Polysulfone Ultrafiltration Membranes Research Articles

Enhancement of swimming pool water quality by nanotechnology

Because of the hazards associated with the use of chlorine in pool water treatment, a commercial polysulfone ultrafiltration membrane was utilized. These membranes were coated with varying concentrations of Ag-ZnO nanomaterial (0.05, 0.1, 0.2) and employed in a filter system designed to imitate the swimming pool water treatment process. The experiment lasted three months (April, May, and June) and was carried out for three days each month. The impact of nano-Ag-Zno on the UF nanocomposite membrane was investigated. To analyze the mechanical properties of the membranes, scanning electron microscopy (SEM), porosity, and contact angle were used. The findings reveal that treating the substrates with Ag-ZnO enhanced their hydrophilicity and porosity. Acommercial polysulfone membranes were coated with amixture of Ag-ZnO nanoparticles using the spray pyrolysis technique. The impact of nano-Ag-ZnO on the UF nanocomposite membrane was investigated. To analyze the mechanical properties of the membranes, SEM and contact angle were used. According to the findings, applying Ag-Zno in different concentration to the substrates boosted their hydrophilicity and porosity and aconcentration (2%) could achieve the goal of the research, which is to reduce the use of chlorine disinfection by eliminating Escherichia Coli bacteria, which considered acommon species in swimming pool water.

Optimization of ultrathin polyamide nanofiltration membranes with sulfonated polyethersulfone interlayers for enhanced performance

The “trade-off” effect of nanofiltration membranes may lead to problems of lower flux and higher energy cost, which limit their applications. In this work, an ultra-thin polyamide selective layer (34 nm in thickness, much lower than the conventional polyamide selective layer) was prepared by constructing a sulfonated polyethersulfone interlayer on the surface of polysulfone ultrafiltration membranes by liquid-phase deposition, taking advantage of the inhibitory effect of sulfonated polyethersulfone nanoparticles on the diffusion of piperazine. The prepared nanofiltration membrane exhibits a water flux per unit pressure of 33.2 L·m−2·h−1·bar−1, which is more than 2.5 times higher than that of the nanofiltration membrane without the introduction of the interlayer (12.2 L·m−2·h−1·bar−1). Additionally, it has a high rejection of 98.8 % for Na2SO4, which surpasses the upper limit of the equilibrium of trade-off. The study also delves into the modulation mechanism of the interfacial polymerization process by the presence of a sulfonated polyethersulfone interlayer and explores the potential reasons for the water flux enhancement. This research will likely provide theoretical support and practical experience for further optimization of nanofiltration membrane performance.

Preparation of novel zwitterionic polysulfone ultrafiltration membranes for the dual-enhanced antifouling and antibacterial properties by in-situ one pot crosslinking reaction

Zwitterionic polysulfone (PSf) ultrafiltration membranes were fabricated by non-solvent phase separation (NIPS) method. Herein, a casting solution at 45 °C was developed by using chloromethylated polysulfone (CMPSf), N, N-dimethylacetamide (DMAc) as a solvent, 4-amino-benzenesulfonic acid monosodium salt (ABS) as a cross-linking agent, and Na2CO3 as an acid binder. Simultaneously, the occurrence of the electrophilic substitution reaction between ABS and CMPSf caused the formation of ABS grafting CMPSf (CMPSf-g-ABS). After a specific reaction time, the casting solution was applied to cast membranes, which were subsequently submerged in coagulation bath. A zwitterionic ultrafiltration (ZUF) membrane was obtained using NIPS following the treatment of hydrochloric acid (HCl) solution (1 M mol). Because of the formation of cross-linked CMPSf-g-ABS, the results revealed that the casting solution's viscosity increased sharply from 425.4 mPa s at the initial stage (0 h) to 4810.8 mPa s (22 h). Interestingly, the morphology of the membranes with an asymmetric finger-like structure at 0 h gradually transformed to a gradient sponge-like structure after 22 h. Specifically, the ZUF membrane (M22-H) with the gel fraction of 72.1% procured after the reaction of 22 h demonstrated a low water contact angle (40.17°) and a high pure water permeance (420.4 L m−2 h−1 bar−1). The M22-H also exhibited a high flux recovery rate (FRR) (90.2%), bovine serum albumin (BSA) rejection (>95%), and Escherichia coli (E. coli) antibacterial rate (96.2%). The surface of the ZUF membrane with numerous zwitterionic groups enhances the hydration layer's energy (i region <16 nm) and creates a thick hydration layer (ii region >16 nm), causing a significant improvement in the antifouling performance. This research opens new avenues for preparing zwitterionic functional membranes.

