Non-solvent Induced Phase Inversion Method Research Articles

The anti-fouling and mechanism of Fe3O4@PVDF catalytic membrane in-situ coupling Fenton oxidation for organic pollutants removal

Polyvinylidene fluoride (PVDF) membrane is a promising technique for deep treatment of organic wastewater. However, the unavoidable membrane contamination greatly restrictions its field of application. Herein, we successfully prepared Fe3O4@PVDF membrane with excellent anti-fouling and catalytic ability by non-solvent induced phase inversion method. Meanwhile, Fe3O4@PVDF membrane was characterized by SEM, XRD, FTIR, Water contact Angle and membrane aperture analyzer. The properties of separation and anti-fouling were also evaluated by cross flow filtration of humic acid (HA). Compare with pristine membrane, the pure water flux, rejection rate and FRR respectively increase from 556.81 L m-2 h−1, 65.42 %, 68.26 % to 656.96 L m-2 h−1, 99.64 %, 90.17 % under in-situ Fenton reaction condition. In addition, further mechanistic insights by XDLVO theory, 3D-EEM and EPR verified that high anti-fouling mainly attribute to excellent hydrophilicity of Fe3O4@PVDF and in-situ degradation of HA by OH and 1O2· This work provides insights for improving the separation properties and anti-fouling properties of PVDF membrane in the field of treatment organic wastewater.

Enhancing Water Purification by Integrating Titanium Dioxide Nanotubes into Polyethersulfone Membranes for Improved Hydrophilicity and Anti-Fouling Performance.

Water pollution remains a critical concern, one necessitated by rapidly increasing industrialization and urbanization. Among the various strategies for water purification, membrane technology stands out, with polyethersulfone (PES) often being the material of choice due to its robust mechanical properties, thermal stability, and chemical resistance. However, PES-based membranes tend to exhibit low hydrophilicity, leading to reduced flux and poor anti-fouling performance. This study addresses these limitations by incorporating titanium dioxide nanotubes (TiO2NTs) into PES nanofiltration membranes to enhance their hydrophilic properties. The TiO2NTs, characterized through FTIR, XRD, BET, and SEM, were embedded in PES at varying concentrations using a non-solvent induced phase inversion (NIPS) method. The fabricated mixed matrix membranes (MMMs) were subjected to testing for water permeability and solute rejection capabilities. Remarkably, membranes with a 1 wt% TiO2NT loading displayed a significant increase in pure water flux, from 36 to 72 L m2 h-1 bar-1, a 300-fold increase in selectivity compared to the pristine sample, and a dye rejection of 99%. Furthermore, long-term stability tests showed only a slight reduction in permeate flux over a time of 36 h, while dye removal efficiency was maintained, thus confirming the membrane's stability. Anti-fouling tests revealed a 93% flux recovery ratio, indicating excellent resistance to fouling. These results suggest that the inclusion of TiO2 NTs offers a promising avenue for the development of efficient and stable anti-fouling PES-based membranes for water purification.

A loose polyethersulfone hybrid nanofiltration membrane incorporated with polyethyleneimine-decorated silica nanoparticles for highly-efficient dye/salt separation

Loose nanofiltration (LNF) is a newly-developing technology for desalting dye-containing saline effluents, but suffers from membrane materials with low permeance and poor dye/salt separation selectivity. Herein, a hybrid polyethersulfone (PES) LNF membrane for dye/salt separation was prepared via a nonsolvent-induced phase inversion method, which was carried out using polyethyleneimine (PEI)-modified silica nanoparticles as a dopant. This design not only featured a hybrid PES LNF membrane with high porosity and small mean pore size, but also partially neutralized its charge and enhanced its hydrophilicity. Hybrid PES LNF membrane from a 21-wt% PES solution with 3-wt% PEI-decorated silica nanoparticles addition was demonstrated to achieve high water permeance (92.0 L m−2 h−1 bar−1) and dyes retention ratio (98.4 % for Congo Red, 98.8 % for Nile Blue A, and 95.1 % for Methyl Blue) accompanied with fully-pass for various salts (Na2SO4, NaCl, MgCl2 and CaCl2). In addition, the hybrid membrane exerted excellent resistances to strong acidic, oxidative and hot water (90 °C) environments and exhibited a pH-sensitive permeability. Multicycle test revealed that the hybrid membrane had high permeance recovery ratio (>92.8 %) and maintained its high dye retention and complete salt permeation even after 10 cycles, manifesting its outstanding fouling resistance and recyclability. Besides, the hybrid membrane repelled 92.6 % of dyes from a simulated wastewater consisting of multiple industry-applied direct dyes and salts after 12 h consecutive test, but allow 100 % of mixed salts passing through the membrane, proving its practical applicability to industrial dyeing wastewater. This study provided a simple and economically feasible route to high-performance LNF membrane production for dye/salt separation, thus popularizing LNF process in dyeing wastewater treatment, organic products purification, and resource recovery.

