Polysulfone Ultrafiltration Membranes Research Articles

A novel loose nanofiltration membrane with superior anti-biofouling performance prepared from zwitterion-grafted chitosan

BackgroundDeveloping a novel loose NF membrane with zero NaCl rejection as well as effective anti-adhesive and anti-bacterial properties is significant for recycling and purification applications in many industries. Materials and methodA novel anti-biofouling loose nanofiltration (NF) membrane was fabricated by crosslinking a graft copolymer chitosan-g-poly(sulfobetaine methacrylate) (CS-g-PSBMA) as selective layer of a thin film composite (TFC) membrane for dye/salt separation. Specifically, CS-g-PSBMA was synthesized using cerium (IV) ion as the oxidant to initiate the graft polymerization of SBMA from CS. The PSF membrane was pre-wetted with hyperbranched polyethylenimine solution, then the loose NF membrane was fabricated by crosslinking CS-g-PSBMA with glutaraldehyde on the polysulfone (PSf) ultrafiltration membrane as the support layer. Results and discussionUpon optimization, the membranes show minimal rejection rates to NaCl or MgCl2, which is less than 5% but high rejection to dye molecules. After maintaining the pressure for 6 h, the interception rate for Congo red/mixed salts remained at 98% and that for methyl green/mixed salts was 80%. Further, experiment results show that the stable anti-bacterial rates of loose NF membrane against Escherichia coli and Staphylococcus aureus reached 98.3% and 99.0%, respectively.

Modification and acidification of polysulfone as effective strategies to enhance adsorptive ability of chromium (VI) and separation properties of ultrafiltration membrane

AbstractIn order to improve the hydropilicity, polysulfone was first modified by grafting diethanolamine and further made into the ultrafiltration membranes by a phase inversion process. Ultrafiltration membranes were characterized by nuclear magnetic resonance spectrum, contact angle, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, adsorption, and ultrafiltration experiments. The ultrafiltration membrane containing tertiary amine groups had a 99.2% rejection to bovine serum albumin (BSA), 235.2 L m−2 h−1 pure water flux and 78.6% flux recovery rate. Usually, the ultrafiltration membrane containing tertiary amine groups has a low rejection and a poor adsorptive ability to Cr(VI) in the neutral condition. A novel strategy of acidification in advance was adopted to adjust the separation performance of the polysulfone ultrafiltration membrane containing tertiary amine groups. The pre‐acidification strategy could improve the Cr(VI) rejection from below 10% to 100% in the neutral condition, since ultrafiltration membranes acidified in advance did not lose its H+ in storage. Moreover, the acidification could improve the glass transition temperature and only caused a slight decrease of water flux and BSA rejection.

Preparation and characterization of a novel emphatically charged strengthened chitosan composite nanofiltration membrane

In this paper, chitosan was grafted with acrylic acid and positively charged elements, and a series of reinforced nanofiltration membranes were prepared by coating modified chitosan polymer with polysulfone ultrafiltration membrane as support. The structure of chitosan derivatives and polymers was characterized by infrared spectrum, and the membrane structure was characterized by scanning electron microscope and atomic force microscope. The performance of composite nanofiltration membrane was closely related to the structure of polymer and the electrical properties of positively charged elements. The rejection rate of 50% molar ratio composite nanofiltration membrane to CaCl2 reached 97.4%. The corresponding flux is 430.7 Lm-2h-1. The retention order was: CaCl2 > NaCl > Na2SO4. The tensile strength increased by 27.3%. Acid resistance (5%HCl)) was improved by 50.5%. Alkali resistance (5%NaOH) increased by 42.2%. The results showed that the positive charge enhanced chitosan composite nanofiltration membrane had excellent performance. The charge effect had no effect on NaCl and Na2SO4, but had significant effect on CaCl2. The membrane is a typical positive charged nanofiltration membrane suitable for separating high-valent cations from weak acids or weak bases.

