Composite Hollow Fiber Nanofiltration Membranes Research Articles

High performance composite hollow fiber nanofiltration membrane fabricated via the synergistic effect of co-solvent assisted interfacial polymerization and macrocyclic polyamine incorporation

The necessity for high-performance thin film composite (TFC) nanofiltration (NF) membranes for drinking water and wastewater treatment is becoming increasingly apparent in the face of the global water crisis. In this work, co-solvent (acetone) assisted interfacial polymerization (CAIP) and incorporating macrocyclic polyamine (Cyclen) as an aqueous co-monomer were employed to fabricate hollow fiber (HF) NF membrane and to enhance the permeability and the selectivity, respectively, thereby overcoming the inherent trade-off effect. The effects of Cyclen and acetone on the separation performance were comprehensively investigated, and the interfacial polymerization conditions were optimized. The optimal HF NF membrane exhibits a 68.6 % increment in water permeance relative to the baseline membrane while without sacrificing the Na2SO4 rejection which is as high as 99.2 %. In particular, it exhibits a superior high pure water permeability of 222.5 L m−2 h−1 MPa−1, ranking among the highest observed for HF NF membranes in the existing literature. Moreover, it exhibits excellent acid resistance as well as fouling resistance. This research paves a novel approach for developing high-performance HF NF membranes for water and wastewater treatment.

Construction of a novel poly(amide-ester) thin film composite hollow fiber nanofiltration membrane with high water permeance

Highly permeable hollow fiber (HF) nanofiltration (NF) membrane is strongly desired since it could achieve efficient desalination with much less energy consumption. In this study, we used 4,4′,4′′-trihydroxytriphenylmethane (TP) as an aqueous co-monomer with piperazine (PIP) to react with trimesoyl chloride (TMC) to prepare a new internally pressurized poly(amide-ester) HF NF membrane. With the incorporation of TP molecules, the synthesized poly(amide-ester) separation layer achieved larger pore size and better hydrophilicity, giving the HF NF membrane excellent water permeance. Under optimum conditions, the HF NF membrane has a water permeance of 151 L m−2 h−1 MPa−1, which is 50 % higher than that of the control HF NF membrane, while maintaining a Na2SO4 rejection of 97.5 %. Moreover, it displays excellent desalination performance towards heavy metal salt solutions and high salinity solutions. It also maintains excellent desalination performance during a long-time filtration experiment, which indicates its good durability performance. In summary, this new poly(amide-ester) HF NF membrane shows good promise for the treatment of heavy metal and high-salinity wastewaters.

Construction of a high-performance hollow fiber composite NF membrane via the simultaneous modification of substrate and selective layer

Hollow fiber composite (HFC) nanofiltration (NF) membrane demonstrates significant commercial potential profiting from its self-supporting characteristic, high packing density and strong fouling resistance. In this work, a high-performance HFC NF membrane was successfully developed through simultaneous modification of the substrate via alkaline hydrolysis and incorporation of iopamidol (IPD) into the selective layer. Alkaline hydrolysis enhanced the hydrophilicity of the polyacrylonitrile (PAN) substrate by converting –CN groups into –COOH, thereby sharply improving the success rate of HFC NF membrane fabrication. The addition of IPD into piperazine (PIP) solution effectively increased the water permeability of the HFC NF membrane without compromising its salt rejection. Specifically, the optimized membrane sample denoted as NF-0.15P + 0.5I with 0.5 w/v% IPD added demonstrated a 44 % increase in PWP from 21.8 L·m−2·h−1·bar−1 to 31.5 L·m−2·h−1·bar−1, while maintaining a Na2SO4 rejection over 96.8 %. This improvement can be attributed to the decreased selective layer thickness and reduced MWCO. Furthermore, the membrane exhibited exceptional dye/salt separation performance. This work represents a novel approach leading to the development of a HFC NF membrane suitable for dye/salt separation.

