed and a polymer system delaminates. According to the study of the phase state and viscosity of these colloid systems, a method for the preparation of high flux PPSU membranes is proposed which includes processing of the casting solution at the temperature higher than gel point (40 °C) and using a coagulation bath temperature lower than gel point (25 °C) or lower than demixing temperature (40 °C and 70 °C). Membrane structure, topology and hydrophilic-hydrophobic balance were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. The effect of coagulation bath temperature and O-MWCNT concentration on the membrane separation and antifouling performance in ultrafiltration of human serum albumin and humic acids solutions was studied. It was found that the modification of PPSU ultrafiltration membranes by O-MWCNTs yielded the formation of a thinner selective layer and hydrophilization of the membrane surface (water contact angle decreased from 53–56° for the reference PPSU membrane down to 33° for the nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT). These changes resulted in the increase in membrane flux (from 203–605 L·m−2·h−1 at transmembrane pressure of 0.1 MPa for the reference membrane up to 512–983 L·m−2·h−1 for nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT depending on coagulation bath temperature) which significantly surpasses the performance of PPSU ultrafiltration membranes reported to date while maintaining a high level of human serum albumin rejection (83–92%). It was revealed that nanocomposite membrane demonstrated better antifouling performance (the flux recovery ratio increased from 47% for the reference PPSU membrane up to 62% for the nanocomposite membrane) and higher total organic carbon removal compared to the reference PPSU membrane in humic acids solution ultrafiltration.

Preparation of hydrophilic modified polyvinylidene fluoride (PVDF) ultrafiltration membranes by polymer/non-solvent co-induced phase separation: effect of coagulation bath temperature

Abstract Membrane separation technology is widely used in wastewater purification, but the issue of membrane fouling could not be ignored. Hydrophilic modification is an effective method to reduce membrane fouling. Therefore, in this work, a hydrophilic modified polyvinylidene fluoride (PVDF) ultrafiltration membrane was prepared by polymer/non-solvent co-induced phase separation, and the effect of coagulation bath temperature on the membrane structure and performance was systematically investigated based on the previous study. With the increased of the coagulation bath temperature, the phase separation process changed from delayed to instantaneous, and the membrane surface changed from porous to dense, while the macropore structures and sponge-like pores appeared on the cross-section. Meanwhile, the pure water flux decreased from 229.3 L/(m2·h) to 2.08 L/(m2·h), the protein rejection rate increased from 83.87% to 100%, and the surface water contact angle increased from 63° to 90°. Thus, excessively high coagulation bath temperature adversely affected the permeate and separation performance, as well as antifouling performance of the membrane. This study enriched the research for preparing separation membranes by polymer/non-solvent co-induced phase separation and provided a practical and theoretical reference for controlling the membrane structure and properties by changing the coagulation bath temperature.

Influence of Coagulation Bath Temperature on the Structure and Dielectric Properties of Porous Polyimide Films in Different Solvent Systems.

In this work, the effect of coagulation bath temperature in different solvent systems [1,4-butyrolactone (GBL)/N,N-dimethylacetamide (DMAC)] on the structure and dielectric properties of polyimide (PI) films was investigated for the first time. The solubility parameter was introduced to explain the formation process of porous PI films. The results showed that the changed tendency of the dielectric constant versus temperature is opposite for the single-solvent system and cosolvent system. For a single DMAC and GBL solvent, the dielectric constants of the films decreased with increasing temperature. In contrast, the dielectric constants increased with the increase in temperature for the GBL/DMAC cosolvent system. Moreover, the measured porosities were applied to estimate the dielectric constants of the PI films. This showed that the porosity increased with increasing temperature for a single-solvent system, while it decreased for a cosolvent system. Scanning electron microscopy images suggested that the variation trends are derived from the different influences of the temperature on the structure and morphology. Thus, this study reveals the effect of coagulation bath temperature on the structure and dielectric properties of porous PI films and provides the guidance for the design and optimization of architectures for high-performance porous films.

Effect of Coagulation Bath Temperature on Mechanical, Morphological, and Thermal Properties of Cellulose/Antarctic Krill Protein Composite Fibers.

Cellulose (C) and Antarctic krill protein (AKP) were dissolved at low temperature, and then C/AKP composite fibers were prepared by wet spinning. In this paper, the effect of coagulation bath temperature on the properties of C/AKP composite fibers were studied by FT-IR, XRD, DSC, and other tests. The results showed that, when the temperature of the coagulation bath increased from 5 to 25 °C, the intermolecular hydrogen bond content of the C/AKP composite fibers increased from 28.20% to 31.33%. When the coagulation bath temperature is 15 °C, the breaking strength of the composite fibers is 1.64cN/dtex, which is 12% higher than that of the composite fibers at room temperature. At this temperature, the crystallinity of the composite fibers is improved, the thermal stability is slightly improved, and the surface morphology is smoother. Inspiringly, when zinc sulfate is added to the coagulation bath, the formation process of the fibers is milder. Moreover, the C/AKP composite fibers have excellent antibacterial activity against Escherichia coli and Staphylococcus aureus.

