Ultrafiltration Mixed Matrix Membranes Research Articles

PES mixed-matrix ultrafiltration membranes incorporating ZIF-8 and poly(ionic liquid) by microemulsion synthetic with flux and antifouling properties

Polyethersulfone (PES) mixed-matrix membranes (MMMs) incorporating a co-nanofiller of ZIF-8 and poly(ionic liquid) were constructed via a facile one-pot microemulsion strategy, aiming to increase the flux and anti-fouling properties of the original PES membranes. First, ZIF-8 nanoparticles were synthetized in the reverse microemulsion using 1-butyl-3-methylimidazolium (BmimOTF) ionic liquid as a surfactant and 1-vinyl-3-ethylimidazolium tetrafluoroborate (VeimBF4) polymerizable ionic liquid as an oil phase. Subsequently, the oil phase VeimBF4 in the reverse microemulsion was polymerized, and a latex containing ZIF-8 nanoparticles and poly(VeimBF4) was formed. Finally, MMMs were constructed by blending the latex with PES via the phase-inversion method. The microstructures of ZIF-8 and the MMMs were characterized by TEM, SEM, FTIR, XRD, and XPS analysis. Results showed that the mean size of ZIF-8 are small (10 ∼ 35 nm). Addition of the poly(VeimBF4) and ZIF-8 nanoparticles increased the pore size and hydrophilicity of MMMs. The maximum water flux was 105 L m−2·h−1·bar−1 and 90% flux recovery were obtained after five cycles of filtration, and little decrease of WCA appeared on all MMMs after the repeated experiment, indicated the good stability of MMMs. Compared with PES ultrafiltration membrane, pure water flux and flux recovery rate of the MMMs increased by 15 and 2.8 times respectively.

Performance study of hydroxyapatite cow bone based polysulfone mixed matrix membrane: Effect of hydroxyapatite morphology

In this work, polysulfone (PSf)/hydroxyapatite (HAp) ultrafiltration mixed matrix membranes (MMMs) were prepared for wastewater treatment by using phase inversion method. The effect of hydroxyapatite (HAp) dispersion on the PSf/PVP membrane surface were investigated. Characterizations were done to observe the distribution of HAp on the membrane surface by using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The XRD analysis showed the crystallinity of the HAp derived from cow bone. The dispersion of HAp in polymer matrix is a promising materials that can change the structure of the PSf membrane.

Evaluation of morphology, performance and fouling tendency of mixed matrix PVDF ultrafiltration membranes incorporated by different size-controlled SAPO-34 nanozeolites

In this research, the influences of the size and concentration of synthesized SAPO-34 nanozeolites on the morphological characteristics, water permeability and anti-fouling properties of PVDF/SAPO-34 ultrafiltration mixed matrix membranes were explored and compared with incorporation of commercial SAPO-34. The SAPO-34 is a hydrophilic zeolite with high pore volume, which nominates itself to improve permeation properties of the PVDF membranes when incorporated into its matrix. The nature, size and shape of the synthesized SAPO-34 zeolites as well as the PVDF/SAPO-34 membrane structure were characterized by XRD, EDX and SEM techniques. Evaluation of contact angle and porosity revealed that when the SAPO-34 nanozeolites concentration in the casting solution and their crystallization time (during synthesis) augments up to 1 wt% and 18 h, respectively, the hydrophilicity and bulk porosity of PVDF membranes as well as their surface mean pore sizes enhances. As a result, the pure water flux of all membranes containing SAPO-34 nanoparticles was higher than that of the bare membrane. The lowest contact angle of 73º, the highest bulk porosity of 65%, mean pore size of 3.5 nm and pure water flux of 33 GFD belonged to the membrane which was prepared with 1 wt% of SAPO-34 with 18 h of crystallization time. FRR measurements expressed that the fouling tendency of the membranes containing synthetic SAPO-34 nanoparticles has declined compared to the bare PVDF membrane and those with commercial type. The results approved that by decreasing of the nanoparticle size, the performance of nanocomposite membranes improved.