Open and dense hollow fiber nanofiltration membranes through a streamlined polyelectrolyte-based spinning process

Polyelectrolyte composite hollow fiber membranes show a high potential to become applied in industrial nanofiltration applications such as water purification or downstream processing in several industries. This material platform allows multiple routes to achieve tailored selectivities and high permeances. Hollow fiber membranes promise a higher process efficiency due to higher packing densities and their backwash stability. However, the fabrication of composite polyelectrolyte hollow fiber nanofiltration membranes is more challenging compared to state of the art spiral wound modules. While the Layer-by-Layer deposition has proven versatile opportunities and is recently entering the commercial market, the multi-step post-treatment is elaborate. In this work, we streamline the fabrication of polyelectrolyte composite hollow fiber membranes. We extend our recently presented ”chemistry-in-a-spinneret” approach with a membrane modification in a subsequent coating bath. The additional modification can be incorporated in the composite hollow fiber membrane manufacturing process without additional process steps. Sulfonated polyethersulfone as a polyanionic additive is used in the polymer solution which complexates with the polycations polyethylenimine (PEI) or poly(diallyldimethylammonium chloride (PDADMAC) in the bore fluid during fiber spinning. The extruded fibers have a positively charged lumen surface which allows a subsequent modification with the polyanion poly(sodium 4-styrenesulfonate) (PSS) in the coating bath. The spun fibers reveal with 16-4 LMH/bar pure water permeance (PWP) and 2000-1100 Dalton (Da) molecular weight cut-off (MWCO) open nanofiltration characteristics, while the PEI+PSS modified fibers show dense nanofiltration characteristics (0.6 LMH/bar PWP and 360 Da MWCO). The fibers are backwash stable and the PDADMAC and PDADMAC+PSS fibers show a significantly higher sodium hypochlorite (NaOCl) stability compared to the PEI and PEI+PSS fibers. This new technique creates composite hollow fiber nanofiltration membranes with a polyelectrolyte bilayer without multi-step post-treatment. Therefore, it provides a promising alternative to the Layer-by-Layer post-modification, where two coating steps and one water washing post-treatment step are required to create a polyelectrolyte bilayer on a porous hollow fiber membrane support. • Composite hollow fiber nanofiltration membranes without multi-step post-treatment. • The chemistry in a spinneret technique is extended with a polyanion coating step. • Backwash stable hollow fibers feature open or dense NF characteristics. • PDADMAC and PDADMAC+PSS show higher NaOCl stability compared to PEI and PEI+PSS. • Fibers with open NF characteristics are competitive with commercial nanofiltration membranes.

Designing scalable dual-layer composite hollow fiber nanofiltration membranes with fully cross-linked ultrathin functional layer

The treatment of industrial wastewater containing complex foulants demands high efficiency yet cost-effective separation process. The composite hollow fiber nanofiltration membranes suffer from tedious fabrication procedures, impeding the large volume fabrication and application. Herein, we reveal a very simplified designing strategy by polyelectrolyte modification of the co-extruded polyimide/polyethersulphone dual-layer hollow fibers with hierarchical structure and chemistry. The active layer's thickness of the dual-layer hollow fiber substrate is only 800 nm, the thinnest in literature. Compared to integral active single layer hollow fiber, the ultrathin active layer not only leads to over 4 times increase in mechanical flexibility and tenfold reduction in material cost but also enables fully chemical transition from imide to cross-linked polyamide, minimizing the intrinsic hydrolysis tendency of active material. The optimized membranes with a well-defined pore radius of 0.23 nm have 93–95% rejection to Mg2+ and Ca2+ and PWP of 9.1 LMH/bar. Moreover, the composite membranes exhibit backwash ability and stability in the heated feed solutions, which meets the demand for direct treatment of industrial effluents. This work paves the way for the large volume fabrication and application of hollow fiber nanofiltration membranes for treating municipal water, industrial wastewater, and other applications.

Ionic and pH responsive thin film composite hollow fiber nanofiltration membrane for molecular separation

Ionic and pH responsive thin film composite (TFC) membrane is prepared by interfacial polymerization of lysine and trimesoyl chloride on the out surface of poly (m-phenylene isophthalamide) hollow fiber membrane. Hydrophilicity and strong negative charge of the TFC membrane are obtained by introducing a large amount of carboxylic groups in the cross-linked polyamide network, endorsing the ionic and pH response of the TFC membrane in terms of flux and rejection. The TFC membrane shows almost 100% rejection for Eriochrome black T, with a flux of 35.8 L/m2h (0.2 MPa) at low pH and salt concentration. However, the rejection decreases to 95.8%, and the flux increases more than three times at high pH and salt concentration due to the shift of the interaction in the polyamide network from hydrogen bonding to static-electric repulsion. The responsive TFC membrane also shows great performance in separation of dye-salt mixture and dye mixture.

