Microporous Hollow Fiber Membrane Research Articles

Determination of polycyclic aromatic hydrocarbons (PAHs) from organic aerosols using hollow fiber micro – porous membrane liquid – liquid extraction (HF-MMLLE) followed by gas chromatography–mass spectrometry analysis

A method for determination of polycyclic aromatic hydrocarbons (PAHs) from aerosols was developed. Instead of conventionally used non-polar or slightly polar phenylmethylpolysiloxane column a highly polar, highly substituted, cyanopropyl column (VF-23 MS) was used for separation of PAHs. Based on hollow fiber micro-porous membrane liquid–liquid extraction (HF-MMLLE) a method was developed for sample clean up and pretreatment. An enrichment factor of 617–1022 was obtained with extraction efficiency 10.2–18.9% for different PAHs analyzed in this study. The optimized method was successfully applied to aerosol samples and limits of detection between 1.2 pg m −3 and 180 pg m −3 was obtained. Almost all PAHs were found in most of the aerosol samples.

Biological treatment of mixtures of toluene and n‐hexane vapours in a hollow fibre membrane bioreactor

Membrane bioreactors are gaining interest for the control of contaminated air streams. In this study, the removal of toluene and n‐hexane vapours in a hollow fibre membrane bioreactor (HFMB) was investigated. The focus was on quantifying the possible interactions occurring during the simultaneous biotreatment of the two volatile pollutants. Two lab‐scale units fitted with microporous polypropylene hollow fibre membranes were connected in series and inoculated with activated sludge. Contaminated air was passed through the lumen at gas residence times ranging from 2.3 to 9.4 s while a pollutant‐degrading biofilm developed on the shell side of the fibres. When toluene was treated alone, very high elimination capacities (up to 750 g m−3 h−1 based on lumen volume, or 1.25 g m−2 h−1 when normalized by the hollow fibre membrane area) were reached. When toluene and hexane were treated simultaneously, toluene biodegradation was partially inhibited by n‐hexane, resulting in lower toluene removal rates. On the other hand, hexane removal was only marginally affected by the presence of toluene and was degraded at very high rates (upwards of 440 g m−3 h−1 or 0.73 g m−2 h−1 without breakthrough). Overall, this study demonstrates that mixtures of toluene and n‐hexane vapours can be effectively removed in hollow fibre membrane bioreactors and that complex biological interactions may affect one or more of the pollutants undergoing treatment in gas‐phase membrane bioreactors.

Effects of membrane properties on CO2 recovery performance in a gas absorption membrane contactor

Abstract Global warming is a serious global environmental problem. CCS (Carbon dioxide Capture and Storage) is considered to be an emergency measure to mitigate the increase in atmospheric CO 2 . Chemical absorption is the major separation technique employed in CCS. Recently, the focus has been on chemical absorption using a membrane contactor with microporous hollow fibres because of the large contact area between the gas and liquid as well as the absence of problems such as flooding and channelling. In this study, we changed the properties of the polyethylene microporous hollow fibre membranes by two treatments: (i) drawing in the axial direction and (ii) soaking in concentrated nitric acid solution. The effects of these treatments on CO 2 recovery performance were investigated by a CO 2 recovery experiment using the untreated and treated membranes and a MEA aqueous solution. The CO 2 recovery rate for the membrane treated by drawing was higher than that for the untreated membrane. Additionally, the CO 2 recovery rate increased with an increase in the drawing ratio. The nitric acid treatment also increased the CO 2 recovery rate compared with the untreated membrane. Changes in membrane dimensions, porosity and pore size distribution were expected to be major reasons for the increase in CO 2 recovery rate for the membrane treated by drawing. On the other hand, nitric acid treatment did not induce any changes in membrane dimensions or pore size distribution but only reduced the surface roughness. As a result, the decrease in surface roughness was a major reason for the increase in CO 2 recovery rate for the membrane treated with nitric acid.