Tailoring the dual role of styrene-maleic anhydride copolymer in the fabrication of polysulfone ultrafiltration membranes: Acting as a pore former and amphiphilic surface modifier

• The ring opening of SMA(anh) in NaOH solution enhanced the interaction with PSF. • The transformation of SMA(anh) into SMA enhanced the pore-forming ability. • Long finger-like pores were created on the cross section of PSF/SMA-4 h membrane. • Membrane performances were optimized by the cumulative effects of SMA and PEG. To enhance the membrane performances, amphiphilic copolymers are extensively used to modify polymeric membranes by the surface segregation. Notably, they also act as a pore former in the membrane fabrication by the nonsolvent induced phase separation (NIPS). However, it is rarely reported to systematically adjust the pore-forming ability. Herein, a simple method is proposed to simultaneously adjust the surface segregation and pore-forming ability of styrene-maleic anhydride copolymer (SMA (anh)) in the PSF composite membrane formation by its ring opening reaction in the alkaline environment. The surface segregation and pore-forming ability were obviously enhanced accompanying with the miscibility improvement of dope solutions. Subsequently, the membrane microstructure was further optimized by selecting polyethylene glycol (PEG) as the second additive. Significantly, high-molecular-weight PEG was anchored on the membrane surface via strong hydrogen bonding and chain entanglement with sodium styrene-maleic anhydride copolymer (SMA). Compared with the PSF/SMA (anh) membrane, water contact angle (WCA) was obviously reduced due to the cumulative effects of SMA and PEG. Moreover, the resultant membranes displayed the pure water flux of 415.8 L/m 2 ·h·bar, BSA rejection of 98.3 % and flux recovery ratio (FRR) of 95.15 %, which remarkably excelled those reported values for other similar PSF composite membranes.

Hydrophilic polysulfone ultrafiltration membrane incorporated with reduced graphene oxide modified ZnFe2O4: application in the separation of simulated natural organic wastewater

Hydrophilic polysulfone ultrafiltration membrane incorporated with reduced graphene oxide modified ZnFe2O4: application in the separation of simulated natural organic wastewater

Development of polysulfone ultrafiltration membranes with enhanced antifouling performance for the valorisation of side streams in the pulp and paper industry

One-stage method of polysulfone (PSf) membrane modification by the addition of polyacrylic acid (PAA, Mn = 250 kg·mol−1) to the coagulation bath during membrane preparation via non-solvent induced phase separation (NIPS) was proposed. The effect of PAA concentration on the membrane structure, hydrophilicity, zeta potential, separation performance and antifouling stability in ultrafiltration of lysozyme, polyvinylpyrrolidone (PVP K-30, Mn = 40 kg mol−1) and humic acid model solutions as well as thermomechanical pulp mill process (ThMP) water was studied. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), measurements of the tangential flow streaming potential and water contact angle were used for membrane characterization. It was found that addition of PAA into coagulation bath resulted in decreasing pore size and porosity of the selective layer as well as the formation of a thicker and denser selective layer. Water contact angle of the modified membranes was found to decrease significantly and zeta potential of the selective layer was shown to become more negative in the studied pH range 3–10, all compared to the reference membrane. It was revealed that pure water flux (PWF) decreased and lysozyme and PVP K-30 rejection increased with the increase in PAA concentration in the coagulation bath. It was found that membranes modified with PAA demonstrated better antifouling stability in ultrafiltration of humic acid solution and ThMP process water. Modified membranes were found to have higher flux, fouling recovery ratio and hemicelluloses rejection in ThMP process water ultrafiltration compared to the reference PSf membrane that allows application of these membranes for hemicelluloses concentration and purification.

Incorporation of Biomass-Based Carbon Nanoparticles into Polysulfone Ultrafiltration Membranes for Enhanced Separation and Anti-Fouling Performance.