Enhancing the properties and performance of polysulfone ultrafiltration membranes using citric acid based deep eutectic solvent additives

This study focuses on improving the performance of polysulfone (PSF) membranes through modification with a Deep Eutectic Solvent (DES) composed of Citric Acid (CA) and Choline Chloride (ChCl). Various concentrations, ranging from 1.00 wt% to 4.00 wt%, were explored to investigate the impact of DES on membrane properties. The membranes underwent morphological analysis using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Fourier-transform Infrared Spectroscopy (FTIR) was utilized to understand chemical interactions, while mechanical strength and contact angle assessments provided insights into the physical robustness and hydrophilicity of the membrane surfaces. Zeta potential measurements revealed an increase in negative surface charge, particularly notable at 1.00 wt% and 2.00 wt% CA concentrations, which significantly enhanced dye rejection capabilities. Leaching tests were conducted to ensure the environmental integrity of the DES within the membrane structure. The performance metrics of the membranes, including pure water permeability (PWP) and dye rejection, were thoroughly evaluated. Although the 3.00 wt% CA-DES membranes showed high PWP, the 2.00 wt% CA-DES membranes demonstrated the best overall performance, achieving a commendable balance between high water flux, dye rejection, and antifouling properties, with an FRR of 93 %. The Thermal Gravimetric Analysis (TGA) highlighted variations in thermal stability. This study identifies the 2.00 wt% CA-DES modified PSF membrane as the superior choice, offering an unparalleled combination of permeability, selectivity, and antifouling properties. The advancements represented by this membrane mark a significant stride forward in the application of ultrafiltration technology, potentially impacting a wide range of industrial and environmental processes.

PH-responsive P(AA-b-SBMA)-grafted magnetic GO high-performance ultrafiltration membrane with improved antifouling tendency and cleaning efficiency

Nanocomposite ultrafiltration polysulfone membrane with pH-responsive surface was designed and synthesized using poly (AA-b-SBMA)-grafted magnetic graphene oxide (MGP) nanofiller. The obtained membranes revealed advanced antifouling, high cleaning-efficiency, and high rejection when compared to pristine PSf membranes. The novel MGP nanofiller was synthesized by copolymerization of acrylic acid and sulfobetaine monomers on the grafted magnetic graphene oxide surface by RAFT polymerization. The non-solvent-induced phase separation was used to prepare polysulfone nanocomposite ultrafiltration membranes with pH-responsive surfaces optimized by the MGP content of 0.05 to 0.3 wt% in the dope solution. The MGP content embedded within the polysulfone matrix greatly influences the water flux. The optimal 144 LMH flux of water, achieved by 0.1 wt% MGP, was almost 80 % higher compared with the pure polysulfone. The optimal MGP-modified nanocomposite membrane showed high antifouling tendency and 72 % flux recovery value. Also, when pH changed from 3 to 8, the pH-responsive membrane revealed the best water flux recovery for bovine serum albumin adsorption-desorption. Comprehensive characterization of MGP nanofiller, the modified polysulfone, and pristine membranes confirmed that the surface hydrophilicity, cross-section morphology, surface roughness, and compositions of the modified ultrafiltration membranes could be modified considerably by the incorporation of MGP nanofiller.