Preparation of heterogeneous cation exchange membrane and its contributions in enhancing the removal of Ni2+ by capacitive deionization system

Capacitive deionization (CDI), an emerging method to eliminate ions from water at a low cost, has garnered significant interest in recent years. This study evaluates the implication of cation exchange resin loading on the membrane via the nonsolvent-induced phase inversion method. After determining the quantity of resins efficiently loaded on the membrane, it was subsequently utilized as a cation exchange membrane in the membrane capacitive deionization (MCDI) unit to examine the performance removal of Ni2+. The results show that the amount of resins influenced the membrane structure and significantly improved the efficiency of Ni2+ removal. The sulfonic acid group show a strong intensity directly proportional to the quantity of resins based on the FTIR measurement. In conjunction with the enhanced resin amount, ion exchange capacity and water content were increased. Simultaneously, there was an observed elevation in the water contact angle and the roughness of the membrane surface with increased resin amount. In the MCDI unit, membrane M20 (20% by weight resin) was employed to elucidate its roles in the CDI unit, encompassing an examination of various concentrations and flow rates, with Ni2+ utilized as a test contaminant. The results demonstrated that using membrane M20 in the MCDI (MCDI-M20) unit consistently exhibited higher adsorption levels than the CDI unit, reaching 19.80 mg g−1 ACC in the MCDI-M20 unit, while CDI unit achieved 10.27 mg g−1 ACC at 200 mg L−1 Ni2+ concentration and a flow rate of 10 mL min−1 at 1.2 V. Additionally, Ni2+ concentrations and flow rates in CDI system had an evident impact on the duration of adsorption due to the mechanisms of ions transport on the membrane. This study suggests that employing the prepared membrane in the MCDI unit enhanced the removal of Ni2+ from the solution, contributing to sustainable development goals.

Polyethersulfone membrane modified by zwitterionic groups for improving anti-fouling and antibacterial properties

Ultrafiltration (UF) membranes are commonly confronted with threats from pollutants during long-term operation. The zwitterions with high hydrophilicity are expected to be the critical material to improve the anti-fouling and antibacterial abilities of membranes. Herein, a new zwitterionic polyethersulfone (PES) (zwitterionic PES - ZPES) was synthesized. The as-prepared ZPES was used to fabricate a zwitterionic UF membrane via the non-solvent induced phase inversion (NIPS) method. Zwitterionic polymer skeleton enhanced the hydrophilicity, permeability and anti-fouling properties of the material. As a result, the ZPES membrane exhibited doubled water flux growth (269.6 L·m−2·h−1) compared with that of the PES (125.3 L·m−2·h−1) and high protein rejection (98.6%). Besides, the ZPES membrane could maintain an excellent flux recovery rate (94.1%) and antibacterial effect (more than 95%). Therefore, the excellent anti-fouling and antibacterial abilities of the ZPES membrane broaden its application scope further.

A P(VDF-HFP) and nonwoven-fabric based composite as high-performance gel polymer electrolyte for fast-charging sodium metal batteries

Although sodium metal batteries (SMBs) have drawn numerous attentions as the promising candidate for the next-generation rechargeable batteries, various issues hinder their practical applications, e.g., the growth of dendrites and large volume change of Na metal during cycling, etc.. The adoption of gel polymer electrolyte (GPE) is an effective solution to address the safety issues and increase the lifetime of SMBs. In this study, a novel composite membrane consisting of nonwoven fabric as the supporting matrix and poly (vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) as the Na+ transmission medium is easily fabricated via non-solvent induced phase inversion method. After plasticized by NaClO4-based liquid electrolyte, the obtained composite membrane exhibits an enhanced mechanical strength, high uptake to organic liquid electrolyte (115%), high thermal and electrochemical stability, superior ionic conductivity (1.38 mS cm−1) and remarkable Na ion transference number (0.47), which has been demonstrated to effectively suppress the growth of sodium dendrite, improve the fast-charging performance and cycling stability of the corresponding SMBs. This work paves a way for the commercialization of GPE in the fast-charging SMBs.

