Performance Of Ultrafiltration Membranes Research Articles

Enhanced water permeance and antifouling performance of gravity-driven ultrafiltration membrane with in-situ formed rigid pore structure

Gravity-driven membrane (GDM) has emerged as a low-energy technique of water treatment. However, low water flux limits the application of GDM, due to membrane fouling and pore deformation. For the first time, gravity-driven Polyvinylidene Fluoride (PVDF) ultrafiltration membrane with rigid pore structure was fabricated by in-situ formed four-arms star polystyrene (FAS-PS) microspheres in an easy one-step phase separation process. The self-assembly of FAS-PS molecular chains caused PVDF chains to shrink, leading to the generation of more porous structure. The tightening effects of in-situ rigid FAS-PS microspheres enhanced the anti-deformation capability of membrane. As a result, water flux decline of [email protected] membrane was significantly inhibited during GDM filtration process. The stable water flux of [email protected] membrane was approximately 5 times than that of the control PVDF membrane. Furthermore, the anti-deformation character of [email protected] membrane was beneficial to reduce membrane fouling, which was demonstrated by the reduced amount of bovine serum albumin (BSA) clogged in rigid pore structure. These enhanced performances were attributed to the simultaneous reduction of plastic and elastic deformation of membrane pore structure in GDM process. This study provides a completely novel strategy to improve the water flux and anti-fouling ability of GDM.

A Metal-organic composite ultrafiltration membrane synthesized via Quadratic phase inversion

• Stainless steel wire mesh as substrate was used to fabricate composite UF membrane. • A novel strategy denoted as“Quadratic Phase Inversion (QPI)” was proposed. • Composite UF membrane showed high pure water flux and desirable BSA rejection. • Composite UF membrane prepared with “QPI” showed superior running stability. According to the Pore-flow model describing the mass transfer process of Ultrafiltration (UF) membranes, the thickness of the separation layer directly determines the separation performance of an UF membrane: pure water flux (PWF) and foulant rejection. However, the flexibility and limited supporting capacity of the conventional supporting layer (non-woven fabric) limits the further reduction of the separation layer thickness. In this study, stainless steel wire mesh (SSWM) was employed as the supporting layer to fabricate a metal/polymer composite UF membrane via a novel strategy denoted as “Quadratic Phase Inversion (QPI)”, in which the SSWM was firstly modified with a casting solution with low PVDF concentration, and then another PVDF selective layer was constructed on the modified substrate with the conventional phase inversion method. Orthogonal experiment was conducted to optimize the fabrication parameters. A series of characterization was adopted to analyze the performance and structural evolution. The results demonstrate that a composite UF membrane with ultrathin PVDF selective layer could be fabricated on the PVDF modified SSWM. The optimized sample was obtained with the SSWM modification reagent of 3 wt% PVDF, the casting solution of 20 wt% PVDF, the casting thickness of 75 μm, and NMP as solvent, which had a MWCO of 149 kDa and mean pore diameter of 7.2 nm. Meanwhile, it presented a high PWF around 448.8 L m −2 h −1 bar −1 , desirable BSA rejection about 96.3% and good operation stability. The outcome of this research is expected to provide a valuable route for promoting the separation performance of UF membranes.

Separation of single and mixed anionic dyes in saline solutions using uncharged polyacrylonitrile-tris(hydroxymethyl)aminomethane (PAN-Tris) ultrafiltration membrane: Performance and mechanism