Graphene oxide interlayered thin-film nanocomposite hollow fiber nanofiltration membranes with enhanced aqueous electrolyte separation performance

In this study, a kind of thin-film nanocomposite (TFN) hollow fiber nanofiltration (NF) membranes was fabricated via incorporating graphene oxide (GO) interlayer using the interfacial polymerization (IP) reaction between piperazine (PIP) and trimesoyl chloride (TMC). The surface morphology and cross-sectional structure of the fabricated TFN hollow fiber NF membrane were extensively investigated. The effects of the PIP concentration, species of the aqueous additives, and the GO loading on the structure and performance of the hollow fiber NF membrane were also investigated in detail and the optimal preparation conditions were achieved. Fourier transform infrared spectroscopy (FTIR) confirmed the successful introduction of the GO interlayer into the composite hollow fiber NF membrane. Moreover, the incorporation of GO interlayer helped to reduce the skin thickness of the composite hollow fiber NF membrane remarkably, and thus helped to increase greatly the water permeance while maintaining a high salt rejection. Under an optimal GO loading of 20.0 mg m−2, the TFN hollow fiber NF membrane achieved a water permeance of 80 L m−2 h−1 MPa−1 and a Na2SO4 rejection of 96.1% for 2000 mg L−1 aqueous Na2SO4 solution, much higher than the interlayer-free thin-film composite (TFC) membrane. Meanwhile, the TFN hollow fiber NF membrane showed an excellent selectivity of Na2SO4 over NaCl, as well as good fouling resistance and long-term stability, demonstrating the vast potential in application for the selective separation of monovalent salt and divalent salt.

Preparation of internally pressurized polyamide thin-film composite hollow fiber nanofiltration membrane with high ions selectivity by a facile coating method

Internally pressurized polyamide thin-film composite (TFC) hollow fiber nanofiltration (NF) membrane with high ions selectivity was prepared by a facile coating method including the dip-coating of the aqueous phase and reverse direction coating of organic phase. Surface composition and morphologies of the prepared NF membrane were characterized by ATR-FTIR, FESEM and AFM. Membrane hydrophilicity was evaluated by Water Contact Angle (WCA) measurements. The dip-coating time of the aqueous phase and reverse direction coating time of organic phase were optimized. The results indicated that the ultra-thin functional layer was successfully formed on the lumen side of hollow fiber PSF substrate membrane. Under the optimized conditions including the dip-coating time of 20 min and reverse direction coating time of 60 s, the prepared TFC hollow fiber NF membrane exhibited an excellent separation performance with the 99.5 % rejection of MgSO4 (1 g/L) and pure water flux of 43.3 L/m2h at 0.7 MPa. The prepared NF membrane showed a high selectivity with the separation factor of MgSO4/NaCl) of 7.8. NF membrane exhibited a uniform separation performance along fiber length compared with the traditional single direction coating.

Preparation and characterization of a novel positively charged composite hollow fiber nanofiltration membrane based on chitosan lactate.

A positively charged composite hollow fiber nanofiltration (NF) membrane was prepared via interfacial polymerization (IP) between chitosan lactate (CL) and trimesoyl chloride (TMC) on a polyether sulfone (PES) hollow fiber ultrafiltration (UF) membrane. The chemical structure and the morphologies of the resultant NF membranes were characterized with attenuated total reflectance-infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM). The rejection of NF membrane for different inorganic salt aqueous solutions followed the order: MgCl2 > ZnCl2 > MgSO4 > NaCl > Na2SO4. It suggested that this novel kind of composite hollow fiber NF membrane is positively charged. The molecular weight cut-off (MWCO) was obtained through the rejection of polyethylene glycol (PEG) solutions with different molecular weights (Mw). The effect of monomer concentrations, the interfacial polymerization time, and the curing temperature, were investigated, respectively. The rejection and the permeate flux of the resultant composite hollow fiber CL membrane fabricated under the optimal conditions towards a MgCl2 solution of 1000 ppm were 95.1% and 10.3 L m−2 h−1, respectively, at 0.4 MPa and 25 °C. Moreover, the effects of operation conditions on the rejection performance of the composite hollow fiber NF membrane were investigated. It suggested that this novel kind of hollow fiber composite nanofiltration membrane based on CL have excellent stability in rejection performances to salt solutions.

Typical pharmaceutical molecule removal behavior from water by positively and negatively charged composite hollow fiber nanofiltration membranes.