Effect of Precipitation Temperature on the Properties of Cellulose Ultrafiltration Membranes Prepared via Immersion Precipitation with Ionic Liquid as Solvent.

Supported cellulose ultrafiltration membranes are cast from a cellulose-ionic liquid solution by the immersion precipitation technique. The effects of coagulation bath temperature and polymer concentration in the casting solution on the membrane morphology, wettability, pure water flux, molecular weight cut-off, and fouling resistance are studied. Scanning electron microscopy, contact angle measurements, atomic force microscopy, and filtration experiments are carried out in order to characterise the obtained ultrafiltration cellulose membranes. The results show the effect of coagulation bath temperature and polymer concentration on the surface morphology and properties of cellulose ultrafiltration membranes. Optimisation of the two parameters leads to the creation of dense membranes with good pure water fluxes and proven fouling resistance towards humic acid water solutions.

Effect of coagulation bath temperature during preparation of PES hollow fiber supported liquid membrane for acetic acid removal

<p>Acetic acid is a byproduct of acid hydrolysis of biomass during sugar recovery step in biofuel production. Acetic acid can inhibit the enzyme used during fermentation of sugar to the ethanol. Hollow fiber supported liquid membrane (SLM) was used in this study to remove acetic acid from aqueous solution. Liquid membrane was formulated using trioctylamine and 2-ethyl hexanol as a carrier and solvent, respectively. The hollow fiber membrane support was prepared from 15 wt.% polyethersulfone, 42.5 wt.% polyethyleneglycol 200 and 42.5 wt.% dimethylacetamide. The effect of coagulation bath temperature (CBT) at 30<sup>º</sup>C, 40<sup>º</sup>C and 50<sup>º</sup>C during hollow fiber membrane spinning process was investigated. The porosity of the membrane increased as the CBT increased. The porosity of the membrane prepared using CBT of 30ºC, 40<sup>º</sup>C and 50<sup>º</sup>C were 35.7%, 46.7% and 61.6%, respectively. SLM process using hollow fiber membrane prepared at 50ºC of coagulation bath was able to remove 52% of acetic acid from the aqueous solution.</p><p>Chemical Engineering Research Bulletin 19(2017) 118-122</p>

Effects of Coagulation-Bath Temperature on the Formation Process of PVDF-g-PNIPAAm/poly(NIPAAm-co-AAc-L-Phe) Membrane

In this work, poly (vinylidene fluoride)-graft-poly (N-isopropylacrylamide) (PVDF-g-PNIPAAm) thermo-sensitive polymer and poly (NIPAAm-co-AAc-L-Phe) chiral micro-gels were synthesized firstly. A chiral thermo-sensitive membrane for phenylalanine separation of the racemic mixture was prepared by phase inversion method with the blend of poly (NIPAAm-co-AAc-L-Phe) and PVDF-g-PNIPAAm. The blend membrane formation mechanism of the casting solutions in water bath thermodynamics at different temperatures and the process of membrane formation were investigated via cloud point determination and ultrasonic time-domain reflectometry (UTDR). The results showed that the inversion between hydrophilicity and hydrophobicity of PNIPAAm contributed to the membrane formation process. From the time needed in membrane forming recorded by ultrasonic signal spectra, it can be found that the speed for solidification was increased when the coagulation-bath temperature was higher than 30°C.

Effects of coagulation bath temperature on structure and performance of poly (vinyl butyral) hollow fiber membranes via thermally induced phase separation

Poly (vinyl butyral) (PVB) hollow fiber membranes were fabricated via thermally induced phase separation (TIPS). The effects of coagulation bath temperature (CBT) on the structure and performance of membranes were investigated in detail. The morphologies of the membranes were studied by scanning electron microscopy (SEM), the performances of water permeability, rejection, breaking strength and elongation were measured, respectively. The results indicate that all the membranes have the asymmetric morphology and the thickness of the skin layer decreases and the pore size of the outer layer increases with the increase of CBT. The permeability of membranes prepared at air gap 1.0 cm and take-up speed 0.253 m/s increases from 1.047×10−7 to 5.909×10−7 m3/(m2·s·kPa) with the CBT increasing from 20 °C to 40 °C, and sharply increases to 35.226×10−7 m3/(m2·s·kPa) once the CBT arrives at 50 °C. While the carbonic ink rejections have no significant decrease, totally exceed 98%, but that of acid-maleic acid copolymer greatly decreases with the increase of CBT. Both the breaking strength and elongation decrease with the increase of CBT.