Mixed matrix composite membranes based on Pebax and nano-amorphous MIP-202 for CO2 separation

Membrane-based separation technology for carbon capture has received increasing attention in the world due to low energy consumption, investment and operating cost. However, the simultaneous improvement in selectivity and permeance has faced large challenge for mixed matrix membranes owing to limited affinity sites and transport channels. Herein, the nano-scale MIP-202 (SM-202) was first prepared by inhibited Ostwald ripening strategy during crystal growth, and then nano-scale amorphous MIP-202 (ASM-202) was prepared by thermal chemical reaction. Subsequently, mixed matrix composite membranes (MMCMs) were developed by using ASM-202 as a filler and polyether-block-amide (Pebax) as a polymer matrix, and the hydrophilicity-modified polysulfone ultrafiltration membrane (mPSf) was utilized as a porous support. It is observed that ASM-202 possessed good miscibility with Pebax polymer chains as a result of hydrogen bonds between two phases. Thus, the as-obtained MMCMs showed outstanding CO2 separation performance (CO2 permeance: 936 GPU; CO2/N2 selectivity: 52), which were enhanced by 138 % and 108 % over that of the pristine Pebax membrane, as well as 15.3 % and 13.0 % over that of MMCMs incorporating with SM-202, respectively. The improvement in gas separation performance can be explained by the reason that the nano-scale ASM-202 with large specific surface area afforded more unsaturated metal sites and nitrogen-doped structure, thus improving the CO2 affinity in membranes. Moreover, the loose amorphous structure of ASM-202 provides more transport passageways, which enhanced the diffusion rate of gas molecules through the membranes. Besides, resultant MMCMs maintained great stability for over 360 h using the CO2/N2 mixed gas as feed gas, whose average CO2 permeance and CO2/N2 selectivity fluctuated at 880 GPU and 47.

Polysulfone ultrafiltration membranes fabricated from green solvents: Significance of coagulation bath composition

Even though membranes can lead to more environmentally sustainable separation processes, membrane casting typically involves toxic organic solvents. Recently, there has been increasing interest in substituting these toxic solvents for green solvents. In this study, polysulfone ultrafiltration membranes were fabricated by nonsolvent induced phase separation using two green, bio-derived solvents: Cyrene and gamma-valerolactone (GVL). The effect of coagulation bath composition was investigated, with water, ethanol, and water/ethanol mixtures tested as nonsolvents in the bath. Membranes were characterized and their performance was tested by dead-end filtration. For both Cyrene and GVL, using pure water in the coagulation bath resulted in membranes with residual solvent trapped inside. During dead-end filtration, these membranes were either impermeable (in the case of GVL) or had very low bovine serum albumin (BSA) rejection (in the case of Cyrene). Concentrations of ∼ 50–75 v% ethanol in the coagulation bath led to improved solvent removal and better pore formation, as indicated by scanning electron microscopy. These membranes also had higher flux and rejection. For example, membranes cast using Cyrene with a 65:35 volumetric ratio of ethanol:water in the coagulation bath achieved 70.1 L/m2/h water flux at 2.41 bar and 96.7 % BSA rejection. Additionally, the effect of humidity on membranes cast using GVL was investigated. Membranes cast under moderate humidity had novel surface morphologies with porous dimples ∼ 1 µm wide. Overall, these results show that Cyrene and GVL are promising solvents for preparing polysulfone ultrafiltration membranes. The work highlights the importance of relating membrane properties to casting conditions.

Investigating the impact of stormwater fouling on polysulfone ultrafiltration membranes modified with deep eutectic solvents

In this study, we evaluate the performance of modified polysulfone (PSF) ultrafiltration (UF) membranes, which incorporate deep eutectic solvents (DES), in treating stormwater laden with natural organic matter e.g. chemical oxygen demand (COD) and total suspended solids (TSS). We also aim to understand how these organic substances, e.g. COD, TSS, from the water source contribute to the fouling of the synthesized membranes. PSF membranes were synthesized using a non-solvent induced phase separation technique and integrated with varying concentrations of ChCl:FR (Choline Chloride: D-(−)-Fructose) 1:1 DES. The surface and porous structures of the membranes were characterized through Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurements, scanning electron microscopy (SEM), and mechanical testing. The UF performance of these membranes was assessed and compared with different commercially available UF flat sheet membranes in terms of pure water permeability and antifouling behavior against collected stormwater from a sedimentation pond. Furthermore, the study evaluated the quality of the permeate based on parameters such as COD, turbidity, TSS, pH, and conductivity and compared the permeate quality of a pilot-scale ceramic UF membrane unit. The findings indicate that the inclusion of DES in the polysulfone membrane structure enhances the membranes' antifouling properties and permeability. This research offers valuable insights into the role of DES in the formation of polysulfone UF membranes and their potential for practical use e.g. sedimented stormwater.