Incorporation of 2D-biotene to polyethersulfone ultrafiltration membrane with superhydrophilicity and antifouling properties for removal of organic pollutants

Here, for the first time, one or few-layer exfoliated 2D-Biotene (E-BIT) was prepared by a cost-effective liquid-phase exfoliation of economical and accessible bulk biotite (B-BIT). The successful preparation of E-BIT was further verified by different characterization methods. XRD pattern demonstrated that B-BIT's basal spacing was increased from 10.07 Å to 11.02 Å. Also, the transparency of the E-BIT to the electron beam showed its small thickness after exfoliation, which was confirmed by AFM results, too. This natural material was utilized as an efficient nano-additive to improve the properties of polyethersulfone (PES) polymeric membrane. E-BIT blended membranes with various quantities (0–2 wt%) were prepared via the non-solvent induced phase inversion method. Small holes at the up layer, coarse finger-like holes and macro-voids at the sublayer were seen in asymmetric prepared membranes. Modification caused the improvement of the membranes' hydrophilicity, which the contact angle was reduced from 69.3 to 53.4 for bare PES and 1 wt% E-BIT blended membranes, respectively. 1 wt% E-BIT blended membrane illustrated flux enhancement of 198.8 L/m2 h, and high elimination efficiency of bovine serum albumin (99%), reactive red 195 (97.8%), reactive green 9 (93.5%), and reactive blue 19 (88.4%), with improved flux recovery ratio of 73%.

One-pot preparation of a carboxylated nanocrystalline cellulose from oil palm fronds as hydrophilic additive for enhancement of membrane permeability and anti-fouling properties

Most polymeric membranes, including polyethersulfone (PES), are limited in their application due to their low water flux and high fouling characteristic. In this study, carboxylated nanocrystalline cellulose (C-NCC) embedded PES membrane was fabricated using the non-solvent induced phase inversion (NIPS) method to enhance the water permeability and anti-fouling properties of the PES membrane. Herein, we synthesized our C-NCC from oil palm fronds (OPFs) using a simple and time-efficient one-pot mixed acid hydrolysis method. The as-prepared C-NCCOPF exhibited a rod-like structure with dimensions of 121.03 ± 65.30 nm and 15.64 ± 5.42 nm in length and width, respectively. The degree of oxidation value of 0.21 was obtained, comparable to those C-NCC synthesized using the classical TEMPO or APS oxidation procedures. By incorporating C-NCCOPF nanorods into the PES matrix, the hydrophilicity, pore structure, mean pore size, porosity, and pure water flux of the modified membrane were significantly enhanced. The Hermia model and Bolton's combined fouling model were applied to investigate the anti-fouling properties of the fabricated membrane during the HA filtration at 1 bar operating pressure. The results demonstrated that the pristine PES membrane was susceptible to fouling which is likely related to the hydrophobic nature of the PES polymer. In contrast, it was discovered that incorporating the C-NCCOPF into the PES membrane could significantly reduce fouling and enhance membrane performance.

High-performance self-healing composite ultrafiltration membrane based on multiple molecular dynamic interactions

The inevitable membrane damage during the use of separation membrane seriously affects the separation and purification effects. Herein, we first synthesized a novel poly(aryl ether sulfone) material containing boronic acid groups (PES-H2BO2) through molecular design, then PES-H2BO2 ultrafiltration membrane was prepared via non-solvent induced phase inversion method. Further, the PES-H2BO2 ultrafiltration membrane and polyvinyl alcohol (PVA) hydrogel were composited by hydrogen bonds and reversible boronate ester bonds between the two to fabricate a series of novel PVA hydrogel/PES-H2BO2 composite ultrafiltration membranes. Through the ultrafiltration experiment of polyacrylamide (PAM) solution, the flux and retention rate changes of the composite ultrafiltration membrane in the initial stage, damage stage, self-healing stage, and stabilization stage were tested and analyzed. The results confirmed that the composite membrane has the ability to rapidly restore the flux and retention rate to the pre-breakage levels through a self-healing effect within 15 min after being damaged, demonstrating their outstanding self-healing characteristics. The design strategy of fabricating composite ultrafiltration membrane with excellent self-healing performance by forming hydrogen bond and reversible boronate ester bond between hydrogel and membrane matrix in this study provides a convenient and feasible way for the design and preparation of high-performance self-healing separation membranes.