Synthesis and characterization of novel PES/GO-g-PSS mixed matrix membranes with outstanding antifouling and dye rejection properties

In this study, a novel mixed matrix ultrafiltration membrane based on polyethersulfone (PES) was prepared by embedding graphene oxide-g-polystyrene sulfonate (GO-g-PSS) nanoplates into the polymer matrix by using the phase inversion method. The GO-g-PSS nanoplates were synthesized by using the ATRP method, based on which the ATRP initiator was first grafted onto pre-modified graphene oxide (GO-NH2), and subsequently, the polymerization process was carried out in the presence of monomers. Water contact angle and porosity measurements were both employed for characterization of the prepared membranes. Additionally, the structure and morphology of all the prepared membranes were evaluated by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was also found that, using these nanoparticles, water flux, porosity and hydrophilicity of membranes remarkably increased. Moreover, the more the modified GO loading amount increased, the more the roughness of the prepared membranes increased. The performance of all the prepared membranes was also investigated in terms of rejection, flux recovery and fouling parameters. Accordingly, the retention of two dyes and bovine serum albumin (BSA) molecules was tested, by which the effects of mean pore size, dimensions of permeated molecules and hydrophilicity of the membrane surface were analyzed. It was demonstrated by the fouling test that the 0.75wt% GO-g-PSS/PES membrane sample could provide the highest FRR value (89.9%) and the lowest irreversible fouling resistance (Rir) value (10.1%).

Halloysite Nanotube-Ferrihydrite Incorporated Polyethersulfone Mixed Matrix Membrane: Effect of Nanocomposite Loading on the Antifouling Performance.

Membrane filtration is an attractive process in water and wastewater treatment, but largely restricted by membrane fouling. In this study, the membrane fouling issue is addressed by developing polyethersulfone (PES)-based mixed matrix membranes (MMMs) with the incorporation of hydrophilic nanoparticles as an additive. Ultrafiltration MMMs were successfully fabricated by incorporating different loadings of halloysite nanotube-ferrihydrates (HNT-HFO) into a polyethersulfone (PES) matrix and their performance was evaluated for the separation of bovine serum albumin (BSA) solution and oil/water emulsion. The results show that wettability is endowed to the membrane by introducing the additive aided by the presence of abundant -OH groups from the HFO. The loading of additive also leads to more heterogeneous surface morphology and higher pure water fluxes (516.33–640.82 L/m2h) more than twice that of the pristine membrane as reference (34.69 L/m2h) without affecting the rejection. The MMMs also provide much enhanced antifouling properties. The filtration results indicate that the flux recovery ratio of the modified membrane reached 100% by washing with only distilled water and a total flux recovery ratio of >98% ± 0.0471 for HNT-HFO-loaded membranes in comparison with 59% ± 0.0169 for pristine PES membrane.

Binary metal oxides incorporated polyethersulfone ultrafiltration mixed matrix membranes for the pretreatment of seawater desalination

AbstractIn this study, an attempt was made to pretreat seawater using polyethersulfone (PES) mixed matrix membranes (MMMs) incorporated with titania‐based binary metal oxides. Two different titania‐based binary metal oxides were prepared, namely titania‐zirconia (TiZr) and titania‐zinc oxide (TiZn). The influence of hydrophilic and negatively charged sulfonated poly(ether ether ketone) (SPEEK) polymer as additive of PES MMMs was also studied. Morphological and elemental analysis revealed that both ZrO2 and ZnO were well dispersed in the as‐prepared binary metal oxide TiZr and TiZn, respectively.. Thermogravimetry analysis indicated the good compatibility of TiZr and TiZn with the SPEEK/PES polymer. The binary metal oxide incorporated SPEEK/PES MMMs exhibited improved hydrophilic properties with a low water contact angle of 57° ± (0.6). SPEEK/PES MMMs incorporated with 0.5 wt% TiZr exhibited the highest permeability of 3.11 × 10−7 ± (0.2) m/s·kPa. Seawater pretreatment performance of membranes evaluated using natural organic matters containing high salinity feed water. TiZr and TiZn incorporated SPEEK/PES MMMs exhibited 95% rejection for humic acid. SPEEK/PES MMMs loaded with 0.5 wt% TiZr also showed the highest water flux and 87% water recovery within 90 min of seawater filtration. Both PES/SPEEK/TiZr and PES/SPEEK/TiZn MMMs exhibited superior antibacterial activity.