Effects of coagulation bath temperature on polyurethane-based hollow fiber membrane morphology

Polyurethane-based hollow fiber membranes were prepared via melt-spinning method. Effects of coagulation bath temperature (CBT) on membrane outer surface and inner surface morphology were studied in detail by image analysis software. Based on the SEM images, membrane surface pore diameter and porosity were calculated, whereas the interconnected pore size and its distribution were determined using capillary flow porometer. Results show that increasing CBT could improve the membrane outer surface porosity at least twice. Thinner hollow fiber membrane with larger inward water flux could be prepared at higher CB-I (the first coagulation bath) temperature. Higher CB-II temperature (the second coagulation bath) could cause pore contraction and reduce the average diameter of outer surface pore. CBT in the early stage controlled the obtained membrane pore size and its distribution.

Effect of coagulation bath conditions on the morphology and performance of PSf membrane blended with a capsaicin-mimic copolymer

In this study, asymmetric polysulfone (PSf) membranes with capsaicin-mimic groups were prepared from PSf/P(H-M)/DMAc system via phase inversion induced by immersion precipitation. Effects of coagulation bath temperature and composition on morphology, wettability, pure water permeability (Lp), separation performance and anti-fouling property of the prepared membranes were systematically studied by scanning electron microscopy, contact angle measurement and fouling–filtration experiments. The results demonstrated that the elevation in the coagulation bath temperature resulted in greater formation of macrovoids and lower surface hydrophilicity, which attributed to higher both pure water permeability and permeation flux for filtration of HA solution, yet lower both HA rejection and anti-fouling capacity. Either ethanol or glacial acetic acid with different concentrations was used as non-solvent coagulation bath in this study. It was shown that pores on the membrane surface changed larger in size and then obviously shrank with an increase in either ethanol or GAA concentration in the testing range, while the surface hydrophilicity of the membranes was gradually enhanced. When 25% ethanol solution was used in coagulation bath, the membranes exhibited the excellent permeability, separation performance as well as anti-fouling capacity. Moreover, ethanol has several advantages over GAA on the fabrication of the membranes with higher hydrophilicity, permeability, permeation flux and anti-fouling capacity, while GAA favors the improvement in HA rejection of the membranes. On the whole, adjusting coagulation bath condition is an effective approach to tailor the separation performance and anti-fouling capacity of the formed P(H-M)-containing PSf membranes.

Effects of Coagulation-Bath Temperature And Montmorillonite Nanoclay Content on Asymmetric Cellulose Acetate Butyrate Membranes

AbstractA major problem with polymeric membranes is low hydrophilicity and consequently a tendency to fouling. Preparing composite membranes is one way to improve the properties and performance of the neat membrane. In the present study, the effects of coagulation-bath temperature (CBT) and the hydrophilic nanoclay concentration of montmorillonite (MMT) on the morphology and performance of asymmetric cellulose acetate butyrate (CAB) membranes were investigated. The membranes were prepared via phase inversion induced by immersion precipitation in a water-coagulation bath. The morphology of the membranes prepared was studied by scanning electron microscopy (SEM). The permeation performance of the membranes prepared was studied by experiments using pure water and bovine serum albumin (BSA) solutions as feeds. The results showed that the membrane thickness and pure water flux (PWF) were increased by adding up to 2 wt.% MMT nanoclay to the casting solution. These two parameters decreased with further addition of MMT, however. In addition, the results obtained in the case of filtration of BSA solution indicated that the addition of MMT in the casting solution increased permeate flux and reduced BSA rejection slightly. Furthermore, increasing the MMT nanoclay concentration in the casting solution increased pure water flux recovery and consequently decreased the fouling. Decreasing the CBT in the presence of MMT during membrane preparation resulted in the formation of a more porous structure and consequently increased the flux and simultaneously decreased the BSA rejection.