Preparation and characterization of PSF/SPSF blended ultrafiltration membranes

Purpose This paper aims to improve the permeability and antifouling of polysulfone (PSF) ultrafiltration membranes, the PSF matrix was modified by incorporating sulfonated polysulfone (SPSF). Design/methodology/approach Systematic investigations were conducted on the synergistic effects of a pore-forming agent, coagulation bath temperature and SPSF doping in the casting solution on blended ultrafiltration membranes. The chemical composition of the membranes was analyzed using Fourier transform infrared spectroscopy. The morphology and surface roughness of the membranes were characterized using scanning electron microscopy and atomic force microscopy. The hydrophilicity of the membrane surface was analyzed using a contact angle meter. The permeability and antifouling properties of the blended membranes were also investigated through filtration experiments. Findings The results indicated that the blended ultrafiltration membranes demonstrated an optimal overall performance when PVP-K30 content was 5.0 Wt.%, coagulation bath temperature was 30°C and SPSF content was 2.4 Wt.%. In comparison to a pure PSF ultrafiltration membrane, there was a significant increase in pure water flux (390.7 L·m−2·h−1) by 2.2 times, while bovine serum albumin retention slightly decreased to 93.8%. In addition, the flux recovery rate improved by 2.1 times (71.4%) compared to that of the original PSF ultrafiltration membrane. Practical implications The method provided a simple and practical solution for improving the antifouling and permeability of PSF ultrafiltration membranes. Originality/value SPSF was anticipated to serve as an excellent modification additive for the preparation of ultrafiltration membranes with superior properties.

Lignin extraction and fractionation from rice straw biorefinery residues

Crops straw contains many valuable natural compounds. Cellulose and hemicellulose in agricultural wastes have been widely used in biofuel production. However, the large-scale application of residue lignin from biorefinery is still an unsolved problem. Various impurities and heterogeneous lignin with a very complicated molecular weight distribution were generally found in the recovered raw solid products. In this study, brown solid residue from rice straw biorefinery was processed using membrane separation in combination with the soda-ethylene glycol (Soda-EG) process to extract high-purity lignin. At first, wet brown solid was mixed into an aqueous solution of sodium hydroxide and ethylene glycol for lignin fragmentation, depolymerization, and solubilization at elevated temperatures. Afterwards, microfiltration (MF) was applied to recover the dissolved lignin in the filtrate from the extracts. As high as 90% of the lignin in the brown solid could be recovered after acid precipitation of the filtrate. The highest lignin content in the precipitate product could be 90% (dry basis). The precipitate was re-dissolved at high pH aqueous solutions for further molecular weight fractionation by ultrafiltration (UF). The best rejection of high-molecular-weight (>1 × 105 g/mol) lignin was 77%, while low-molecular-weight (<3 × 103 g/mol) lignin was <13% with a MWCO of 10 kDa polysulfone UF membrane in a dead-end filtration system. The cross-flow operation with the same UF membrane showed that >80% lignin could be recovered from the retentate and the flux of permeate could be maintained after three operation-cleaning cycles. Overall, the combined MF-UF operation could be a viable method for obtaining high-value-added lignin products with a specific molecular weight range.

Ultrafiltration study of the polysulfone membrane modified with branched polyethyleneimine

Abstract This work discussed the fabrication of polysulfone (PSF) ultrafiltration membranes with hydrophilic behaviour by adding branched polyethyleneimine (PEI) as an additive. By directly blending the base polymer and the additive in the organic solvent, the casting solution is prepared. An asymmetric ultrafiltration membrane was fabricated by the phase inversion method. The presence of PEI was confirmed by comparing the IR spectra of the plain PSF membrane and the modified PSF membrane. A scanning electron microscope was used for the comparison of morphological changes in plain and modified membranes. The membrane was characterised with respect to bovine serum albumin (BSA) adsorption, pure water flux, permeability, compaction factor, humic acid (HA) rejection, and water uptake. The fouling resistance behaviour is prompted due to the presence of hydrophilic PEI chains in the membrane. As a result, pure water flux and flux recovery ratio increased from 28.84 to 326.54 L/m2h and from 0.526 to 0.954 L/m2hkPa for the modified membrane with respect to the plain membrane, respectively.