In Situ Growth of Cationic Covalent Organic Frameworks (COFs) for Mixed Matrix Membranes with Enhanced Performances.

Covalent organic frameworks (COFs) are increasingly utilized as doping agents for the design of advanced ultrafiltration mixed matrix membranes, thanks to their prominent nanoporosity and excellent polymer compatibility. However, current strategies are largely limited in the complicated postaddition of neutral COF particulates. Herein, cationic COFs, namely, TpEB, with sizes down to ∼39 nm are in situ synthesized in polyacrylonitrile (PAN) solution as crystalline fillers for the production of highly permeable TpEB-PAN ultrafiltration membranes. After the condensation of monomer pairs, the growth of cationic TpEB crystallites is restrained due to the electrostatic interaction with negatively charged PAN chains, leading to the formation of a homogeneous TpEB-incorporated casting solution. During the subsequent nonsolvent-induced phase separation process, TpEB crystallites facilitate exchange between the solvent and the nonsolvent because of their hydrophilic and nanoporous nature, accelerating the rate of phase inversion to form a highly porous membrane surface. Thus-prepared TpEB-PAN membranes deliver a tight rejection of BSA with water permeance of up to 380 L m-2 h-1 bar-1, which is 35.6% higher than that of the original PAN membranes prepared without TpEB. The TpEB-PAN membranes also exhibit enhanced operation stabilities and fouling resistances. This in situ growth strategy suggests a new avenue for the preparation of advanced mixed matrix membranes.

PVDF mixed matrix ultrafiltration membrane incorporated with deformed rebar-like Fe3O4–palygorskite nanocomposites to enhance strength and antifouling properties

A novel PVDF mixed matrix ultrafiltration membrane was prepared by blending PVDF with the deformed rebar-like Fe3O4–palygorskite nanocomposites (MPGS) using the chemical coprecipitation method. Fe3O4 nanoparticles were anchored on the surface of the palygorskite nanofibers to form deformed rebar-like structures. MPGS were then distributed uniformly on the membrane matrix. PVDF chains firmly wrapped by the deformed rebar-like nanocomposites consequently enhanced the tensile strength of the PVDF membrane. At 7.0 wt % MPGS, the tensile strength increased from 1.59 MPa to 2.66 MPa. The overall thickness, skin layer thickness, finger-like voids, average pore size and surface roughness of membranes decreased with increasing amounts of MPGS. The rejection of the membrane increased to 99.09% at 7.0 wt % MPGS. The contact angle of membranes decreased from 99.14° (pure PVDF) to 78.76° (PVDF/7.0 wt % MPGS). On the other hand, the pure water flux of membranes increased from 123.57 L m−2 h−1 (pure PVDF) to 356.16 L m−2 h−1 (PVDF/7.0 wt % MPGS). The flux recovery rate of the mixed matrix membranes (PVDF/7.0 wt % MPGS) was as high as 80%. This was more than twice that of the pure PVDF membrane (31.6%). These results demonstrated that the deformed rebar-like structure of the MPGS played a critical role in determining the structures and properties of PVDF mixed matrix ultrafiltration membranes. The hydrophilicity, thermal stability, permeation flux and antifouling property of the mixed matrix membranes increased with addition of MPGS. As such, PVDF/MPGS membranes had excellent comprehensive properties thus making them ideal for application in numerous fields.