Hollow-Fiber Microporous Membrane Liquid-Liquid Extraction for Determination of Polybrominated Diphenyl Ethers at Trace Levels in Sewage Sludge with Gas Chromatography-Electron Capture Detection

A two-phase hollow-fiber (HF) liquid-phase microextraction (LPME) method followed by gas chromatography was developed for quantification of 8 major polybrominated diphenyl ethers at trace level in sewage sludge. In this method the porous polypropylene hollow fibers filled with a few microliters of organic solvent, were immersed in aqueous samples of wet sludge which were spiked with the PBDEs at ng/l level. Parameters such as salt concentration, stirring speed, extraction time and pH were optimized and the optimum extraction conditions were then applied to the determination of PBDEs in sewage sludge from Kallby sewage treatment plant in Lund. The optimized method allowed detection of 5.1 µg kg–1 and 0.43 µg kg–1 of BDE-47 and 183, respectively, in dried sludge. The findings were compatible with the results from recent research on PBDEs level in sewage sludge samples from Sweden. Although BDE-209 was expected to have the highest level, it was not detected. Limit of detection, photodegradation or/and biodegradation of BDE-209 during treatment or experiment are major reasons. Low organic solvent consumption, low sample volume requirement, high preconcentration factor, simplicity without using expensive instrument for extraction and excellent sample clean-up are some important factors that make this sample preparation technique very useful for determination of PBDEs in sludge.

Effect of polyethylene glycol (PEG) as an additive on the fabrication of polyvinylidene fluoride- co-hexafluropropylene (PVDF-HFP) asymmetric microporous hollow fiber membranes

Polyvinylidene fluoride- co-hexafluropropylene (PVDF-HFP) has received much attention recently as a promising membrane material for membrane contactor application. A systematic study has been carried out to investigate the effects of polyethylene glycol (PEG) with different molecular weights and different loadings as an additive on the fabrication of PVDF-HFP asymmetric microporous hollow fiber membranes. Moreover, the synergetic effects of coagulation temperature and the second additive (lithium chloride: LiCl) with PEG are also evaluated. Experiments revealed that the addition of PEG into the PVDF-HFP/NMP solution resulted in the system thermodynamically less stable in reaction with water, promoting rapid phase demixing in the phase inversion process. When the same 3 wt% PEG was added into the dope solution, the dimension of finger-like macrovoids of the resultant membrane increased in parallel with the increase of PEG molecular weight from 200 to 600 and 6000 kDa, and pure water permeability (PWP) also increased accordingly. An increase in PWP was also observed when PEG-200 loading in the dope solution was increased from 3 to 5 and 10 wt%, corresponding to the morphology change of resultant membranes. As a synergetic effect of coagulation temperature with PEG, the finger-like pores occurred in the membrane at room temperature expanded to much larger macrovoids using 10 °C water as the coagulant, and the big finger-like pores almost disappeared when the coagulation bath temperature was increased to 40 °C because of delayed phase demixing. The big macrovoid size can also be suppressed by adding the second small molecule additive, LiCl, due to its strong interactions with NMP and PVDF-HFP to delay the dope precipitation. The irregular inner contour of the membrane can be eliminated by the increase of coagulation bath temperature to 40 °C. The hollow fiber membrane made by a dope of PVDF-HFP/PEG-6000/LiCl/NMP (15/3/3/79 in weight) using 40 °C water as the coagulant exhibited a high PWP of 117 L/m 2 h atm and reasonably good MWCO of 150 kDa. An improvement has been made in the current work as compared to previous PVDF-HFP hollow fiber membranes reported in literatures.

Oxygen transfer characteristics of hydrophilic treated polypropylene hollow fiber membranes for bubbleless aeration

Bubbleless membrane aeration is a promising method for water oxygenation. In this work, the oxygen transfer characteristics of hydrophilic treated polypropylene (PP) microporous hollow fiber membranes were studied. Both cross flow and parallel flow modules were used for the bubbleless aeration of water with operating pressures up to 100 kPa. An intermittent degassing process was used in the aeration operation to maintain high oxygen transfer. A correlation was developed to evaluate the membrane resistance at different pressures. It was found that with an increase in operating pressure from 20 to 100 kPa, the membrane resistance decreased almost linearly from 8.8 × 10 4 to 4.6 × 10 4 s/m and from 4.0 × 10 4 to 2.1 × 10 4 s/m in cross flow and parallel flow, respectively. At appropriate operating pressures, the membrane resistance for hydrophilic treated PP membranes was similar to dense and composite membranes, while only one-third of the resistance of hydrophilic polysulfone membranes. Mass transfer was correlated with the Reynolds number over the range of operating pressures. The correlations obtained in this study are in agreement with previously reported correlations at a low Reynolds number.

