Coagulation Bath Temperature Research Articles

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.

Preparation and performance of sulfonated polysulfone flat ultrafiltration membranes

Sulfonated polysulfone (SPSF) flat ultrafiltration membranes were successfully prepared by immersion precipitation phase inversion method. N‐Methyl pyrrolidone was used as a solvent, and polyvinylpyrrolidone (PVP) was used as a polymeric additive in the casting solution. The effects of casting solution formulation and preparation conditions on membrane structure and properties were investigated in present study, and the morphology of the membranes was analyzed by scanning electron microscopy. The results indicated that the performances of SPSF membranes made by chemical modification were better than polysulfone membrane. The SPSF concentration played a vital role in restricting the pure water flux (PWF), promoting the rejection coefficient, and improving the hydrophilicity. A maximum PWF and minimum egg albumin rejection coefficient were obtained when the PVP content was 10%. When the coagulation bath temperature was set to 25°C, the PWF reached 480 L·m−2·h−1 and the ovalbumin rejection coefficient reached 92%. Longer evaporation times improved the PWF. Specifically, when the evaporation time was 70 s, the comprehensive performance was good. POLYM. ENG. SCI., 55:1003–1011, 2015. © 2014 Society of Plastics Engineers

Preparation of PVDF/PEI double-layer composite hollow fiber membranes for enhancing tensile strength of PVDF membranes

Polyvinylidene fluoride (PVDF) hollow fiber membrane is widely used for water treatment. However, the weak mechanical strength of PVDF limits its application. To enhance its tensile strength, a double-layer composite hollow fiber membrane, with PVDF and polyetherimide as the external and inner layers, respectively, was successfully prepared through phase inversion technique. The effects of additive content, air gap distance, N,N-dimethyl-acetamide content in the inner core liquid, and the temperature of external coagulation bath on the membrane structure, permeation flux, rejection, tensile strength, and porosity were determined. Experimental results showed that the optimum preparation conditions for the double-layer composite hollow fiber membrane were as follows: PEG-400 and PEG-600, 5 wt%; air gap distance, 10 cm; inner core liquid and the external coagulation bath should be water; and temperature of the external coagulation bath, 40 C. A single layer PVDF hollow fiber membrane (without PEI layer) was also prepared under optimum conditions. The double-layer composite membrane remarkably improved the tensile strength compared with the single-layer PVDF hollow fiber membrane. The permeation flux, rejection, and porosity were also slightly enhanced. High-tensile strength hollow fiber PVDF ultrafiltration membrane can be fabricated using the proposed technique.

Effect of Additive on the Performance of PVDF Membrane via Non-Solvent Induced Phase Separation

Poly (vinylidene fluoride) membranes were prepared from the ternary mixture of PVDF/ 1, 2 - propylene glycol/dimethylacetamidevianon-solvent induced phase separation (NIPS). The effect of the addition of the 1, 2 - propylene glycol content, the Coagulation Bath Temperature and the concentration of PVDF on the performance and structure of the PVDF membranes was studied in the present investigation.The results showed that with increasing polymer concentration, the mechanical strength increased,and the structure of membrane changed from finger-like macro-voids structureto sponge-like structure.It was found that water flux, breaking elongation and tensile strength of the membrane increased with increasing 1, 2 - propylene glycol content, when the content reached 41wt.%, the water flux reaches a maximum.The morphology of PVDF can be improved by the addition of 1, 2 - propylene glycol, which was changed from finger-like structure to sponge-like structure. And the dense skin layer of PVDF membranes became thicker with increasing 1, 2 – propyleneglycol. The tensile strength decreasedfrom 3.3 to 2.1MPa, breaking elongation decreased from 315% to 280% andthe pure water flux increased from 91 to 909 L·m-2·h-1. as the coagulation bath temperature (CBT) decreased from 30°C to 5°C.With this condition, the sponge-like hollow fiber membrane hassuccessfully spun.