Separation of single or mixed dyes in saline solutions can recover valuable chemicals from dye-containing wastewater. Application of ultrafiltration (UF) in this area is limited by the performance of traditional UF membranes and remains a challenge to achieve high efficacy. Herein, three uncharged polyacrylonitrile-tris(hydroxymethyl)aminomethane (PAN-Tris) UF membranes were adopted for anionic dye separation in saline solutions. These membranes were prepared via in situ modification and characterized by XPS, 1H NMR spectroscopy, contact angle, permeation, mechanical properties, etc. Congo red (CR), methyl blue (MB), and methyl orange (MO) were chosen as model dyes with different sizes and valences. The as-prepared PAN-Tris membranes possessed mean pore sizes ranging from 8.14 to 10.98 nm, but with strong negative zeta potential ranging from −12 to −43 mV at pH 7. Thus, they rejected above 98% CR (with large molecular size) and MB (with high valence), and fractionated the mixtures of CR or MB with MO (with monovalence) in water solutions. The maximum flux of a dye solution reached about 85 L⋅m−2⋅h−1 at 1 bar. Subsequently, the influences of operating pressure, dye concentration, pH value, salt type (NaCl, Na2SO4, MgCl2, or MgSO4) and salt concentration (1000, 5000, or 10000 ppm) on the dye separation property of the membranes were investigated. The results showed that dye rejection behavior depends on the molecular size and valence of dye, as well as membrane property. Thereafter, the electric double layer (EDL) model and the static permeation analysis were combined to investigate the separation mechanism through the changes of the electrostatic effects and effective pore sizes of the membranes in saline solutions. Guided by the revealed mechanism, the MB/CR mixture was successfully separated by using a NaCl solution (≥5000 ppm) for the first time. Overall, this study not only demonstrates that novel UF membranes hold promise for highly effective treatments of dye-containing wastewater, and but also provides an insightful understanding of the dye rejection mechanism that can guide the rational design of UF membranes.

Studying the performance of various polymeric ultrafiltration membranes in dye removal

Studying the performance of various polymeric ultrafiltration membranes in dye removal

Performance of mixed matrix ultrafiltration membrane for textile wastewater treatment

Textile wastewater contains high level of chemical oxygen demand (COD) and color concentration, and the release of this effluent can adversely affect ecosystem and water quality. Conventional ultrafiltration (UF) membrane incapable to treat small size pollutants (such as dyes and multivalent ions) from the wastewater. Previously, we had successfully fabricated tannin-modified metal–organic frameworks (Tannin-MIL), then incorporated it in the polyethersulfone (PES) polymer matrix. The modified membrane has more hydrophilic surface than unmodified PES surface, making it more resistant and less prone to be affected by fouling. Herein, this study aimed to explore the performance of ultrafiltration mixed matrix membrane for textile wastewater treatment. The novel Tannin-MIL/PES membrane possessed excellent rejection up to ∼ 100% total suspended solid (TSS), 96.46% (COD), 97.04% (color), 97.41% (turbidity) and 89.94% total dissolved solid (TDS), with permeability up to ∼ 190 L/m2.h.bar during filtration of textile wastewater, which is 9.31 times higher compared to the unmodified PES membrane.

Enhanced Performance of PVDF Composite Ultrafiltration Membrane via Degradation of Collagen-Modified Graphene Oxide

The collagen obtained from chrome leather waste can be used to modify graphene oxide (GO) to prepare polyvinylidene fluoride (PVDF) composite ultrafiltration membranes, a process that is conducive to the recovery of leather waste, comprehensive utilization of GO and improved performance of the membrane. In this paper, collagen-modified GO (CGO) was prepared by degradation of collagen from chrome leather waste and used to prepare a PVDF composite ultrafiltration membrane. The results show that the carboxyl content of CGO and dispersion were improved. The water flux and flux recovery rate of the modified ultrafiltration membrane were improved. The bovine serum albumin (BSA) intercepted on the membrane surface was easy to clean and the antifouling performance improved. The performance of the membrane decreased when the GO content exceeded 0.75 wt%, while CGO can reach 1.0 wt% without agglomeration due to its good dispersion.

SEPARATION OF HEMICELLULOSES FROM AN INDUSTRIAL STREAM BY NANOFILTRATION AND ULTRAFILTRATION PROCESSES

The performance of nanofiltration (NF) and ultrafiltration (UF) membranes was studied for separating hemicelluloses from a highly alkaline industrial stream, containing 17-18 wt% sodium hydroxide, resulting from the viscose process. Initially, screening experiments were performed to select suitable membranes, which were then investigated on a pilot scale spiral module. Screening experiments showed that the UF membrane, with a nominal molecular weight cut-off (MWCO) value of 3 kDa, and the NF one, with a nominal MWCO value of 0.5 kDa, showed a similar range of filtration performance and a flux of 4.2 L/m2.h. Further, a retention efficiency of 50% was observed for the 5 kDa and the 10 kDa membranes, indicating absence of any significant proportion of hemicelluloses in this range of molecular weights. The effects of process conditions were studied to understand their correlation with membrane performance with respect to hemicelluloses retention and permeate flux. UF membranes were found to be more prone to performance deterioration over time and with the number of cycles of usage during the pilot scale study, whereas the NF membrane showed consistent performance. It was seen that feed dilution can improve the membrane performance with respect to sodium hydroxide recovery. Significant reduction in feed viscosity with dilution resulted in a 50% increase in flux after normalizing for concentration.