Fabrication of polycarbonate ultrafiltration mixed matrix membranes including modified halloysite nanotubes and graphene oxide nanosheets for olive oil/water emulsion separation

In this study, ultrafiltration polycarbonate mixed matrix membranes (MMMs) were synthesized to remove the olive oil from the aqueous solution. To characterize the synthesized membranes in terms of surface morphology, functional groups, hydrophilicity, and mechanical strength, various analyses such as FESEM, FTIR, contact angle, and tensile strength were carried out, respectively. Modified halloysite nanotubes and graphene oxide nanosheets with the loading of 0.25, 0.5, and 0.75 wt% were added to the blank membrane. Membranes including modified halloysite nanotubes exhibited better hydrophilicity and higher pure water flux due to the presence of amphiphilic sodium dodecyl sulfate surfactant at higher nanoparticle loadings, while the agglomeration of graphene oxide nanosheets in the membrane polymeric matrix resulted in the lower pure water flux compared to the blank PC membrane. Moreover, the pure water flux data were modeled by Design-Expert software, and the highest pure water flux of 1340 L/m2 h was reported for PC-MHNT0.75 MMM. Then, the optimized membranes based on the output of the design expert software were used in the ultrafiltration tests for olive oil removal. All the selected membranes reached 100% rejection efficiency of olive oil; however, they were different based on the time to reach this efficiency and the permeate flux. Performance evaluation of membranes in ultrafiltration tests at different feed concentrations showed that the PC-MHNT0.75 mixed matrix membrane possessed the lowest time (165 min at 100 ppm feed concentration) to reach 100% rejection efficiency and subsequently selected as the optimal membrane. The regeneration process using 20% (v/v) acetone solution was implemented for the optimal membrane and the obtained membrane water flux after three cycles of regeneration was more than 96%, introducing the fabricated MMMs as suitable candidates for olive oil separation.

Polysulfone/MMT Mixed Matrix Membranes for Hexavalent Chromium Removal from Wastewater

Polysulfone (psf)/nanoclay mixed matrix ultrafiltration membranes with N-methyl pyrrolidone as a solvent and polyvinylpyrrolidone (PVP) as porogen were prepared using phase inversion techniques. Unlike the other nanocomposites membranes prepared using nanoclays, the present work deals with the incorporation of montmorillonite clay (MMT) and MMT modified with methyl dihydroxy ethyl hydrogenated tallow ammonium (mMMT) to psf matrix as nanoparticle to improve the performance of the membrane. The amount of PVP is optimised by analysing porosity and equilibrium water content. The thermal, chemical and morphological characterisation is carried out using X-ray diffractometer, thermal gravimetric analyser, FTIR and scanning electron microscopy. From the studies, it is found that membrane with 0.6% PVP has higher porosity with a lower contact angle. The water flux and chromium (VI) ion rejection were studied using a crossflow filtration unit. The MMT and mMMT concentration was varied from 1 to 5% and found that polymer nanocomposite membrane (psf/mMMT) with 3% mMMT is having higher rejection and flux. Antifouling performance of the pristine membrane, psf/MMT and psf/mMMT membrane was conducted using bovine serum albumin as organic foulant. The flux recovery ratio of psf/mMMT membrane with 3% mMMT increased to 83%, which is higher than the pristine polysulfone membrane, and the total fouling is reduced to 39%.

Effect of oxidation degree of GO nanosheets on microstructure and performance of polysulfone-GO mixed matrix membranes

Graphene oxide with increasing degree of oxidation (GO-x) were incorporated in polysulfone (PSF) mixed-matrix ultrafiltration membranes. Synthesized GO-x were characterized for average particle size by AFM and DLS method; oxygen functionalities and nanostructure properties by XPS, FT-IR, XRD, Raman analysis, TEM, and elemental analysis; surface charge by zeta potential. Increasing oxidation degree, increased the proportion of carbonyl functional groups, exfoliation, lowered zeta potential and particle size in GO. GO-x with higher oxidation degree showed significantly improved dispersibility in N-methyl-2-pyrrolidone and polysulfone matrix. Blending hydrophilic GO-x, enhanced phase-separation kinetics improving porosity, tensile strength, permeability, protein rejection, and fouling resistance of membranes. With the increase in the oxidation degree of the matrix, contact angle and surface charge on the membranes decreased. 2%-GO-7/P membrane showed permeate flux of 352 kg m−2 h−1 bar−1 while, 1%-GO-7/P membranes acquired permanent negative charge and displayed permeability of 250 kg m−2 h−1 bar−1 with BSA rejection of about 97%, compared to control membrane permeability of 102 kg m−2 h−1 bar−1 with BSA rejection of about 91%. Thus, the membrane flux-rejection trade-off is overcome. 1%-GO-7/P membrane displayed exceptional flux recovery of over 99% on simple DI water flushing. The superior performance of GO-x/P membranes is attributed to faster diffusion rate of water across GO matrix over that through the polymer solution, which increased the number of thermodynamic instabilities giving higher rate of phase inversion resulting in narrow pore size distribution and higher pore density, demonstrating simple approach for enhancing performance of UF membranes.