Morphology Control of Polyimide Fibers by Phase Separation under Different Coagulation Bath Conditions

In order to investigate the effects of the coagulation bath temperature and composition on the formation of polyimide fiber in wet spinning, theoretical ternary phase diagrams of water/NMP/PI system at two coagulation bath temperatures was investigated based on the extended Flory-Huggins theory. The cloud-points data of the system for more dilute PI terpolymer solutions were determined by cloud point titration, and the cloud point data for more concentrated PI terpolymer solutions were calculated by Boom's linearized cloud point curve correlation. The obtained diagrams showed that if the titration process constructed at a higher temperature, the meta-stable two-phase region in the ternary phase diagram increases, which is beneficial for the de-mixing of the filament via nucleation and growth mechanisms, resulting in a homogenous dense structure for PI fiber.

Fabrication of the Colored PMIA Fibers by Wet Spinning: Effect of Spinning Parameters on the Coagulation Process

The poly (m-phenylene isophthalamide) (PMIA) fiber, which can be prepared by wet spinning, is a kind of aromatic polyamide fiber. The spinning parameters could influence the performance and structure of the colored PMIA fiber such as the diffusion coefficient and coagulation bath. In this study, the PMIA spinning solutions doped with Color Inde purple 120 were first commixed in a pressurizer and then spun into a coagulation bath under a pressure about 0.3 MPa. In the coagulation bath, the pure or dope-dyed PMIA fibers were prepared by wet spinning at 323 K, and then the as-spun fibers were extracted by an ultrasonic oscillation method. The effects of jet stretch ratio, temperature, and concentration of the coagulation bath on the ratio of diffusion coefficient of solvent to coagulator were analyzed during the spinning process of dope-dyed PMIA fibers. The properties and structures of the colored PMIA fibers were characterized by SEM. Finally the most optimized spinning technology of the dope-dyed PMIA fiber was obtained and the dope-dyed PMIA fibers were successfully fabricated through wet spinning.

Effect of blend ratio and coagulation bath temperature on the morphology, tensile strength and performance of cellulose acetate/poly(butylene succinate) membranes

In the present study, blend membranes of cellulose acetate (CA)/poly(butylene succinate) (PBS) were prepared. The membrane morphology, tensile strength and performance in bread wastewater treatment were evaluated in terms of the membrane preparation conditions. According to the results, presence of PBS varied the membrane structure by reducing the extension of macro pores in the membrane sublayer. CA could effectively improve tensile strength of the membranes. Reducing coagulation bath temperature resulted in obtaining the membranes with denser structure and also higher tensile strength. Considering differences in surface and cross-sectional structures, the membranes with PBS content of 85 and 100% were found to have the highest separation ability, whereas the highest flux belonged to the membrane with 50% PBS.

Effect of the preparation conditions on the morphology and performance of poly(imide) hollow fiber membranes

ABSTRACTPoly(imide) (PI) hollow fiber membranes were prepared by using classical phase inversion process. Effects of different external coagulation bath temperatures (ECBT) and various bore flow rates (BFR) on the morphology and separation performance of the membranes were studied. Cross‐section, inner and outer structures were characterized by using scanning electron microscope and atomic force microscopy (AFM). Mean pore size, pore size distribution, and mean roughness of the PI hollow fibers surfaces were estimated by AFM. It was found that the hollow fibers morphology composed of sponge‐like and finger‐like structures with different ECBT and BFR. A circular shape of the nodules with different sizes was observed in the outer surface of the PI hollow fibers. Mean pore size of the outer surface increases with increasing ECBT and BFR. The important result observed in this study is that the ECBT clearly has the largest effect on hollow fiber PI membrane roughness compared with the BFR. Pure water permeability of the PI hollow fibers was improved with increase of ECBT and BFR. The solute rejection (R%) was reduced when the ECBT and BFR was increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40428.

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.

Preparation, characterization and gas permeation properties of PDMS/PEI composite asymmetric membrane for effective separation of hydrogen from H2/CH4 mixed gas

In this work, PDMS/PEI membranes were synthesized and sorption and permeation of H2/CH4 mixture were studied. The influence of pressure, temperature and feed composition were investigated. It was shown that permeances increased and selectivity decreased with an increment in the feed temperature. Increasing feed pressure caused a decline in gas permeance and increased selectivity. Higher concentrations of hydrogen in the feed declined the selectivity. The effect of different non-solvents was explained by their effect on precipitation time and it was concluded that water made the membrane denser while isopropanol forms a sponge-like structure. Coagulation bath temperature made the membrane denser. Film casting and dip-coating techniques were used to prepare selective membranes. Obtained selectivity results introduced dip-coating as a better method than film casting. Sequential coating improved selectivity of the prepared membrane. Finally, sequential coating with different concentrations was applied and enhanced selectivity significantly from about 22 to more than 70.