Preparation and characterization of poly(vinyl butyral) hollow fiber membrane via thermally induced phase separation with diluent polyethylene glycol 200

Hydrophilic poly(vinyl butyral) (PVB) microporous hollow fiber membranes were prepared via thermally induced phase separation (TIPS), polyethylene glycol with molecular weight 200(PEG200) was used as diluent. The phase diagram of PVB/PEG200 system indicated L–L phase separation. The effects of preparation condition such as take-up speed, bore liquid flow rate, air-gap, and water bath temperature on the properties of the membrane were investigated. The results showed that PVB hollow fiber membrane prepared at air-gap 5 mm had a little greater tensile strength, breaking strength and elongation than those prepared at air-gap zero, and the former had a little greater rejection but smaller water permeate. The increase of the take-up speed led to the decrease of inner diameters and thickness, the increase of the bore liquid flow rate led to the increase of inner diameter and outer diameter, but the decrease of thickness.

Surface modification of polypropylene membrane to improve antifouling characteristics in a submerged membrane-bioreactor: Ar plasma treatment

To improve the antifouling characteristics of polypropylene hollow fiber microporous membranes in a submerged membrane-bioreactor for wastewater treatment, the surface-modification was conducted by Ar plasma treatment. Surface hydrophilicity was assessed by water contact angle measurements. The advancing and receding water contact angles reduced after the surface modification, and hysteresis between the advancing and receding water contact angles was enlarged after Ar plasma treatment due to the increased surface roughness after surface plasma treatment. After continuous operation in a submerged membrane-bioreactor for about 55 h, the flux recovery after water cleaning and the flux ratio after fouling were improved by 20.0 and 143.0%, while the reduction of flux was reduced by 28.6% for the surface modified membrane after 1 min Ar plasma treatment, compared to those of the unmodified membrane. Morphological observations showed that the mean membrane pore size after Ar plasma treatment reduced as a result of the deposition of the etched species; after it was used in the submerged membrane-bioreactor, the further decline of the mean membrane pore size was caused by the deposition of foulants. X-ray photoelectron spectroscopy and infrared spectroscopy confirmed that proteins and polysaccharide-like substances were the main foulants in the precipitate.

Preparation and Characterization of Microporous Hollow Fiber Membranes Containing Hydrotalcite as an Inorganic Adsorbent

Preparation and Characterization of Microporous Hollow Fiber Membranes Containing Hydrotalcite as an Inorganic Adsorbent

Model of a polyethylene microporous hollow-fiber membrane biofilm reactor inoculated with Pseudomonas putida strain To1 1A for gaseous toluene removal

A diffusion and reaction model is presented for a gas phase membrane biofilm reactor (MBfR) that overcomes many of limitations of conventional biofilters. The model considers transfer of toluene from the gas phase through the membrane and into a toluene degrading biofilm. Data from bench-scale tests of toluene removal in an MBfR were used to validate the model. Overall mass transfer coefficients were 0.64 × 10 −3, 1.1 × 10 −3, 1.86 × 10 −3 (m s −1) at liquid flow rates (shell-side) of 4, 7, and 9 L min −1, respectively. Modeled mass transfer coefficients were in good agreement with experimental values. The bench-scale MBfR was capable of removing more than 98% of the influent toluene (an overall removal rate of 17 g m −3 min −1) at an inlet concentration of 100 ppm v and a gas flow rate of 1.0 L min −1 (gas residence time of 1.3 s in the membrane lumen). Model predictions were well in agreement with experimental values.

Hollow fiber membrane supported thin liquid film extraction for determination of trace phenoxy acid herbicides and phenols in environmental water samples

Traces of phenoxy acid herbicides and phenols were determined in environmental water samples by high performance liquid chromatography (HPLC) coupled to thin liquid film extraction (TLFE). A TLFE sampling device was prepared by dipping pieces of a polypropylene microporous hollow fiber membrane into dihexyl ether (containing 10% tri-n-octylphosphine oxide as carrier) for a few minutes to impregnate the pores of the hollow fiber wall. Extraction of analytes takes place from the outer aqueous phase into the immobilized solvent. After extraction the removal of the organic solvent was accomplished with a few µl of methanol which was used for HPLC analysis. Enrichment factors as high as 446 were obtained for the target compounds. The method provided detection limits as low as 0.4–1.2 µg L−1, good repeatability (the RSD ranging from 2.1 to 6.3%, n = 5) and a linear range from 2 to 200 µg L−1 for the target compounds. Real sample analysis showed recoveries between 84.6% and 112% for all compounds investigated.