Investigation of membrane preparation condition effect on the PSD and porosity of the membranes using a novel image processing technique

ABSTRACTA totally computerized image processing program package is developed to analyze the SEM images of membrane surface and cross‐section. Pore size distribution and porosity of the fabricated membranes are determined using the proposed image processing procedure. Furthermore, effect of coagulation bath temperature on the morphology and mechanical properties (such as tensile strength, strain break, tensile energy absorbent, and tensile stiffness) of Polysulfone (PSf) membranes are investigated. The results reveal that the mechanical properties are higher when N‐methyl‐2‐pyrrolidone (NMP) is used as solvent. Also, an increase in the coagulation bath temperature caused a monotonous increase in the mean pore size value of Dimethylformamide (DMF)‐based membranes. However, mean pore size curve has a maximum when NMP is used as solvent. Also, porosity of the fabricated membranes increased when coagulation bath temperature increased. For the NMP‐base membranes, pore's diameter was in the range of 0–5 μm. However, DMF‐based membranes have pore size value of smaller than 1 μm when the precipitation medium is kept at 8°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39899.

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.

Effects of coagulation bath temperature on performances of polyethersulfone membranes modified by nanosilver particlesin situreduction

In this work, an in situ reduction method was used to prepare nanosilver-modified polyethersulfone (PES-Ag) ultrafiltration membranes by mixing up the reducing agent ethylene glycol and the protective agent polyvinylpyrrolidone to reduce AgNO3 in the casting solution. The effects of coagulation bath temperature (CBT) on the separation performances, antifouling property, tensile strength, and stability of the nanosilver particles were researched. The results indicated that when the PES-Ag membranes were prepared in 40°C coagulation bath, the loss rate of nanosilver particles during preparation was minimum, only 18.5%. With the CBT increasing from 20 to 60°C, the water flux of the PES and PES-Ag membranes increased, whereas the rejection rate decreased. The largest flux reached 471 L·m−2·h−1 for PES-Ag membranes prepared at 60°C and the rejection was over 90%. The results of contact angle and flux recovery ratio showed that PES-Ag membranes had better hydrophilicity and antifouling property. Furthermore, the PES-Ag membranes could inhibit Escherichia coli from growing. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

A Novel Polyethersulfone Flat Sheet Membrane Prepared from a Lower Critical Solution Temperature System

Polyethersulfone (PES) flat sheet membranes were prepared via phase inversion induced by immersion precipitation from a novel lower critical solution temperature (LCST) system containing PES, 1-butanol and N, N-dimethylacetamide. And the effect of coagulation bath temperature on the properties and structure of PES membranes were investigated. The results show that the pure water flux increases and the tensile strength decreases as the coagulation temperature increases form 20°C to 50°C. Besides, the SEM images shows that all of the membranes prepared from a LCST system at different CBT own sponge-like structures.

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

Thermoporometry study of coagulation bath temperature effect on polyacrylonitrile fibers morphology

The effect of coagulation bath temperature on the morphology of wet-spun polyacrylonitrile fibers was investigated by scanning electron microscopy and thermoporometry, a calorimetric technique based on lowering liquid triple point temperature inside the pores. Fibers were fabricated at two coagulation bath temperatures of 5 °C and 60 °C. The shape of nascent fibers cross-section transforms from bean to circular and pore size increases with coagulation temperature. Porosity parameters including average pore size and pore size distribution, pore volume and internal surface area were determined by thermoporometry. The average pore size and pore volume of the fibers increase with coagulation temperature. Low heating rate of 0.1 °C/min during thermoporometry measurements is the key parameter to ensure that test conditions are close to equilibrium. This study shows that thermoporometry can be employed to characterize closed meso-porosity of wet-spun fibers inaccessible by other standard porosimetry methods.

Effects of Coagulation Bath Temperature on the Separation Performance and Antifouling Property of Poly(ether sulfone) Ultrafiltration Membranes

Poly(ether sulfone) (PES) ultrafiltration membranes are fabricated via nonsolvent-induced phase separation by blending with hydrophilic homopolymer additive poly(ethylene glycol) (PEG) or amphiphilic block copolymer Pluronic F127. The effects of coagulation bath temperature (CBT) on membrane structure, separation performance, and antifouling property are investigated in detail. All the membranes display an asymmetric morphology. PES/PEG membranes possess only fingerlike pores of support layer, while there is a spongelike sublayer between skin layer and the fingerlike pores for PES/Pluronic F127 membranes. The thickness of the spongelike sublayer for PES/Pluronic F127 membranes is remarkablely decreased with the increase of CBT. For all the membranes, pure water flux increases substantially with the increase of CBT. The rejection of PES/PEG membrane for bovine serum albumin (BSA) is above 95%. However, the rejection of PES/Pluronic F127 membrane for BSA molecules is decreased sharply form 95.3% to 10.2% with the increase of CBT from 20 to 60 °C. At higher CBT, the antifouling capabilities of PES/Pluronic F127 membranes are slightly weakened mainly because of the lower surface coverage of amphiphilic copolymer.