The rejection behaviors of two different charged composite hollow fiber nanofiltration (NF) membranes for six pharmaceutical molecules, primidone, carbamazepine, sulfamethoxazole, atenolol, sulfadimidine and norfloxacin, were characterized in this study. The saturation adsorption behaviors of the different pharmaceutical molecules on each membrane surface were studied and found to be related to the molecular weight, charge and hydrophilicity of the pharmaceutical molecules. After the pharmaceutical molecules reached adsorption equilibrium, the rejection rates of different NF membranes were characterized. The rejection rates of primidone, carbamazepine, sulfamethoxazole, atenolol, sulfadimidine and norfloxacin by the PEI-NF membrane were 85.6%, 91.8%, 79.9%, 98.1%, 93.3%, and 97.1%, respectively. Meanwhile, the rejection rates of the pharmaceutical molecules by the PIP-NF membrane were 82.2%, 85.4%, 91.5%, 79.1%, 87% and 93.3%, respectively. The influence of feed concentration, operation pressure, temperature, pH and ionic strength on the rejection behaviors of the different charged NF membranes were also studied.

Removal of lead ions using polyamide hollow fiber composite nanofiltration membrane containing crown ether

Removal of lead ions using polyamide hollow fiber composite nanofiltration membrane containing crown ether

Polyamide/PVC based composite hollow fiber nanofiltration membranes: Effect of substrate on properties and performance

Thin film composite nanofiltration membranes were successfully prepared via interfacial polymerization between piperazine and trimesoyl chloride on poly(vinyl chloride) hollow fiber substrates with different properties. Both the polyamide layer and underlying substrate were characterized with respect to chemical and morphological structures. The effects of substrate properties on the characteristics of the prepared nanofiltration membranes were investigated. It is found from the results that the differences in substrate properties, mainly the membrane pore size and porosity had significant contributions to the changes in the thickness and cross-linking degree of poly(piperazine-amide) layer during the interfacial polymerization process, leading to the varied performance of the prepared nanofiltration membranes in terms of MgSO4 rejection and permeate flux. The nanofiltration membrane prepared from the substrate with medium pore size and porosity exhibited a relatively higher permeate flux as well as a superior rejection for MgSO4, which showed typical rejection orders for different salts as well as good stabilities after backwash treatment and a long-term filtration process. These results indicate that the prepared poly(vinyl chloride) nanofiltration hollow fiber membranes could be applied to the desalination or water softening process.

High-flux composite hollow fiber nanofiltration membranes fabricated through layer-by-layer deposition of oppositely charged crosslinked polyelectrolytes for dye removal

Composite hollow fiber nanofiltration membranes with an active skin layer comprising only one polyelectrolyte bilayer were prepared through layer-by-layer deposition of oppositely charged polyelectrolytes of sodium carboxymethyl cellulose (CMCNa) and polyethylenimine (PEI) on polypropylene hollow fiber substrate, with glutaraldehyde crosslinking between each deposition. Membrane performance was optimized by varying the contents of CMCNa and PEI of the deposition solutions and the obtained membranes were characterized in terms of physico-chemical characteristics and permeation properties. Experiments revealed that the obtained membrane was positively charged and exhibited a salt rejection order of MgCl2>CaCl2>KCl>NaCl>MgSO4>Na2SO4 at neutral pH. The optimized membrane had a molecular weight cut-off of about 730g/mol and possessed a pure water permeability of 14.2l/m2hbar, MgCl2 rejection of 93.2% and NaCl rejection of 36.2% in filtration of 500mg/l salt aqueous solution at 3.0bar. The desired membrane could also effectively remove organic dyes from aqueous solution, showing retentions of 99.8%, 99.6% and 99.4% to Brilliant green, Victoria blue B and Congo red, respectively, under the trans-membrane pressure of 3.0bar. These promising results demonstrate that the technique developed in this study is potentially applicable for preparing high-flux nanofiltration membrane for dye removal and partial desalination.