Observation of cake layer formation and removal on microporous hollow-fibre membranes

The cake layer in submerged membrane bioreactor (sMBR) processes is leading to an additional flow resistance and it is through this that the long-term filtration performance of the system is af fected. Therefore, air is injected into the suspension to induce flow and to generate shear in order to partly remove the cake layer. Furthermore, the bubble-induced movement of hollow-fibres has been identified to significantly improve the shear production with air bubbling . Hence, this paper will report about experiments conducted on different scales and in different operating modes including novel magnetic resonance imaging (MRI) techniques to visualise the cake layer and quantify the local permeate production. Within the first part of this study, experiments have been performed with a number of model substances to characterise the impact of operating parameters on the filtration performance of stationary hollow-fibre membranes of the PURON® system. The setup consists of a tubular test cell equipped with a single hollow-fibre and is operated with a constant TMP in cross-flow mode without air bubbling. Suspensions containing silica particles of different particle size distributions dispersed in solutions of xanthan gum, with different dynamic viscosities, were filtrated for approximately 30 min while the permeate flux was measured. It was shown that the dynamic viscosity and the shear thinning characteristics of the suspensions are similar compared to established viscosity models of activated sludge . Moreover, the filtration tests have shown that the long-term permeate flux is increasing with an increasing cross-flow velocity, a decreasing solids concentration, a decreasing average particle size and an increasing dynamic viscosity, whereas the long-term permeate flux is independent from the feed pressure. These trends are consistent with published theories which demonstrate that the thickness of the reversible cake layer increases with a decreasing cross-flow velocity and an increasing feed pressure. While an increase in cross-flow velocity is leading to an enhanced entrainment of deposited matter, and thereby to a higher permeate flux, a higher feed pressure is leading to a temporary increase in permeate flux only. However, this benefit is compensated by an increased filtration resistance due to a thicker cake layer, so that the long-term permeate flux is independent from the feed pressure. The contribution to the conference will further include experiments with two different setups operated in submerged mode covering a variation of operating parameters, fluid characteristics, and membrane bundle design. The objectives of these studies are (i) to validate the above-mentioned theory by measuring the cake layer thickness via MRI respectively to (ii) estimate the impact of packing density on the filtration performance of a hollow-fibre bundle. While the first approach is limited to single and not-moving fibres, the latter is complementary to previous studies since both fibre movement and fibre-fibre interactions are taken into account. Hence, in conclusion, the findings out of cross-flow and submerged single fibre tests will be compared to trials with more complex configurations.

Effect of the rheology of poly(vinylidene fluoride- co-hexafluropropylene) (PVDF–HFP) dope solutions on the formation of microporous hollow fibers used as membrane contactors

The rheological properties of polymer dope solutions influence the membrane structure and performance. In the present work, the effect of shear rate on the fabrication of poly(vinylidene fluoride- co-hexafluropropylene) (PVDF–HFP) asymmetric microporous hollow fiber membranes has been studied in terms of membrane morphology, pure water flux, filtration rejection, mechanic strength and the performance of the membrane contactors made by as-spun hollow fibers for CO 2 capture. The PVDF–HFP copolymer possesses strong viscoelasticity, which is believed to be associated with the occurrence of an irregular morphology in the PVDF–HFP hollow fibers made at a high dope extrusion rate. For the first time, the viscoelastic Mach number was applied to elaborate the deformation of the inner contour of the membranes by means of characterizing the delayed die swell in the process of hollow fiber fabrication. Based on the Mach number, several batches of PVDF–HFP dope solutions with an appropriate viscosity were adopted for hollow fiber fabrication at given dope extrusion rates. The effects of the shear rate on the permeation flux and molecular weight cutoff (MWCO) of the membranes made by Batch III-2L.5T dope solution (2 wt.% LiCl and 0.5% Tween 80 as the additive) presented a V shape curve; while for the polymer dope of Batch V-2P9G (2 wt.% PVP and 9 wt.% glycerol as the additive), the effect of the shear rate on the resultant membranes showed a different pattern: increasing the shear rate resulted in smaller MWCOs, enhanced water permeation flux and higher elongation strength. These behaviors have been discussed thoroughly based on the shear-induced macromolecular chain orientation and close packing, variation of the porosity with the shear rate and shear-thinning rheological property of the dope solution under a high shear stress.