Fabrication and characterization of polyvinyl chloride mixed matrix membranes containing high aspect ratio anatase titania and hydrous manganese oxide nanoparticle for efficient removal of heavy metal ions: Competitive removal study

AbstractIn this study, novel polyvinyl chloride (PVC) ultrafiltration mixed matrix membranes (MMMs) containing high aspect ratio anatase titania (ANT) and hydrous manganese oxide (HMO) nanoparticles were synthesized in order to decontaminate cadmium and copper metal ions. ANT and HMO nanoparticles with various loadings in a range of 5‐15 were used in the casting solution of MMMs. The characterization of fabricated MMMs was carried out with respect to the structural morphology, hydrophilicity, and composition by scanning electron microscopy (SEM), water contact angle, and Fourier transform infrared spectroscopy (FTIR), respectively. With an increase in the nanoparticle loadings, the change in other membrane characteristics such as mean pore size, pure water flux, and porosity were also evaluated. The results revealed that the mean pore size and water flux increased at a higher loading of ANT and HMO nanoparticles, while the contact angle and porosity of the membranes showed reverse trends. Moreover, the higher flux of pure water was obtained for PVC‐ANT MMMs compared to PVC‐HMO MMMs because of the larger mean pore size, higher porosity, and hydrophilicity of PVC‐ANT MMMs. In this study, the decontamination of cadmium and copper metal ions in single and binary systems of heavy metals was investigated and the effect of Mn2+ (as an interfering ion) was also studied. The evaluation of the metal ion removal data demonstrated that the affinity sequence of both the PVC‐ANT‐15 and PVC‐HMO‐15 MMMs for heavy metal removal was Cu2+ > Cd2+ > Mn2+ in the single and binary systems. It was found through ultrafiltration (UF) experiments that PVC‐ANT MMM was the most efficient membrane in the elimination of heavy metals due to the superior ANT adsorption capacity. However, the overall findings disclosed that both ANT and HMO nanoparticles are suitable candidates for the preparation of MMMs used in cadmium and copper decontamination from aqueous solutions.

Cellulose acetate based biopolymeric mixed matrix membranes with various nanoparticles for environmental remediation-A comparative study

Aluminium oxide (Al2O3) and nano zerovalent iron (nZVI) nanoparticles blended cellulose acetate-polysulfone (CA-PSF) ultrafiltration mixed matrix membranes (MMMs) were successfully prepared via phase inversion method for the removal of dyes and metal ions from wastewater. The dye degradation is very difficult because of structure and low biodegradability nature. At the same time, removal of heavy metals from water also a challenging task. In this study, removal of methylene blue (MB) dye and Cu (II) metal ions as a great environmental concern. There are many techniques available for the removal of these pollutants such as chemical precipitation, adsorption etc. Now-a-days, membrane separation has been extensively used for the treatment of wastewater due to their operational simplicity, low energy consumption and environment friendly nature. In this study, bare CA-PSF (M1) and nanoparticles incorporated MMMs like CA-PSF/Al2O3 (M2) and CA-PSF/nZVI (M3) were prepared, characterized and compared for their rejection and filtration performances. The modified membranes have high rejection values 91 and 94% for MB dye and for Cu (II) the rejection values of 84 and 88% for M2 and M3 membranes respectively than bare membrane. Surface roughness, morphology, cross sectional structure and nanoparticles distribution in the membranes were examined by AFM, SEM and TEM. Membrane performances in terms of pure water permeability and antifouling were also assessed. The fabricated membranes showed outstanding capacity to take care for contaminated water.