Functionalized carbon nanomaterials are considered to be an efficient modifier for ultrafiltration membranes with enhanced performance. However, most of the reported carbon nanomaterials are derived from unsustainable fossil fuels, while an extra modification is often essential before incorporating the nanomaterials in membranes, thus inevitably increasing the cost and complexity. In this work, novel functionalized biomass-based carbon nanoparticles were prepared successfully from agricultural wastes of corn stalks through simple one-step acid oxidation method. The obtained particles with the size of ~45 nm have excellent dispersibility in both aqueous and dimethyl formamide solutions with abundant oxygen-containing groups and negative potentials, which can endow the polysulfone ultrafiltration membranes with enhanced surface hydrophilicity, larger pore size, more finger-like pores, and lower surface roughness. Therefore, the separation and anti-fouling performance of membranes are improved simultaneously. Meanwhile, the addition of 0.4 wt% nanoparticles was proved to be the best condition for membrane preparation as excess modifiers may lead to particle aggregation and performance recession. It is expected that these biomass-based carbon nanoparticles are potential modifying materials for improving the separation performance and anti-fouling property of the membranes with great simplicity and renewability, which pave a new avenue for membrane modification and agricultural waste utilization.

Facile low-temperature route toward the development of polymer-supported silica-based membranes for gas separation via atmospheric-pressure plasma-enhanced chemical vapor deposition

The use of inexpensive porous polymers instead of conventional ceramics to support silica-based membranes can potentially minimize the cost of membrane synthesis. To develop polymer-supported silica-based membranes, lowering the high synthesis temperature of the silica-based top layer is essential. In this study, we explore the application of atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) for synthesizing polymer-supported silica-based membranes. The deposition of a continuous silica-based layer on an asymmetric polysulfone ultrafiltration membrane using hexamethyldisiloxane as an organosilicon precursor was achieved at ambient temperature and pressure via AP-PECVD. The gas permeation properties of the AP-PECVD-derived polymer-supported membranes strongly depended on the deposition duration, as prolonged deposition could reduce the remaining defects by covering the entire surface of the support with the plasma-deposited layer. The membranes showed increased selectivities for H2/N2 and H2/SF6 from 2.9 to 9.5, and from 4.5 to 184, respectively, exhibiting gas permeation dominated by molecular sieving. The present study demonstrates that AP-PECVD is a promising strategy for the fabrication of polymer-supported silica-based membranes for gas separation.

Synergetic effects of dodecylamine-functionalized graphene oxide nanoparticles on antifouling and antibacterial properties of polysulfone ultrafiltration membranes

The potential use of dodecylamine-functionalized graphene oxide (rGO-DDA) nanoparticles as an antifoulant and antibacterial nanofiller was investigated. GO and rGO-DDA were analyzed using Raman spectroscopy, FTIR, SEM, TEM, and TGA that all confirmed the successful functionalization of GO structure. Polysulfone (PSF) ultrafiltration membranes incorporating varied loadings of GO and rGO-DDA were then fabricated via phase inversion approach. All membranes were characterized in terms of chemical structure, morphology, hydrophilicity, porosity and mean pore size. Cross-section SEM images showed the distribution of GO and rGO-DDA between the pores and on the polymer walls. AFM results demonstrated that GO addition increased the roughness of membrane; while with rGO-DDA addition the surface became smoother. Pristine PSF and rGO-DDA based membranes exhibited similar hydrophilicity, while GO-based membranes exhibited higher hydrophilicity as revealed by contact angle measurements. Permeability, separation and antifouling experiments were performed in a cross-flow membrane setup and showed that flux decreases with the increase in GO and rGO-DDA concentration. rGO-DDA membranes showed higher antifouling and antibacterial performance compared to the pristine PSF and GO membranes. Neat PSF exhibited 65.4 % flux recovery ratio (FRR) against BSA that was increased to 86.9 % and 89.1 % with GO-0.1 and rGO-DDA-0.1, respectively. Against HA, FRR was improved from 87.8 % for neat PSF to 95.6 % and 99.3 % with GO-0.1 and rGO-DDA-0.1, respectively. Additionally, rGO-DDA membrane exhibited higher bacteriostatis rate (83.6 %) against H. aquamarina than GO membrane (62.9 %). Moreover, rGO-DDA nanoparticles exhibited excellent dispersibility in several solvents making them promising nanofillers for various membranes with high antifouling and antibacterial performance.