Honeycomb-like SBA-15 parceled in 2D GO for ultrafiltration membranes fabrication with ultrahigh permeability and enhanced anti-fouling performance

Novel 3D mesoporous silica SBA-15 and 2D graphene oxide (GO) composite nano-fillers incorporated polysulfone (PSf) ultrafiltration (UF) membranes (GO-SBA-15/PSf) were first prepared via blending modifications by non-solvent induced phase separation (NIPs). 3D honeycomb-like SBA-15 not only improved the surface hydrophilicity but also provided extra nano-channels parceled in 2D GO networks for convenient hydrone transport via confinement-effect. The lamellar GO networks relieved the agglomeration of inorganic materials inside the polymer, anticipating in the interfacial polymerization reaction. GO-SBA-15/PSf UF membranes were systematically investigated using contact angle, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM) and Brunauer-Emmett-Teller (BET) methods. The pure water flux reached 641.7 L m-2h−1 which was 3 times than that of pristine PSf membranes (229.2 L m-2h−1) under the pressure of 0.1 MPa. Negative charge of GO generated electrostatic repulsion with protein, which facilitated a high rejection of 98.22% and excellent FRR value of 85% that was 1.5 times than that of pristine PSf membranes (58%). The UF membranes fabricated by new multidimensional nano-fillers overcame the trade-off effect between permeability and protein rejection.

Facile approach for novel TFC-NF membranes preparation using water soluble poly(vinyl alcohol-co-styrenesulfonic acid) and their characterizations

ABSTRACT This research article first time reports the concept of thin film composite (TFC) membranes preparation using novel functional copolymer based on poly(vinyl alcohol-co-styrenesulfonic acid) (PVA-co-SSA). Polysulfone ultrafiltration membrane was coated by applying PVA-co-SSA solution via eco-friendly method. The selective coating layer was crosslinked by glutaraldehyde (GA) aqueous solution. The effects of PVA-co-SSA and GA solution concentrations used for TFC membranes preparation were evaluated to study the membranes’ characteristics. Infrared and Raman spectroscopy was used to confirm the structural characteristics of composite membranes. The resultant TFC membranes were found hydrophilic (exhibited water contact angle in the span of 41° to 60°) and possessed a smooth surface having surface roughness ranging from 20.9 to 26.3 nm with the selective layer thickness in the range of 123 to 276 nm. Membrane exhibited maximum water flux of 32.78 l m−2 h−1 at when operated in cross-flow cell at 0.69 MPa; at same pressure the membrane gave 74.8% rejection of MgSO4 when fed with 1000 ppm solution of MgSO4; while NaCl rejection of membranes was in the range of 33.75 to 54% when tested using 2000 ppm NaCl feed solution supplied at operating pressure of 1.7 MPa. The trade-off relationship between membrane solute rejection and flux was observed, and composite membranes showed higher rejection of bivalent salt i.e. MgSO4 compared to monovalent salt i.e. NaCl.

Enhancement of polysulfone ultrafiltration membrane with third generation poly(amido amine)-graphene oxide nanocomposite

In this era of rapid industrialization and urbanization, ultrafiltration is identified as a potential technology for wastewater reclamation to reduce the stress on renewable water resources. In this work, graphene oxide (GO) has been functionalized with poly (amido amine) (PAMAM) to produce GO-PAMAM nanocomposite that was embedded in polysulfone membrane matrix produced by phase inversion. The abundance of -OH and -NH2 groups on the synthesized nanocomposites resulted in improved hydrophilicity of the membrane and aided improving the membrane porosity and increased its pore radius. As a result, the membrane pure water permeation flux increased by 1300 % for the new membrane compared to pristine PSF membrane to reach a maximum of 124.5 LMH/bar while maintaining a high BSA rejection rate of 99 % with a flux recovery rate of 55 %. Although the flux recovery rate was low, the improvement achieved in pure water permeation flux while maintaining high BSA rejection makes the produced membrane suitable for future ultrafiltration applications.