Fabrication of a high-flux thin film composite hollow fiber nanofiltration membrane for wastewater treatment

A high-flux thin film composite (TFC) hollow fiber nanofiltration (NF) membrane was fabricated using a barrier layer of polypiperazine amide synthesized via interfacial polymerization (IP) on a previously prepared dual-layer (PES/PVDF) hollow fiber substrate, which was synthesized via the two-step TIPS/NIPS method. The permeability of the TFC membrane was smaller by an order of magnitude than that of the substrate, which was due to the formation of a thick barrier layer. The structure of the barrier layer was controlled via the addition of cyclic ethers (dioxane, oxolane and trioxane). By increasing the polarity of cyclic ethers, the thickness of the barrier layer and the dense layer was reduced due to the piperazine concentration in the organic phase. Comparing with oxolane and trioxane, the addition of dioxane resulted in a narrower pore size as that of the conventional IP process, which was ascribed to the narrow IP reaction zone via the immiscibility of interface. With the addition of dioxane up to 2wt%, the barrier layer became thinner, the pure water flux of the resultant membrane was improved and the dextran rejection was maintained. The novel hollow fiber NF membrane has a permeability of 16.6Lm−2h−1bar−1, a MWCO of 330Da and a tensile strength of 10.3MPa. This membrane had a higher rejection of total organic carbon and a lower rejection of total dissolved solids of the secondary effluent from a petrochemical industry plant, which proves the potential of this membrane in municipal, agricultural and industrial wastewater treatment.

Stabilization of composite hollow fiber nanofiltration membranes with a sulfonated poly(ether ether ketone) coating

Composite hollow fiber nanofiltration membrane coated with a thin layer of sulfonated poly(ether ether ketone) (SPEEK) can separate monovalent ions from multivalent ions with a low energy demand. It has found applications in desalination of glyphosate wastewater and removal of arsenic from drinking water. Before large scale application of such membranes, one of the main issues is the long time performance stability. This paper reports, for the first time, systematic investigations on the origins of the instability of the SPEEK composite membrane in aqueous phase. Membrane preparation parameters, the coating polymer concentration, the coating time, and the post-treatment temperature were correlated to the membrane stability. A reptation mechanism was proposed to explain the rejection decline and flux increase with time, based on swelling and dissolution of SPEEK. To reduce the swelling and loss of SPEEK, a PVA/SPEEK blend was used as the coating layer, which after cross-linking by glutaraldehyde, yielded a NF membrane with constant rejection during 2000h of operation.

Preparation and performance of SPPES/PPES hollow fiber composite nanofiltration membrane with high temperature resistance

Sulfonated poly(phthalazinone ether sulfone)/poly(phthalazinone ether sulfone) (SPPES/PPES) hollow fiber composite nanofiltration membrane was prepared by coating a SPPES layer on top of the PPES hollow fibers via the dip-coating method. Effects of the composition of coating solution and preparation conditions as well as the operating conditions on the performance of the SPPES/PPES composite membrane (CM) were investigated. It was found that an optimum rejection ratio of CM1 for 1000mg/L Na2SO4 solution was 93.6%, and the pure water flux was 8.7L/(m2·h) under an operating pressure of 0.35MPa at 20°C. The flux of CM1 can be up to 58L/(m2·h) with the operating temperature increased from 20°C to 90°C, while the rejection for 1000mg/L Na2SO4 solution only had a slight change at the pressure of 1.0MPa. Furthermore, a short time stability measurement for about 200h proved that the SPPES/PPES composite membrane had much better performance at a high operating temperature. Finally, a back-washing method was used to clean the pollution substances after the stability measurement, and performance of the composite membrane almost reached the initial value with the hydraulic washing time of 20min at 50°C under the pressure of 0.3MPa.

Preparation and characterization of high‐selectivity hollow fiber composite nanofiltration membrane by two‐way coating technique

ABSTRACTA novel coating technique, named as two‐way coating (TWC), was explored to prepare hollow fiber composite (HFC) nanofiltration (NF) membrane through interfacial polymerization from piperazine (PIP) and trimesoyl chloride (TMC) on the lumen side of hollow fiber polysulfone ultrafiltration membrane with an effective membrane area of 0.4 m2. The optimum preparation conditions were systematically investigated and obtained as follows: PIP 0.023 mol/L, TMC 0.0057 mol/L, air blowing rate 2.7 m/s for 30 min after aqueous coating, aqueous coating pressure 0.1 MPa, organic solution flowing rate 0.32 m/s, and heat treating time 3 min. The resultant HFC membrane showed a high selectivity of divalent ion and monovalent ion. Salt rejections of MgSO4 and NaCl were 98.13 and 18.6% with the permeate flux of 32.6 and 40.2 L m−2 h−1 at 0.7 MPa, respectively. Field emission scanning electron microscopy images indicated that composite membrane prepared by TWC technique had a uniform active layer from the upper end to the bottom of the hollow fiber. And the salt rejection and permeate flux showed almost no difference between different membrane sections. Stability results suggested that good reproducibility could be obtained by TWC technique for the preparation of high‐performance HFC NF membrane. The resultant NF membrane showed a high removal rate of chemical oxygen demand and chroma of landfill leachate which were approximately 100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41187.