Polyvinylamine/ZIF-8-decorated metakaolin composite membranes for CO2/N2 separation

• ZIF-8-d-MK hybrid with the interlayer spaces was developed by coordinating ZIF-8 particles to amorphous MK sheets. • PVAm/ZIF-8-d-MK MMCMs for CO 2 /N 2 separation were successfully fabricated. • The interlayer spaces of ZIF-8-d-MK in the MMCMs function as CO 2 transport pathways. • The ZIF-8-d-MK hybrid was homogenously dispersed in PVAm matrix due to amorphous structure of MK sheets. Mixed-matrix composite membranes (MMCMs) have great potential in chemical separation process due to high performance, but the dispersibility of the filler is an enormous challenge we face. In this study, a ZIF-8-decorated metakaolin (ZIF-8-d-MK) hybrid was prepared by the AlO 4 tetrahedron oxygens in amorphous MK coordinating with the zinc ions of ZIF-8. MMCMs by coating polysulfone (PSf) ultrafiltration membranes with a mixture of hybrid and polyvinylamine (PVAm) were obtained, which can efficiently separate CO 2 from N 2 . SEM and TEM results indicated that ZIF-8 particles were present between the amorphous MK sheets, and the coordination between the two phases was validated by FTIR. ZIF-8-d-MK, with a partially amorphous structure, exhibited homogeneous distribution in the PVAm matrix, as verified by SEM and XRD, and ZIF-8-d-MK had a strong interaction with the polymer matrix as certified by attenuated total reflectance-FTIR. A highest CO 2 permeance of 169 GPU with CO 2 /N 2 selectivity of 86.7 were acquired for MMCMs, loaded with 3 wt% ZIF-8-d-MK under pure gas conditions, which were much higher than those of MMCMs loaded with MK, ZIF-8, or a mixture of MK and ZIF-8. The improved values were primarily ascribed to the well-dispersed ZIF-8-d-MK serving as CO 2 transport pathways because of its molecular sieving effect for CO 2 /N 2 . Importantly, under mixed gas feed conditions, the stability measurement demonstrated that the MMCMs adding 3 wt% ZIF-8-d-MK did long-term operation for over 360 h, and maintained great CO 2 separation performance.

A novel mixed matrix polysulfone membrane for enhanced ultrafiltration and photocatalytic self-cleaning performance

Photocatalytic materials can be used as self-cleaning functional materials to alleviate the irreversible fouling of ultrafiltration membranes. In this work, the small size g-C3N4/Bi2MoO6 (SCB) blended polysulfone (PSF) ultrafiltration membranes was fabricated by hydrothermal and phase inversion methods. As a functional filler of ultrafiltration membranes, the small size g-C3N4 nanosheet decorated on the surface of Bi2MoO6 can enhance the photocatalytic performance for bovine serum albumin (BSA) degradation, and remove irreversible fouling under visible light irradiation. In addition, the introduction of SCB microspheres into PSF matrix obviously increased the porosity of ultrafiltration membranes. Therefore, the SCB-PSF ultrafiltration membranes displayed excellent antifouling performance (flux recovery ratio is 82.53%) and BSA rejection rates (94.77%). SCB-PSF also had high photocatalytic self-cleaning activity, indicating excellent application prospects in organic wastewater treatment.