Uncovering the effect of poly(ethylene-co-vinyl alcohol) molecular weight and vinyl alcohol content on morphology, antifouling, and permeation properties of polysulfone ultrafiltration membrane: thermodynamic and formation hydrodynamic behavior

Uncovering the effect of poly(ethylene-co-vinyl alcohol) molecular weight and vinyl alcohol content on morphology, antifouling, and permeation properties of polysulfone ultrafiltration membrane: thermodynamic and formation hydrodynamic behavior

Characterization of Polysulfone Membrane with Variation of Ethanol Concentrations in Coagulation Bath for Ultrafiltration Membrane

The aim of this research is to study influence of ethanol concentrations in coagulation bath to charecteristic of physical properties and polysulfone membrane performance. Ethanol concentrations that used is 0; 40; 50; 60 ; 70; 80; 90 %. Process of making for polysulfone ultrafiltration membrane is prepared with phase inversion technique. Polysulfone membrane is made from polysulfone solved in N,N- dimetilacetamida (DMAc) and additive poly(ethylene glikol) (PEG) 600 in proportion 18 %: 77 %: 5 %. The result showed that increasing ethanol concentrations causes the increasing of density and increase concentrations from 0 - 50 % causes increasing swelling degree, but decreasing swelling degree from concentrations 60 - 90 %. However influence of ethanol concentration in coagulation bath to membrane performance is increasing of water flux, permeability coefficient, and rejection coefficient to dextran. It based on of result that polysulfone membrane with ethanol concentrations 80 dan 90 % included membrane classification ultrafiltration by rejection coefficient value above 90 %.

Graphene oxide/chitosan doped polysulfone membrane for the treatment of industrial wastewater

Rapid urbanization and industrialization have created tremendous stress on fresh water sources. Moreover, discharge of industrial wastewater has left public health and environment under high potential risks. In this paper, chitosan-functionalized graphene oxide (GO-CH) was synthesized and incorporated into polysulfone (Psf) ultrafiltration membranes. The concentration of the nanocomposite and the ratio of GO to CH in the nanocomposite were varied to produce different GO-CH doped polysulfone membranes. The effect of GO-CH addition on the morphology and membrane performance was studied through water contact angle, scanning electron microscopy, atomic force microscopy, porosity, pore size, and permeation measurements as well as rejection and antifouling tests, while produced GO-CH nanocomposite was characterized using FTIR and XRD analyses. The GO-CH/Psf membrane exhibited higher water flux, bovine serum albumin (BSA) rejection rate, and water flux recovery ratio, and lower BSA solution flux attenuation rate than pristine Psf membrane. GO-CH/Psf membrane containing 0.085 wt% nanocomposite with GO to CH ratio of 1 to 0.01 had an improved permeate flux of 136%. Maintaining the same GO-CH composition of 0.085 wt% and changing GO to CH ratio to 1:1 resulted in better hydrophilicity (contact angle 68°) and increased reversible fouling from 23 to 33%. The best membrane was further tested with real industrial wastewater obtained from a GTL plant in Qatar showed 28% improvement in COD removal.

Phenol and benzoic acid recovery from end-of-life of polysulfone ultrafiltration membranes and its thermochemical kinetic behaviour

ABSTRACT The remarkable properties of polysulfone (PSF) membranes have contributed to their use in many ultrafiltration applications. Meanwhile, this huge usage of PSF films and its short service life have generated a huge amount of waste PSF films that need to be managed carefully. Within this framework, this is the first research specifically developed to valorize the end-of-life of PSF membranes and convert them into high-value chemical and energy products using pyrolysis treatment. The treatment was performed using a thermogravimetric analyzer (TGA), while the structure and abundance of the phenol and benzoic acid compounds in the generated vapor were determined using Fourier-transform infrared (FTIR) spectroscopy and Gas chromatography-mass spectrometry (GC-MS). Thermogravimetric recorded data at different conditions (5–30°C/min) was subjected to linear and nonlinear models including KAS, FWO, Friedman, Vyazovkin, and Cai to assess the pyrolytic kinetic behavior of PSF films. The films showed higher content of volatile matter (57%), lower NOx emissions (0.321%), and a little bit more SOX emission (6.909%). The GC-MS showed that the pyrolytic gaseous products are rich in phenol (24.3%) and benzoic acid (52.4%) compounds and the highest abundance was achieved at 30°C/min. Whereas activation energies were estimated in the range of 193–240 kJ/mol based on linear kinetic criteria versus 161–163 kJ/mol in the case of nonlinear models, where R2 values (>0.91) indicated perfection. Also, distributed activation energy and independent parallel reaction kinetic models showed a good fit with the TGA-DTG experimental data with the minimum deviation. The study confirmed the potential of pyrolysis treatment in converting wasted PSF films into a new source for the recovery of phenolic and benzoic acid.