Enhancing the performance of a hybrid porous polysulfone membrane impregnated with green Ag/AgO additives derived from the Parkia speciosa

The use of green and environmental-friendly resources is a priority in scientific research nowadays. In this study, the seeds, pods and leaves of the Parkia speciosa were used as a reduction agent in the green synthesis of Ag/AgO nanoparticle additives. The synthesized Ag/AgO nanoparticles were blended into a polymer dope during the preparation of a porous asymmetric PSf mixed-matrix ultrafiltration membrane by the phase-inversion method. Analysis on the structural properties proved that the nanoparticles had a small average of particles size (34.65 nm). A morphological analysis showed the modified membrane, which had been impregnated with Ag/AgO nanoparticles (1.0 wt %) derived from the leaves (PL), achieved the optimum properties and increased permeation of water flux, rejection of humic acid, and anti-fouling, with the lowest internal resistance, besides a large antibacterial inhibition ring. This demonstrated that the existence of green Ag/AgO additives enhanced the function of the hybrid polymer-based ultrafiltration membrane.

Guanidyl-functionalized graphene/polysulfone mixed matrix ultrafiltration membrane with superior permselective, antifouling and antibacterial properties for water treatment

Mixed matrix membranes blended with graphene-based nanomaterials have great potential in water and wastewater treatment on account of their multiple functionalities. To solve the complicated biofouling problem and diversify the applications of membranes, novel synergistic antibacterial guanidyl-functionalized graphene/polysulfone (GFG/PSF) mixed matrix ultrafiltration membranes were prepared by a non-solvent induced phase separation method. The guanidyl-functionalized graphene nanosheets were achieved by a two-step grafting process consisting of amination and guanidination and exhibited high dispersibility in the casting solution, which showed good compatibility with the polymer matrix. Besides the advantages of partially reduced graphene oxide (GO) nanosheets in creating a stronger interaction with the bacterial cell membrane to destroy the bacteria, the induced bidendate binding between guanidyl groups and phosphate groups on the cell wall can make high sterilization rate even at low concentrations. Different techniques including XRD, FTIR, XPS, SEM, TEM, EDX, contact angle meter, filtration and antibacterial experiments were employed to characterize and investigate the performance of nanosheets and membranes. Compared with pure PSF membrane, the GFG/PSF mixed matrix membranes not only exhibited superior permeability and prominent antifouling property performance toward bovine serum albumin (BSA), but also displayed excellent antimicrobial activity and long-term duration toward Escherichia coli and Staphylococcus aureus.

Carboxyl-functionalized covalent organic framework as a two-dimensional nanofiller for mixed-matrix ultrafiltration membranes

A new carboxyl-functionalized covalent organic framework (referred to as COF hereafter, unless otherwise noted) contains aromatic backbones and carboxyl-functionalized nanopores has been synthesized and used as a two-dimensional (2D) nanofiller in polyacrylonitrile (PAN) polymer matrix of ultrafiltration (UF) membranes. A series of mixed-matrix UF membranes with various concentrations COF ranging from 0 to 0.8 wt% have been investigated using non-solvent induced phase separation (NIPS) method. The effect of COF concentration has been evaluated on the membrane morphology, intrinsic and mechanical properties, separation performance, and fouling propensity. Increasing COF concentration from 0 to 0.8 wt% could significantly enhance the rejection rate from 3.5 to 81.9 wt% for bovine serum albumin (BSA) and 65.0–99.4 wt% for γ-globulin. Moreover, membrane hydrophilicity greatly increased, with the decrease of water contact angle from 64.4° to 45.3°. Overall, compared to the pristine PAN membrane, the mixed-matrix PAN membrane with 0.8 wt% COF demonstrated high water flux of 940 L m−2 h−1 bar−1, better protein retention rate, thermal stability, mechanical properties, and fouling resistance.