Cu-TCPP nanosheets blended polysulfone ultrafiltration membranes with enhanced antifouling and photo-tunable porosity

The major obstacle in membrane filtration technology is the membrane fouling, which not only decreases the membrane efficiency, but also enhances its operational cost. In order to fabricate a membrane with antifouling characteristics, potential nanofillers have been added to the engineering polymer(s) to make a composite to improve the membrane efficiency. Herein, we incorporate porphyrin-based ultrathin, highly ordered porous photothermal responsive copper tetrakis(4-carboxyphenyl)porphyrin (Cu-TCPP) nanosheets as a novel nanofillers into the polysulfone (PSf) matrix. High loading (6 wt%) and well dispersed Cu-TCPP nanosheets incorporated polysulfone nanocomposite (Cu-TCPP/PSf) ultrafiltration membranes are prepared via non-solvent induced phase inversion. The Cu-TCPP/PSf composite membranes demonstrate pronounced antifouling and antibiofouling potential along good separation performance. The nanocomposite membranes demonstrate photo-induced pore tuning due to the local heating of photothermal Cu-TCPP nanosheets by visible light, which further improves the membrane separation efficiency. The Cu-TCPP/PSf composite membrane with 6 wt% Cu-TCPP nanosheets enhances the pure water permeance from 23.42 to 260.61 L·m−2·h−1·bar−1, with improved antifouling potential, precise permeance recovery ratio of 99.13% after three cycles, and good separation performance for 100 and 200 nm particles. Considering relatively moderate cost, facile processing, tunable porosity, durable and good mechanical strength along restrained swelling, the Cu-TCPP/PSf membranes are considered as potential candidate as antifouling/antibiofouling ultrafiltration membranes for water purification.

Tuning the hydraulic permeability and molecular weight cutoff (MWCO) of surface nano-structured ultrafiltration membranes

Hydraulic permeability and molecular weight cutoff (MWCO) performance tuning of polysulfone (PSf) ultrafiltration (UF) membrane was attained via surface modification with a tethered layer of poly(acrylic acid) (PAA). Surface nano-structured (SNS) PAA layer was synthesized onto base PSf UF membranes by atmospheric pressure plasma (APP) surface activation followed by graft polymerization (GP) of acrylic acid (AA). Through a systematic study, it was shown that effective SNS-PAA-PSf UF membrane performance tuning was feasible by adjustments of APP and graft polymerization conditions. It was shown, for the first time, that SNS-PAA-PSf membranes can be synthesized with a range of hydraulic permeability (spanning a factor of 1.1–2.6 in magnitude) for a given MWCO, or a range of MWCO (spanning a factor of 1.5–2.3 in magnitude) for a given hydraulic permeability, thereby overcoming the hydraulic permeability-MWCO tradeoff.

Enhanced mechanical strength and performance of sulfonated polysulfone/Tröger's base polymer blend ultrafiltration membrane

To improve the mechanical strength and separation performance of sulfonated polysulfone (SPSf) ultrafiltration membranes, Tröger's base (TB) polymer was blended into the casting solution. An acid-base crosslinking structure between the sulfonic acid groups of SPSf and tertiary amine groups in TB would contribute to their good compatibility and influence the membrane formation process, morphology and properties. The formation of acid-base pairs was confirmed by the existence of quaternary amine groups in the X-ray photoelectron spectra of SPSf/TB blend membranes. According to the pore structure analysis of ultrafiltration membranes, the blending of TB polymer into SPSf enhanced the surface and total porosities, and reduced the top layer thickness. In addition, the finger-like pores became more regular and vertically interconnected. The SPSf/TB blend membrane showed a higher water contact angle than SPSf membrane due to the addition of hydrophobic TB polymer and formation of acid-base crosslinking structure. The SPSf/TB blend membranes showed higher pure water fluxes (127.4–342.7 L m−2 h−1) than the SPSf membrane (51.6 L m−2 h−1). All membranes showed similar retention factor for bovine serum albumin (BSA), a model protein foulant. In static experiments, the amount of BSA adsorbed by the SPSf/TB blend membranes was much lower than that of the pristine SPSf membrane because the enhanced charge of the blend membranes (ζ = −72.46 ~ −79.17 mV) strengthened the electrostatic repulsion between membrane surface and BSA. The flux recovery ratio after three ultrafiltration cycles using SPSf/TB blend membranes was lower than that of SPSf membrane because pore blockage and irreversible pollution occurred more easily under a high flux, larger average pore size, and lower hydrophilicity. The introduction of TB polymer enhanced the mechanical strength of the ultrafiltration membrane due to the formation of acid-base crosslinking structure between TB polymer and SPSf.