Separation Characteristics of Surface Modified Polysulfone Ultrafiltration Membrane using Oxidative Catalytic Polymerization of Aniline

The commercially available Polysulfone (PSF) membrane surface was modified by solution polymerization of aniline using different oxidation catalysts i.e., FeCl3, CuCl2, and APS. Modified membranes were then characterized with respect to physio-chemical properties like surface chemistry, porosity, wettability, surface roughness, morphology, etc. It was observed that the hydrophilicity/ wettability of membranes was increased upon surface modification by polyaniline which again depended on the nature of the oxidation catalyst used. Membranes developed using FeCl3 and CuCl2 as oxidants exhibit improved permeation, protein rejection, and antifouling properties, whereas decrement was observed in modified membrane performance using APS as an oxidant. Among all modified membranes, PSF/PANI-CuCl2 membrane demonstrates the most promising performance in terms of higher pure water flux and protein solution permeation flux i.e., 453.3 L/m2.h and 122.3 L/m2.h respectively. The PSF/PANI-CuCl2 membrane unveils superior resistance towards bio-fouling in comparison to the other modified membranes. Analytical techniques were used for the characterization of the modified membranes such as ATR, XPS, FESEM, and AFM. Contact angle measurement also supports the fact that PSF/PANI-CuCl2 membrane has a better chemical and physiological attachment to the polysulfone membrane surface.

Effect of the Addition of Polyacrylic Acid of Different Molecular Weights to Coagulation Bath on the Structure and Performance of Polysulfone Ultrafiltration Membranes

Membrane fouling is a serious issue in membrane technology which cannot be completely avoided but can be diminished. The perspective technique of membrane modification is the introduction of hydrophilic polymers or polyelectrolytes into the coagulation bath during membrane preparation via non-solvent-induced phase separation. The influence of polyacrylic acid (PAA) molecular weight (100,000, 250,000 and 450,000 g·mol-1) added to the aqueous coagulation bath (0.4-2.0 wt.%) on the polysulfone membrane structure, surface roughness, water contact angle and zeta potential of the selective layer, as well as the separation and antifouling performance, was systematically studied. It was found that membranes obtained via the addition of PAA with higher molecular weight feature smaller pore size and porosity, extremely high hydrophilicity and higher values of negative charge of membrane surface. It was shown that the increase in PAA concentration from 0.4 wt.% to 2.0 wt.% for all studied PAA molecular weights yielded a substantial decrease in water contact angle compared with the reference membrane (65 ± 2°) (from 27 ± 2° to 17 ± 2° for PAA with Mn = 100,000 g·mol-1; from 25 ± 2° to 16 ± 2° for PAA with Mn = 250,000 g·mol-1; and from 19 ± 2° to 10 ± 2° for PAA with Mn = 450,000 g·mol-1). An increase in PAA molecular weight from 100,000 to 450,000 g·mol-1 led to a decrease in membrane permeability, an increase in rejection and tailoring excellent antifouling performance in the ultrafiltration of humic acid solutions. The fouling recovery ratio increased from 73% for the reference membrane up to 91%, 100% and 136% for membranes modified with the addition to the coagulation bath of 1.5 wt.% of PAA with molecular weights of 100,000 g·mol-1, 250,000 g·mol-1 and 450,000 g·mol-1, respectively. Overall, the addition of PAA of different molecular weights to the coagulation bath is an efficient tool to adjust membrane separation and antifouling properties for different separation tasks.