Novel high throughput mixed matrix membranes embracing poly ionic liquid-grafted biopolymer: Fabrication, characterization, permeation and antifouling performance

We report a simple and effective protocol for preparation of a poly-ionic liquid (PIL)-grafted chitosan Schiff base (PILCSB) and titanium oxide nanoparticles (TNPs) for application as an antibiofouling nanocomposite in the fabrication of new polysulfone (PSU) ultrafiltration mixed matrix membranes (MMMs). The effect new additive (PILCSB@TNPs) on the porosity texture, pure water flux (PWF) and antibiofouling profile for modified MMMs was investigated. Interestingly, the surface hydrophilicity of these MMMs was remarkably enhanced in comparison to the neat PSU membrane (M0) as revealed from wettability and water contact- angle results (wettability/water contact angle = 29.18%/93.48° and 83.46%/57.35° for M0 and MMM6, respectively).

Polysulfone/nanocomposites mixed matrix ultrafiltration membrane for the recovery of Maillard reaction products

Maillard reaction products like melanoidins present in industrial fermentation wastewaters are complex compounds with various functional properties. In this work, novel ultrafiltration (UF) mixed matrix membrane (MMM) composed of polysulfone (PSF) and nanocomposites was prepared through a phase inversion process for the recovery of melanoidins. Nanocomposites were prepared with acid functionalized multiwalled carbon nanotubes (MWCNTs) as the reinforcing filler for chitosan-thermoplastic starch blend. Higher nanocomposites content in the PSF matrix reduced the membrane permeability and melanoidins retention indicating tighter membrane with surface defects. The membrane surface defects could be sealed with dilute polyvinyl alcohol (PVA) solution. The best performing membrane (1% nanocomposites in 18% PSF membrane sealed with 0.25% PVA coating) resulted in uniform melanoidins retention of 98% and permeability of 3.6 L/m2 h bar over a period of 8h. This demonstrates a low fouling PSF membrane for high melanoidins recovery.

Studies on carboxylated graphene oxide incorporated polyetherimide mixed matrix ultrafiltration membranes

In this work the graphene oxide prepared by the modified Hummers’ method was effectively carboxylated. These carboxylated graphene oxide (c-GO) microsheets was characterized by X-ray diffraction analysis, Raman shift, zeta potential, and their morphology was observed using a high resolution scanning/transmission electron microscopy. Polyetherimide mixed matrix membranes (MMMs) were fabricated by the non-solvent induced phase separation technique with varying concentration of this microsheet. The presence of these microsheets on the membrane surface was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy and could also be confirmed visually by optical images. The membranes were further characterized; they showed a greater water flux, higher porosity, and sufficient thermal stability. Incorporation of these microsheets improved the hydrophilicity of the membrane confirmed by the lower contact angle values, which in turn explained the lower interfacial free energy, the increase in work of adhesion, the higher solid-vapor free energy and the spreading coefficient. Membranes loaded with 0.3 wt% of c-GO showed a flux recovery of 94% and only a small flux decline even after 180 min of filtration of humic acid (HA) solution. The efficiency of these membranes in removal of HA, toxic metal ions was also investigated. The bacterial anti-adhesion property of c-GO in the membranes was also explored using Escherichia coli, as a model bio-foulant. The charge of the microsheets and their unique architecture imparts higher hydrophilicity and greater fouling resistance along with improved permeation flux when incorporated into the polymer matrix.

Synthesis, characterization and performance studies of polysulfone and polysulfone/polymer-grafted bentonite based ultrafiltration membranes for the efficient separation of oil field oily wastewater

In this study, polysulfone based mixed-matrix ultrafiltration membranes were prepared by blending polysulfone with different polymer-grafted bentonite additives. Formation of polymer-grafted bentonite was confirmed by Fourier transformed infra-red spectroscopy, energy-dispersive X-ray and thermal gravimetric analysis. Membranes were fabricated via wet phase inversion process with varying additive concentration. Hydrophilicity and structural changes of grafted polysulfone membranes were investigated by scanning electron microscope, water contact angle, molecular weight cut-off and pure water flux measurement. Prepared polysulfone/polymer grafted bentonite membrane was used for the separation of oil from oil-field oily wastewater and the membrane performance was evaluated in terms of permeate flux, oil rejection and fouling characteristics. Finally, results were compared with plain polysulfone and polysulfone/bentonite ultrafiltration membranes.