High-Flux Fine Hollow Fiber Nanofiltration Membranes for the Purification of Drinking Water

High-flux fine hollow fiber nanofiltration (HFNF) membranes were prepared by interfacial polymerization (IP) using polysulfone (PSF) ultrafiltration (UF) membranes with an outer diameter of 425 μm ...

Graphene Oxide/Polyamide-Based Nanofiltration Membranes for Water Purification

A novel electric field-assisted strategy to fabricate graphene oxide (GO)-functionalized nanofiltration (NF) membranes was reported. The resulting polyamide (PA) NF membranes were formed by interfacial polymerization (IP) of trimesoyl chloride (TMC) in an organic phase and piperazine as well as GO with a concentration between 0.1 and 0.5 in the water phase under an electric field using a polysulfone (PSF) ultrafiltration membrane as a substrate. Due to the electric field-induced repulsion in GO during polymerization, the resulting GO/PA nanofiltration membranes showed a Turing-like structure in the composite functional layer as well as higher hydrophilicity. As a result, a substantially improved water flux was observed, and TFC-G0.3-DC even showed a water permeability of 28.5 L·m–2·h–1·bar–1, which is ∼30% higher than that of its analogue TFC-G0.3 without an electric field. Additionally, the TFC-G0.3-DC NF membrane also demonstrated high rejection rates for Na2SO4 (97.6%) and MgSO4 (97.3%) at 4 bar but relatively low NaCl rejection (25.1%), which suggests that it has the potential to separate divalent and monovalent ions. More importantly, GO-PA composite nanofiltration membranes also exhibited excellent antifouling properties with HA and BSA flux recovery rates reaching more than 95%. The simultaneously enhanced water flux, high divalent/monovalent ion selectivity, and improved antifouling property by the electric field are promising advances that may impact applications of NF membranes in water purification.

Effect of Solvent Evaporation Time of Polysulfone Incorporated Copper Oxide Nanoparticles Incorporated Polysulfone Ultrafiltration Membrane on Protein Removal

Polysulfone (PSf) membranes are becoming more popular in wastewater treatment recently, mostly due to its stability in chemical, thermal and mechanical properties. PSf membranes are hydrophobic, causing difficulty of water permeation. Incorporating metal oxide nanoparticles improving the membrane hydrophilicity, thus increasing membrane permeation and rejection. In this study, copper oxide nanoparticle (CuO NPs) incorporated PSf membranes were fabricated under different evaporation times of 3s, 6s, 8s, and 9s to investigate on membrane morphology and performance. The membrane morphologies were characterized by using scanning electron microscope (SEM) while the membrane performance was determined through pure water flux (PWF) and bovine serum albumin (BSA) rejection. When characterized by SEM, all membranes showed an asymmetric structure with thin and dense at the top while the bottom layer was thick and porous. It was discovered that as the evaporation time increased, the formation of the finger-like structure became narrower while dense layer became thicker. When tested with PWF, membranes with higher evaporation times showed less permeability, decreasing from 139.74 Lm-2h-1 to 89.89 Lm-2h-1. In terms of BSA rejection, increased in evaporation time caused the rejection rate to increase from 87.79% to 92.15%. This study proved that evaporation time is one of important parameters that influences the membrane performance significantly.