Positively charged thin-film composite hollow fiber nanofiltration membrane for the removal of cationic dyes through submerged filtration

Positively charged thin-film composite hollow fiber nanofiltration membranes were developed by the dip-coating method using polypropylene hollow fiber microfiltration membrane as support, polyvinyl alcohol (PVA) and polyquaternium-10 (the reaction product of hydroxyethyl cellulose with a trimethylammonium substituted epoxide, PQ-10) as coating materials, and glutaraldehyde as cross-linking agent. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), measurements of streaming potential and contact angle were employed to characterize the obtained membranes. The permeation properties were estimated through pressurized cross-flow permeation tests and the dye removal performance were evaluated through submerged filtration tests using cationic dye aqueous solutions. It was found that the salt rejection order of the membrane was CaCl2>MgCl2>NaCl>MgSO4>Na2SO4 at neutral pH. The desired membrane with a molecular weight cut-off of about 650Da had a pure water flux of 25.7l/m2h and a rejection of 92.8% to 500mg/l CaCl2 aqueous solution at 3.0bar. The membrane could effectively remove cationic dyes from aqueous solution with good long-term performance stability through submerged filtration. The observed rejections to Brilliant green, Victoria blue B and Crystal violet were 99.8, 99.8 and 99.2%, respectively, under the trans-membrane pressure of 0.7bar.

Composite hollow fiber nanofiltration membranes for recovery of glyphosate from saline wastewater

A high performance versatile composite hollow fiber nanofiltration (NF) membrane is reported for the separation of glyphosate from saline waste streams. Preparation of SPEEK based on an amorphous poly (ether ether ketone, PEEK) was investigated. The membrane was prepared by coating sulfonated polyether ether ketone (SPEEK) onto a polyethersulfone (PES) ultrafiltration (UF) hollow fiber membrane. The composite membrane was characterized by water permeability, scanning electron microscopy, and rejection toward sodium sulfate (Na2SO4), sodium chloride (NaCl), and calcium chloride (CaCl2). About 90% rejection toward sulfate anions and only 10% rejection for calcium cations were obtained. A water permeability around 10–13 LMHBar and 90% rejection for polyethylene glycol (PEG) with a molecular weight of 4000–6000 Da were observed. In the separation of glyphosate from saline wastewater, the membrane rejected less than 20% of NaCl and higher than 90% of glyphosate at an operating pressure of 5 bars and pH = 11.0. An economic analysis indicated that the cost for recovery of glyphosate was comparably low to the value gained by an increase in the productivity. The results may lead to a new promising low energy solution for the environmental problem faced by the herbicide industry.

Preparation of polysulfone–polyamide thin film composite hollow fiber nanofiltration membranes and their performance in the treatment of aqueous dye solutions

Thin film composite hollow fiber nanofiltration membranes containing poly(m-phenylene-trimesamide) active layer on polysulfone ultrafiltration membrane were prepared by in situ interfacial polymerization between m-phenylenediamine and trimesoyl chloride under different conditions. The nanofiltration membranes exhibited molecular weight cut-off values in the range of 490 to 730g/mole. They showed the rejections in the range of 60–97% for reactive black-5 and rhodamine-B with water flux of 10–35mL/m2h at 25psi for feed solutions containing 400–2000ppm dye. The flux was decreased slightly while the rejection was remained almost the same upon increasing the dye concentration from 400ppm to 2500ppm in feed. The dye rejection and flux of the membranes were found to be reduced by 2–5% when tested with feed solutions containing a mixture of dye and NaCl (up to 10,000ppm). This may be attributed to either the decrease in Donnan's exclusion effect or change in membrane pore structure by salting out or by pore swelling effect. The membranes were characterized by SEM and AFM for surface morphology. The surface roughness was found to be in the range of 20 to 40nm, as observed by AFM, depending upon polyamide preparation conditions.