Fabrication of ZIF-67@PVDF ultrafiltration membrane with improved antifouling and separation performance for dye wastewater treatment via sulfate radical enhancement

• PVDF ultrafiltration membranes were prepared using pristine ZIF-67 nanoparticles. • ZIF-67 were exhibited excellent catalytic activity in the PVDF membrane. • Utilizing ROS generated from PMS-activated ZIF-67@PVDF to enhance dye removal. • The flux/ FRR of the ZIF-67@PVDF-1.0 membrane were 4.25/2 times that of PVDF. • On-line cleaning achieved an average AO7 maximum removal of 98.9% within pH = 11.0. Efficient separation and excellent antifouling performance of ultrafiltration (UF) membrane are highly desirable for sustainable wastewater treatment. This work reports a novel ZIF-67-imbedded PVDF (ZIF-67@PVDF) mixed-matrix UF membrane fabricated by nonsolvent-induced phase separation (NIPS) technique to reinforce efficient removal of dye wastewater via sulfate radical enhancement. The imbedded ZIF-67 well-dispersed within the membrane improved the membrane pore structure and benefited peroxymonosulfate (PMS) activation to generate sulfate radical that were confirmed by Electron spin resonance (ESR) spectroscopy. As a synergistic effect of pore structure and sulfate radical generation, the separation, antifouling and catalytic performance of the ZIF-67@PVDF membranes were greatly enhanced over a wide pH range. Even at a high pH of 11, the PMS on-line cleaning assisted ZIF-67@PVDF-1.0 membrane achieved high dye removal efficiency for orange Ⅱ (AO7, 97.3%), Methylene blue (98.2%), Rhodamine B (90.5%). The ZIF-67@PVDF membrane also showed good reusability and stability. This work demonstrates great potential of using self-cleaning UF membranes to treat dye wastewater.

Effects of GO-PEG on the performance and structure of PVC ultrafiltration membranes

In this work, neat and nanocomposite polyvinyl chloride (PVC) membranes with various contents of graphene oxide-poly ethylene glycol (GO-PEG) nanosheets were fabricated via non-solvent phase separation (NIPS) method. The results of field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses approved the successful synthesis of GO-PEG nanosheets. Fabricated PVC/GO-PEG membranes were characterized by atomic force microscopy (AFM), water content, FESEM, contact angle, porosity, pure water flux (PWF), abrasion resistance and tensile strength tests. FESEM images illustrated the increased porosity of membranes after embedding of GO-PEG. The results showed that by addition of nanosheets, abrasion resistance of membranes enhanced as a reason of good mechanical properties of GO. Moreover, PWF was improved from 50 L/m2 h in neat PVC to around 211 L/m2 h in 0.15 wt.% PVC/GO-PEG membrane. Finally, MBR filtration test was utilized for 360 min to evaluate membranesʼ performance. In this case, Reversible Fouling Ratio (RFR) increased (from 9% in neat PVC membrane to 33% in PVC/GO-PEG 0.15 wt.% membrane) and Irreversible Fouling Ratio (IFR) decreased (from 51% in neat PVC to 37% in PVC/GO-PEG 0.15 wt.% membrane) by addition of GO-PEG nanosheets. The improved antifouling properties of PVC/GO-PEG membranes can be attributed not only to the hydrophilicity effect of GO-PEG nanosheets which prevents the foulants from attaching to membranes surface but also to the increased flux of PVC/GO-PEG membranes.