Rapid in-situ covalent crosslinking to construct a novel azo-based interlayer for high-performance nanofiltration membrane

The strategy of introducing a hydrophilic interlayer (IL) on the substrate has been widely used in the preparation of nanofiltration (NF) membranes. In this paper, we perform a rapid in-situ coupling reaction of tannic acid (TA) and a dual diazonium salt (DDS) to construct a novel stable azo-based interlayer on the polysulfone (PSf) ultrafiltration membrane. Through exploring the concentration and the deposition time of TA, the protocol of fabricating the interlayer with the optimal hydrophilicity is determined. Relevant characterizations indicate that the thickness of the interlayer is quite thin, and the defects at the surface of the pristine substrates disappear after modification. Interestingly, the color of the substrate with interlayer changes dramatically after pouring piperazine (PIP) solution thereon, implying that there is considerable interaction between the phenolic hydroxyl groups at the interlayer and the PIP molecules in aqueous phase. By further reducing the PIP concentration, an active layer of which thickness is only about 35 nm was obtained. The separation performance evaluation suggests that the optimized novel NF membrane exhibits a 2.71-fold increase in water permeance (17.40 ± 1.09 L m−2h−1 bar−1) compared with the conventional one. Moreover, the discussion about the role of the interlayer on interfacial polymerization (IP) is also provided with advanced significance.

Novel polysulfone ultrafiltration membranes incorporating polydopamine functionalized graphene oxide with enhanced flux and fouling resistance

Novel PSF composite UF membranes incorporating low loadings of polydopamine-functionalized graphene oxide particles (rGO-PDA) were fabricated and investigated. The functionalization was confirmed using FTIR-UATR, Raman spectra, XPS, and SEM. Pristine PSF, PSF/GO, and PSF/rGO-PDA MMMs were then prepared using the phase inversion technique and analysed using FTIR, SEM, AFM, and contact angle (CA). The cross-section SEM images showed better distribution of rGO-PDA particles in the pores and polymer wall whereas the pristine GO particles aggregate and partially block the pores. Thus, the pure water flux increased with the addition of rGO-PDA without affecting the rejection properties, while the flux decreased with the embedding of pristine GO particles. The highest pure water permeability (PWP) was obtained with PSF/rGO-PDA-0.1 to be approximately twice that of the pristine PSF and PSF/GO-0.1. All membranes exhibited complete rejection of BSA and HA, and showed almost similar performance against different dyes. The FRRs of the pristine PSF after three fouling cycles (FRR3) against BSA and HA were recorded to be 57.8% and 70.7% respectively. FRR3 was enhanced by around 30% with PSF/rGO-PDA composites. The MMMs prepared in this work are expected to have great potential on ultrafiltration and similar studies on other membrane processes.

Tailoring the morphology of polyethersulfone/sulfonated polysulfone ultrafiltration membranes for highly efficient separation of oil-in-water emulsions using TiO2 nanoparticles

Polyethersulfone (PES)/sulfonated polysulfone (SPSf)/TiO2 mixed matrix membranes (MMMs) were fabricated using non-solvent induced phase inversion (NIPS) technique for oil-in-water emulsion separation. The performance of the membrane was tailored by tuning the morphology through the addition of TiO2 nanoparticles (NPs) (0.05–0.15 wt %) and by varying the polymer concentrations (18–28 wt). The optimum concentration of TiO2 was found to be 0.075 wt %), where the water permeability and solute rejection trade-off neutralised. In this membrane the polymer concentration was 22 wt %. In terms of performance, the membrane had pure water permeance of 555.2 LMH bar-1, 90% oil rejection and 89.5% permeance recovery rate (PRR) at an initial concentration of 900 ppm. The surface porosity was 13.1%. Molecular dynamic (MD) simulations and spectroscopic analyses proved that the NPs formed hydrogen bonds with the polymer chains. This resulted in two effects with ripple impacts: a) slowed movement of polymer chains or slow solid-liquid phase separation, leading to the MMMs with the thicker top layer and high surface porosity, and b) stable and even distribution of NPs within the framework as observed with elemental mapping. Accordingly, the MMMs obtained desired asymmetric features corresponded to their overall superior performance. In conclusion, small concentrations of TiO2 NPs can be used to successfully modify morphology and separation performance of membranes used for oil-in-water emulsion filtration.