Development of negligible depletion hollow fiber–protected liquid‐phase microextraction for sensing freely dissolved triazines

A new sampling method, termed negligible depletion hollow fiber-protected liquid-phase microextraction, was developed for sensing the freely dissolved concentration (C(free)) and evaluating the availability of atrazine (ATR), desethyl atrazine (DEA), and simazine (SIM) in water. The sampling device was prepared by impregnating 1-octanol to both the pores and the lumen of a piece of polypropylene microporous hollow fiber membrane. After equilibrium and negligible depletion extraction, the 1-octanol in the lumen of the hollow fiber (10 microl) was collected for determination of triazines. Determination of C(free) and the distribution coefficient to 1-octanol (D(ow)) can be performed with this technique. A wide linear working range (1-200 microg/L) and low detection limits (0.1-1 microg/L) were obtained for triazines. Measured log D(ow) values of DEA (1.44 +/- 0.04), SIM (2.06 +/- 0.06), and ATR (2.33 +/- 0.05) agreed well with those reported in the literature. The measured D(ow) values were independent of the chemical concentration and sample pH (pH 3-10) and negligibly affected by the sample salinity (0-500 mM), suggesting that environmentally relevant pH and salinity have no significant effects on the availability of triazines. Although a slight (< or = 31%) increase of C(free) was observed, one-way analysis of variance indicated the C(free) of triazines were not significantly affected by the presence of Aldrich humic acid, Acros humic acid, and bovine albumin V (dissolved organic carbon [DOC], 0-100 mg/L). From 3 to 36% of the spiked triazines, however, were found to associate with the dissolved organic matter (DOM) in surface-water samples (DOC, 32.0-61.9 mg/L), suggesting the origin of the DOM is a key parameter in determining its association with and, thus, the availability of triazines.

Ammonium-Nitrogen Loading Rates in a Microporous Hollow Fiber Membrane Bioreactor

Ammonium-Nitrogen Loading Rates in a Microporous Hollow Fiber Membrane Bioreactor

Mathematical modeling of gas–liquid membrane contactors using random distribution of fibers

This work presents a mathematical model for gas absorption in microporous hollow fiber membrane contactors by using a random distribution of fibers. The chemical absorption of carbon dioxide into aqueous amine solutions and sulfur dioxide into water were simulated by this model. The nonlinear mathematical expressions of the component material balance for the liquid, membrane, and gas were solved simultaneously by using a numerical method. The results from the model were compared with four sets of different experimental data in the literature. In addition, the contactors were modeled based on the assumption of regular arrangement of fibers in the shell side by using Happel's free surface as well as plug flow models. The plug flow model was employed to compare the various available equations in the literature for the shell side mass transfer coefficient. The results indicate that the channeling of gas in the shell side decreases the efficiency of contactor significantly. It was found that the random distribution of fibers is a suitable method to simulate the commercial modules. The results also indicate that, the regular Happel's free surface model and the plug flow model are more suitable for handmade modules. The influence of shell side channeling on the contactor performance were investigated in different fiber packing densities, and in various gas and liquid flow rates.

Effects of Organic Phase, Fermentation Media, and Operating Conditions on Lactic Acid Extraction

Lactic acid has extensive uses in the food, pharmaceutical, cosmetic and chemical industry. Lately, its use in producing biodegradable polymeric materials (polylactate) makes the production of lactic acid from fermentation broths very important. The major part of the production cost accounts for the cost of separation from very dilute reaction media where productivity is low as a result of the inhibitory nature of lactic acid. The current method of extraction/separation is both expensive and unsustainable. Therefore, there is great scope for development of alternative technology that will offer efficiency, economic, and environmental benefits. One of the promising technologies for recovery of lactic acid from fermentation broth is reactive liquid-liquid extraction. In this paper the extraction and recovery of lactic acid based on reactive processes is examined and the performance of a hydrophobic microporous hollow-fiber membrane module (HFMM) is evaluated. First, equilibrium experiments were conducted using organic solutions consisting of Aliquat 336/trioctylamine (as a carrier) and tri-butyl phosphate (TBP)/sunflower oil (as a solvent) The values of the distribution coefficient were obtained as a function of feed pH, composition of the organic phase (ratio of carrier to solvent), and temperature (range 8-40 degrees C). The optimum extraction was obtained with the organic phase consisting of a mixture of 15 wt % tri-octylamine (TOA) and 15% Aliquat 336 and 70% solvent. The organic phase with TBP performed best but is less suitable because of its damaging properties (toxicity and environmental impact) and cost. Sunflower oil, which performed moderately, can be regarded as a better option as it has many desirable characteristics (nontoxic, environment- and operator-friendly) and it costs much less. The percentage extraction was approximately 33% at pH 6 and at room temperature (can be enhanced by operating at higher temperatures) at a feed flow rate of 15-20 L/h. These results suggest that the hollow-fiber membrane process yields good percentage extraction at the fermentation conditions and its in situ application could improve the process productivity by suppressing the inhibitory effect of lactic acid.