Ultrafiltration Membrane Performance Fitted In Dead-End Stirred Filtration Cell (DESFC) In Concentrating Shank Gelatin

Performance of Ultrafiltration (UF) Membrane fitted in dead-end stirred filtration cell (DESFC) as a membrane-based unit operation is an essential factor in concentrating shank gelatin to produce concentrated gelatin as a food additive. This study aimed to determine the optimum performance and to evaluate the feasibility of commercial UF flat-sheet membranes (1,000, 20,000 and 100,000 MWCO) equipped in DESFC. The experiment was conducted at gelatin and water ratio of 1:0, 1:2, 1:4 and 1:6 in a laboratory scale with stirring speed of 400 rpm and trans-membrane pressure (TMP) of 40 psia for 30 minutes and resulted in retentate (concentrate) and permeate of shank gelatin. The results showed that larger pores size of the membrane and high ratio of gelatin and water increased both permeate flux and rejection. Based on permeate flux and dissolved protein, the optimum separation condition was achieved using UF membranes of 100,000 MWCO and a gelatin and water ratio of 1:6. This optimum condition resulted in permeate flux of 0.0215 mL/cm2.min. and dissolved protein Robs of 100%.

Simultaneously enhanced permeability and anti-fouling performance of polyethersulfone ultrafiltration membranes by structural control and mixed carbon quantum dots

Assisted with a direct current (DC) electric field membrane forming device, the Polyethersulfone (PES) ultrafiltration (UF) membrane was fabricated by non solvent induced phase inversion method. The membrane morphology and performance were simultaneously changed because the PES polymer chains were polarized by the DC electric field. As a result, the M-0-DC membrane showed a porous and thinner separation layer structure with a water permeability of 280.1 L m−2 h−1·bar−1, which is ∼55% higher than that of M-0. Further, a novel antifouling PES membrane containing carbon quantum dots (CQDs) with a concentration of 0.5 was prepared combined with the electric field. The water permeability (∼164% higher than M − 0) of M-0.5-DC was substantially improved and the rejection rate for BSA was 98.4%. The M-0.5-DC also exhibited excellent antifouling property, that is, its BSA flux recovery rate reached as high as 95.3%. Apart from, the Congo red self-cleaning ability investigation of M-0.5-DC showed that the membrane became clean again after the irradiation of ultraviolet light for 2 h. The simultaneously enhanced water permeability and improved anti-fouling property by DC electric field and CQDs are promising advances that may promote the applications of UF membranes in water treatment.

Validation and optimization of a new instrument for measuring the performances of ultrafiltration membranes

Abstract In this study, we introduce the current situation of the membrane inspection industry. We have developed a new integrated rapid membrane inspection machine (MIM) to test the performances of nanofiltration or ultrafiltration membranes by measuring the silt density index (SDI) value (i.e., the key performance indicator) of the water filtered. This study optimizes many key conditions include temperature, pH value and pressures, then establishes a new SDI detection method of ultrafiltration membranes by using MIM. We set the temperature of the test liquid to 25 °C, pH in the range of 7–8, and pressure to approximately 0.10 MPa. The results reflect that MIM can be used to effectively determine the SDI of ultrafiltration membranes using the new method and the results of the method validation are satisfactory.

Conductive 3D networks in a 2D layer for high performance ultrafiltration membrane with high flux-retention and robust cyclic stability

A series of highly performing ultrafiltration membranes have been recently developed, but it is still a withstanding challenge that the ultrafiltration membrane can retain both high flux and high retention ratio without sacrificing the cycle life. In this paper, we construct a novel conductive 3D network in a 2D layer for polyethersulfone membrane, which is self-assembled by graphene oxide, carbon nanotubes, and polyaniline based on the non-solvent induced phase-inversion separation method. The unique 3D network structure and the distinctive selective layer of polyethersulfone membrane possesses molecule transport channels, double-layer intercepted area, and rigid hybrid structure, which contributes effectively to the small molecule's flux, high molecule's retention, and the membrane cyclic stability. The fabricated ultrafiltration membrane exhibits high retention of solute molecules (over 99%), high flux, and extended life span and stability, due to the improvement in the anti-fouling property. Furthermore, the pseudocapacitance of the conductive polymer polyaniline is used to in-situ monitor the fouling behavior, in order to achieve precise decontamination and prolong the long-term life. The results show that the prepared membrane would have high potential applications in relevant environmental separation processes.