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.

Permeability characterization of hydroxypropylcellulose/ polyacrylonitrile blend membranes

Abstract A series of blend membranes were prepared by immersion precipitation phase inversion method using hydroxypropylcellulose and polyacrylonitrile as raw materials. The effects of casting conditions on membrane’s characterization were studied. The properties of resulting blend membranes were that water flux decreased from 489 L·h-1·m-2 to 312 L·h-1·m-2 ; retention rate increased from 80.1% to 91.8%; and corresponding porosity presented increasing trend but changed little within the range of casting solution concentrations from 10 wt % to 16 wt %. The greater the mass fraction of HPC in casting solution, the greater the water flux of blend membranes. Prolonging the atmosphere exposing time, water flux increased from 268 L·h-1·m-2 about 20s to 372 L·h-1·m-2 about 60 s, then decreased to 340 L·h-1·m-2 about 75s. In addition, retention rate decreased from 91.2% to 81.3%. Porosity tend to decrease but changed a little. With the coagulation bath temperature rising, water flux of blend membranes increased from 306 L·h-1·m-2 about 20 0C to 429 L·h-1·m-2 about 35 0C, and corresponding retention rate decreased from 87.9% to 82.5%, porosity decreased from 80.23% to 68.26%.

Preparation of porous membrane by combined use of thermally and chemical reaction-introduced nonsolvent-induced phase separations

Microporous polyacrylonitrile membranes were prepared via the combination of thermally and chemical reaction-introduced nonsolvent-induced phase separations (TIPS and CRINIPS). In the membrane preparation, glacial acetic acid (GA) and aqueous solution of 2 wt.% sodium bicarbonate were used as additive and coagulation media, respectively, and chemical reaction between GA and sodium bicarbonate resulted in uniform microporous membranes. Pore connectivity and asymmetry were significantly improved when coagulation bath temperature was lowered to 15°C. The fouling mechanisms of the prepared membrane were analyzed by nonlinear regression method and cake filtration model was the most appropriate for the membrane prepared via combining TIPS and CRINIPS. The pore structure was made connective and asymmetric by using a 15°C aqueous solution of 2 wt.% sodium bicarbonate as coagulation media in membrane precipitation process, and the average pore size reduced from about 0.125 to 0.097μm while decreasing the glass plate temperature from 80 to 20°C.

Diffusion Dynamics of HAc from Cellulose Acetate Filament during Coagulation Process

During dry-wet spinning, diffusion is very important for the formation and mechanical property of fibers. In this paper, the diffusion dynamics of acetic acid (HAc) and water (H2O) during coagulation process of cellulose acetate filament were investigated in detail. The diffusion coefficients of HAc and H2O were calculated based on the Ficks first law of diffusion according to the experimental data. Several factors which affect the coagulation process including concentration and temperature of coagulation bath were discussed respectively. The result showed that the diffusion coefficients of HAc and H2O increased with the increasing coagulation temperature and decreased with the increasing coagulation bath concentration.

Preparation and Performance of Polysulfone Hollow Fiber Ultrafiltration Membranes

Polysulfone (PSF) hollow fiber ultrafiltration membranes were successfully prepared by dry-wet spinning technology. Dimethylacetamide (DMAC) was used as a solvent, water was used as bore liquid and coagulation bath, polyvinylpyrrolidone (PVP) was used as polymeric additive. The effects of spinning conditions on membrane structures and properties were investigated in present study. The results indicated that with the increase of PVP concentration, pure water flux increased and developed finger-like pores were formed. High coagulation bath temperature restricted pure water flux, 30°C was the best for the preparation of high-performance ultrafiltration membranes. When the air length was 11cm, the membrane comprehensive performance was the best.

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.