Mathematical modeling of the simultaneous absorption of carbon dioxide and hydrogen sulfide in a hollow fiber membrane contactor

This work presents a mathematical model for a microporous hollow fiber membrane contactor operated under non-wet or partially wetted conditions, in order to analyze the simultaneous absorption of carbon dioxide and hydrogen sulfide into an aqueous solution of diethanolamine (DEA). The diffusion-reaction processes for both acid gases were modeled based on the assumption that all reactions are reversible in the liquid bulk as well as the wetted parts of the membrane pores. A numerical scheme was developed to solve the simultaneous nonlinear mathematical expressions, and the results from the model were validated with the available experimental data in the literature. The model allows one to predict the gas phase concentration and velocity profile in the axial direction inside the shell, the liquid concentration profile in the axial and radial directions inside the fibers, and also those within the wetted parts of the pores. The results indicate that the membrane contactor can sequestrate both sour gases very effectively. Membrane wetting decreases the removal efficiency of both gases significantly in high wetting fractions. However, it mainly affects the carbon dioxide recovery in low wettings. The effects of various parameters on hydrogen sulfide selectivity were investigated, and it was found that the wetting of the membrane in low fractions increases the selectivity considerably. However, it has the opposite influence in high wetting fractions.

Steroid hormone determination in water using an environmentally friendly membrane based extraction technique

In this study, a method was developed for determination of steroid hormones (17β-estradiol, estrone, 17α-ethynylestradiol) in tap and sewage water samples from Sweden. Sample preparation and analysis were performed by a hollow-fibre microporous membrane liquid–liquid extraction (HF-MMLLE) set-up combined with gas chromatography–mass spectrometry (GC–MS). In this approach, only the organic liquid in the lumen (10 μL) of the hollow-fibre membrane was utilised for depleting extraction. Several parameters were studied, including: type of organic solvent, sample pH, salt and humic acid content. The optimised method allowed the determination of the analyte at the low ng L −1 level in tap and sewage water. A linear plot gave correlation coefficients better than 0.995 and resulted in a method limit of detection of 1.6, 3 and 10 ng L −1 for 17β-estradiol, estrone, and 17α-ethynylestradiol, respectively, in sewage water. Enrichment factors were over 1400 after derivatisation. The repeatabilities at 50 and 600 ng L −1 were better than 10% and 6%, respectively.

Effect of additives on the fabrication of poly(vinylidene fluoride- co-hexafluropropylene) (PVDF-HFP) asymmetric microporous hollow fiber membranes

The effects of two typical additives, lithium chloride (LiCl) and glycerol, on the fabrication of poly(vinylidene fluoride- co-hexafluropropylene) (PVDF-HFP) asymmetric microporous hollow fiber membranes were investigated in terms of membrane morphology, structure, permeation performance, hydrophobicity and mechanical property. The addition of the additives into the dope solution altered the morphology and structure of the resultant membranes, which was believed to be associated with the change of the thermodynamic and kinetic properties of the system in the phase inversion process. The membranes with improved pure water permeability (PWP) from 6.908 × 10 −5 (7) to 4.835 × 10 −4 (49), 3.256 × 10 −4 (33) and 5.003 × 10 −4 L/h m 2 Pa (51 L/h m 2 atm) were obtained when 2 wt.% LiCl, 4 wt.% LiCl and 10 wt.% glycerol was used as the additive, respectively. Among these, the membrane made from the dope containing 4 wt.% LiCl possessed the highest retention capability of 40 kDa molecular weight cut-off (MWCO). The LiCl or glycerol addition into the polymer dope also made the membranes exhibit a narrow pore size distribution. Moreover, the membrane hydrophobicity was affected less by LiCl and glycerol than by poly(vinyl pyrrolidone) (PVP). The addition of 4 wt.% LiCl into the dope could form the membrane with four times stronger strain strength than the poly(vinylidene fluoride) (PVDF) commercial membrane while keeping similar rigidity.