High performance ultrafiltration membrane by coupling magnetic migration and in-situ surface modification

Ultrafiltration (UF) membrane technology has drawn much attraction during the past decades to address the challenge of global clean water scarcity. Herein, we proposed a facile methodology to prepare a gradient polysulfone-based (PSf) UF membrane with effective antifouling properties via coupling magnetic field-assisted directional migration and in-situ hydrolysis of fluoro-agent during non-solvent induced phase separation (NIPS). The effect of GO-Fe3O4 gradient distribution and fluorosilane (FAS) in-situ surface modification on membrane morphology, hydrophilicity, porosity, water flux and antifouling properties have been investigated. Optical microscopy and SEM-EDX observations indicated that hydrophilic GO-Fe3O4 nanofiller could directionally migrate in casting solution and eventually result in gradient distribution in PSf matrix under the magnetic field. In addition, the surface enrichment of GO-Fe3O4 provided reaction sites to anchor low energy FAS via in-situ hydrolysis on the membrane surface and realized dual antifouling mechanism (fouling-resistance and fouling-release), which guaranteed UF membranes with excellent antifouling properties and remarkable long-term stability and reusability. Our study provided a new incentive to the development of high performance UF membranes by coupling magnetic migration and in-situ surface modification.

Inhibition of algae-induced membrane fouling by in-situ formed hydrophilic micropillars on ultrafiltration membrane surface

Inhibiting algae-induced membrane fouling has become an extremely challenging work in algae-laden water treatment. In this study, we developed a novel Polyvinylidene Fluoride (PVDF) ultrafiltration membrane to inhibit algal fouling by in-situ formed four-arms star poly(styrene)-block-poly(ethylene oxide)monomethacrylate (FAS-PS-b-PEGMA) micropillars on membrane surface via nonsolvent induced phase separation technique. Morphology characterization revealed that the protruding micropillars were formed on membrane surface after the addition of FAS-PS-b-PEGMA. The formation of micropillars affected phase separation behaviors, resulting in more porous membrane structure. Surface analyses suggested that the hydrophilic PEGMA chains of the amphiphilic copolymers were enriched onto the surfaces of micropillars, and endowed the modified membranes with higher hydrophilicity and lower electronegativity. The excellent permeability and antifouling properties of the modified membranes were demonstrated by gravity-driven filtration of Microcystis aeruginosa solution. Especially for M5 membrane, the stable permeation flux was more than 5 times than that of the control membrane. The flux decline ratio was only 51.3%, which was much lower than the control membrane (80.1%). Furthermore, the analyses of fouling layer further confirmed that the micropillars could inhibit the accumulation of algae cells on the membrane surface. This study provides a one-step strategy on the modulation of ultrafiltration membrane preparation, modification and performance for algae-laden water treatment.

Ultralow Ti3C2TX doping polysulfate membrane for high ultrafiltration performance

Incorporating hydrophilic nanomaterial fillers into a polymeric matrix enables a high-performance ultrafiltration membrane. 2D Ti3C2TX nanosheets are promising candidates due to their hydrophilic nature and good dispersion ability in the organic solvent. In this study, novel polysulfate (PSE)/Ti3C2TX ultrafiltration membranes were prepared by non-solvent induced phase separation (NIPS) method. The phase inversion process of the PSE/Ti3C2TX casting membranes was visualized. Ti3C2TX nanosheets could tune the phase inversion process effectively and promote the phase inversion speed with an ultralow content of 0.05 wt%. As a result, the hydrophilic property and porosity of PSE/Ti3C2TX membrane could be improved. The skin layer thickness was significantly reduced, resulting in saliently ultrafiltration performance, i.e., a pure water flux (PWF) of 685 L*m−2*h−1 (LMH) with a bovine serum albumin (BSA) rejection of 97%. The proposed ultralow Ti3C2TX doping in the casting solutions method offers a versatile platform to manipulate the phase inversion progress during the industrially NIPS process, and enhanced the separation performance of ultrafiltration membranes.

A Mini-Review of Enhancing Ultrafiltration Membranes (UF) for Wastewater Treatment: Performance and Stability

The scarcity of freshwater resources in many regions of the world has contributed to the emergence of various technologies for treating and recovering wastewater for reuse in industry, agriculture, and households. Deep wastewater treatment from oils and petroleum products is one of the difficult tasks that must be solved. Among the known technologies, UF membranes have found wide industrial application with high efficiency in removing various pollutants from wastewater. It is shown that the search for and development of highly efficient, durable, and resistant to oil pollution UF membranes for the treatment of oily wastewater is an urgent research task. The key parameters to improve the performance of UF membranes are by enhancing wettability (hydrophilicity) and the antifouling behavior of membranes. In this review, we highlight the using of ultrafiltration (UF) membranes primarily to treat oily wastewater. Various methods of polymer alterations of the UF membrane were studied to improve hydrophilicity, the ability of antifouling the membrane, and oil rejection, including polymer blending, membrane surface modification, and the mixed membrane matrix. The influence of the type and composition of the hydrophilic additives of nanoparticles (e.g., Multiwall carbon nanotubes (MWCNT), graphene oxide (GO), zinc oxide (ZnO), and titanium dioxide (TiO2), etc.) was investigated. The review further provides an insight into the removal efficiency percent.