폴리히드록시아미드 섬유의 제조와 열처리에 따른 구조-물성 상관관계(I) -다양한 고화조건에 따른 고화거동-

Abstract: Polyhydroxyamide (PHA) was synthesized using low temperature solution polymerization of 3,3'-dihydrox-ybenzidine (DHB) and isophthaloyl chloride (IPC) in N,N-dimethylacetamide (DMAc). In order to study wet-spinningof PHA fibers, the diffusion property of DMAc in various coagulants and the effect of coagulation bath temperaturewere evaluated. The initial diffusion rate of DMAc, and the SEM images and mechanical properties of PHA fibers,demonstrated that the coagulation in ethanol at 20 o C was the most optimal among all the conditions examined. Thetensile strength and initial modulus of PHA fibers increased, while its breaking strain decreased with increasing spindraw ratio (SDR). The wide-angle X-ray diffraction (WAXD) experiment revealed that the crystallinity of PHA fibersincreased with increasing SDR. The process-structure-property relationship among PHA fibers under various coagula-tion conditions was also investigated. Keywords: PHA fibers, spinning dope, coagulation bath temperature, coagulants, initial diffusion rate, spin draw ratio

Polyethersulfone/poly (butylene succinate) membrane: Effect of preparation conditions on properties and performance

In this study, biodegradable polymer of poly (butylene succinate) (PBS) was blended with polyethersulfone (PES) to prepare a novel semi-biodegradable membrane. The effect of blend ratio and coagulation bath temperature (CBT) was investigated on membrane characteristics including membrane morphology, mechanical strength and also treatment ability. Moreover, Fourier transform infrared (FTIR) spectrum, thermal stability, biodegradation and contact angle of the membranes were studied. Results demonstrated that the wastewater permeation through the prepared membranes was increased by blending the polymers and reached to maximum at blend ratio of 50/50. The wastewater treatment of PES/PBS blend membranes was improved by increasing PBS content.

Amoxicillin separation from pharmaceutical wastewater by high permeability polysulfone nanofiltration membrane

In this study, high permeability flat sheet polysulfone nanofiltration membranes were prepared for amoxicillin (AMX) recovery from pharmaceutical wastewater. Membrane fabrication includes two steps: raw ultrafiltration membrane synthesis by phase inversion method and nanaofiltration membrane synthesis by surface photopolymerization. Raw ultrafiltration membranes were synthesized using different molecular weights of polyethylene glycol (PEG) as pore former and different coagulation bath temperatures (CBTs). The synthesized ultrafiltration membranes were modified using UV-assisted polymerization technique and their performance in the separation of AMX at different pHs, were studied. The results showed that the more irradiation time, the smaller surface pore size. Moreover, the membranes made with higher molecular weight of PEG and coagulation bath temperatures were more susceptible for UV-modification at these conditions; fabricated membranes had higher flux as well as relatively high AMX separation. Moreover, pH enhancement increased AMX rejection by 85%. The effect of irradiation on membrane surface morphology was studied by SEM surface images and the morphological effects of pore former and coagulation bath temperatures on membrane structure were confirmed by SEM cross section images. A fairly comprehensive discussion about the effects of PEG, coagulation bath temperature and irradiation time on membrane structure and AMX recovery performance was represented in this study.

Modification of PSf membrane nanostructure using different fabrication parameters and investigation of the CO2 separation properties of PDMS-coated PSf composite membranes

The effects of preparation parameters on the performance and morphology of polydimethylsiloxane/ polysulfone (PDMS/PSf) membranes were investigated. The PDMS layer is mainly used for sealing the defects of the PSf selective layer. The membrane morphologies were characterized by using scanning electron microscopy (SEM). The CO2/CH4 separation performance of membranes was studied by a pure gas permeation experimental set up. According to the SEM results, decreasing the water/N,N-dimethylacetamide (DMAc) ratio as the coagulation medium from pure water to mixture of 90 vol.% DMAc and 10 vol.% water resulted in complete disappearance of macrovoids and also a lowering of the membrane selectivity. Permselectivity results showed that the ideal CO2/CH4 separation factor of the membranes was improved by the presence of the non-solvent additive to the polymer solution. It was also observed that reduction of the coagulation bath temperature (CBT) led to elimination of macrovoids which affect gas separation performance. Using methanol as a coagulant resulted in a less selective membrane compared with ethanol and water as coagulants and the CO2 permeance was about 3 and 9 times greater than with ethanol and water as coagulants, respectively.