Robust, small diameter hydrophilic nanofibers improve the flux of ultrafiltration membranes.

In this study, we systematically investigated the flux performance of ultrafiltration (UF) membranes functionalized with randomly-accumulated nanofibers. By electrospinning nanofibers from hydrophobic polysulfone (PSf) and hydrophilic cellulose (CL), we were able to explore the role that bulk nanofiber (NF) layer thickness, individual NF diameter, and intrinsic chemistry have on composite membrane flux. Additional parameters that we systematically tested include the molecular weight cut-off (MWCO) of the base membrane (10, 100, and 200 kDa), flow orientation (cross-flow versus dead-end), and the feed solution (hydrophilic water versus hydrophobic oil). Structurally, the crosslinked PSf nanofibers were more robust than the CL nanofibers, which lead to the PSfNF-UF membranes having a greater flux performance. To decouple the structural robustness from the water affinity of the fibers, we chemically modified the PSf fibers to be hydrophilic and indeed, the flux of these new composite membranes featuring hydrophilic crosslinked nanofibers were superior. In summary, the greatest increase in flux performance arises from the smallest diameter, hydrophilic nanofibers that are mechanically robust (crosslinked). We have demonstrated that electrospun nanofiber layers improve the flux performance of ultrafiltration membranes.

Effect of operating conditions on the performance of multichannel ceramic ultrafiltration membranes for cattle wastewater treatment

Ceramic membrane has been widely used in treatment of wastewater. In this study the performance of multichannel ceramic membranes in cattle wastewater treatment was studied under different operating conditions, including varied membrane pore size, transmembrane pressure (TMP), cross-flow velocity (CFV), operating temperature, and feed pH. According to the results, the optimal operating conditions were: membrane pore size – 50 nm, TMP – 0.2 MPa, CFV – 4 m/s, operating temperature – 40 ℃, and original pH. Applying these conditions, cattle wastewater treatment concentration experiments were conducted, and the results showed that the membrane could operate up to a concentration factor of five, exhibiting suspended solid, turbidity, and total phosphorus removal rates of 100 %, 99.20 %, and 80.21 %, respectively. In addition, the membrane maintained stable performance through five independent cycles. These findings are expected to help facilitate an efficient ceramic membrane treatment for livestock and poultry breeding wastewater.

Performance of Single and Two-Stage Cross-Flow Ultrafiltration Membrane in Fractionation of Peptide from Microalgae Protein Hydrolysate (Nannochloropsis gaditana)

Cross-flow ultrafiltration (UF) membrane with two different configurations; single (10 kDa and 5 kDa) and two-stage (10/5 kDa) in fractionating microalgae protein hydrolysate (MPH) were studied to obtain a low molecular weight of peptide. The effect of flow rate, trans-membrane pressure (TMP), and pH in fractionating MPH were evaluated based on permeate flux and peptide transmission. The results showed that, for single UF membrane, optimum operating parameters were at a flow rate of 23 mL/min, TMP of 1.5 bar, and pH of 9, with permeate flux of 43.65 L/m2 h (10 kDa) and 55.42 L/m2 h (5 kDa) and peptide transmission of 58.20% (10 kDa) and 67.34% (5 kDa). Meanwhile, for two-stage (10/5 kDa) UF membrane, the best parameters were observed at a flow rate of 23 mL/min, TMP of 1.5 bar, and pH of 2, with permeate flux of 69.85 L/m2 h and peptide transmission of 79.13%. Fractionation of MPH with two-stage UF membrane was observed to be better at producing a low molecular weight of peptide compared to single UF membrane. In conclusion, it was possible to produce permeate flux with a high amount of low molecular weight of peptide by controlling the operating parameters with the suitable configuration membrane.