Modified emulsion polyvinyl chloride membranes for enhanced antifouling and dye separation properties by introducing tungsten disulfide (WS2) nanosheets

In this study, the fabrication and modification of emulsion polyvinyl chloride (EPVC) membranes were studied using tungsten disulfide (WS2) nanosheets. The layered WS2 nanosheets were synthesized, characterized, and applied in the modification of EPVC membranes. The nonsolvent induced phase inversion method was utilized to fabricate new membranes by introducing the WS2 nanosheets into the polymeric solutions with different percentages. The performance of the fabricated membranes was characterized and evaluated using scanning electron microscopy, atomic force microscopy, attenuated total reflection-Fourier transform infrared, mean pore radius, porosity, contact angle analyses, pure water flux, fouling parameters, rejection tests for bovine serum albumin (BSA) and two dyes, and long-term and reusability tests. The results indicated that the use of WS2 nanosheets in the membrane structure up to the optimum value (1 wt%) increased the water flux and improved the antifouling properties. The pure water flux enhanced from 56.4 L/m2.h in the bare membrane to 191.2 L/m2.h in the 1 wt% WS2/EPVC membrane. In addition, the flux recovery ratio parameter increased from 64.7% to 83.5%. dye rejection rates of 94.7% and 97.8% were obtained for Reactive Red 195 and Reactive Green 19, respectively. Reusability tests for the 1 wt% WS2/EPVC membrane indicated a slight flux drop and negligible BSA rejection changes. Long-term tests showed very high stability in dye rejection and a negligible flux drop.

Fabrication of Polyamide-6 Membranes-The Effect of Gelation Time towards Their Morphological, Physical and Transport Properties.

Porous polyamide-6 membranes were fabricated via a non-solvent induced phase inversion method, and the influence of gelation time on the properties of the membranes was investigated. Membrane samples with various gelation times were prepared. The evaluation of the membranes’ properties was carried out by various analyses and tests, such as scanning electron microscopy, atomic force microscopy, contact angle, wet and dry thickness, mean pore size measurements, porosity, water uptake, mechanical resistance, hydrodynamic water fluxes, membrane hydrodynamic permeability, and retention testing. The scanning electron microscopy images (both surface and cross-section) demonstrated that the increase in gelation time from 0 (M0) to 10 (M10) min led to the morphological change of membranes from isotropic (M0) to anisotropic (M10). The wet and dry thickness of the membranes showed a downward tendency with increasing gelation time. The M0 membrane exhibited the lowest bubble contact angle of 60 ± 4° and the lowest average surface roughness of 124 ± 22 nm. The highest values of mean pore size and porosity were observed for the M0 sample (0.710 ± 0.06 µm and 72 ± 2%, respectively), whereas the M10 membrane demonstrated the highest tensile strength of 4.1 MPa. The membrane water uptake was diminished from 62 to 39% by increasing the gelation time from 0 to 10 min. The M0 membrane also showed the highest hydrodynamic water flux among the prepared membranes, equal to 28.6 L m−2 h−1 (at Δp = 2 bar).

Impact of graphitic carbon nitride nanosheets in mixed- matrix membranes for removal of heavy metals from water

Removal of heavy metal ions from water is being a challenge and Polysulfone (PSf) membranes have shown great potential to remove them from contaminated solutions. In this work, the introduction of Graphitic carbon nitride nanosheets (g-C3N4) into PSf membranes was implemented to improve the permeability and separation performance of PSf membranes. g-C3N4 was incorporated into the membrane matrix via nonsolvent induced phase inversion method. The prepared mixed matrix membranes showed enhanced performances towards water filtration. The incorporation of g-C3N4 into the membrane matrix caused an increase in the desired physicochemical properties like hydrophilicity and surface charge density. This in turn enhanced the rejection of heavy metal ions. The presence of free –NH2 groups on the surface of the membrane helps in increasing the water permeability of the mixed matrix membranes. At 1 bar pressure, the mixed matrix membranes showed rejections higher than 95, 80, and 70 % for lead, cadmium, and arsenic, respectively. Anti-fouling properties of PSf membrane were also enhanced by g-C3N4, which was due to a notable increase in hydrophilicity and the formation of hydration layer on the membrane, preventing interactions between membrane surface and Bovine Serum Albumin (BSA). These properties could be favourable in fulfilling the need of a potential candidate for filtration of waters contaminated by toxic ions.

One-pot Synthesis of Multifunctional KGM/PDA/PVDF Composite Membrane for Efficient Treatment of Oil–water Emulsion and Dye

A new multifunctional KGM/PDA/PVDF composite membrane was successfully prepared via facile nonsolvent induced phase inversion method. Here, the KGM component consisted of numerous covalent bonds, which could improve the corrosion resistance of membrane materials. The dopamine, as a natural “glue” between PVDF substantial and KGM, is capable of integrating different materials together suitably. The as-prepared membrane possessed superior superhydrophilic/underwater superoleophobic property, great corrosion resistance and antifouling property. The separation efficiency was as high as 99.01%, and could stay relatively stable even in the acid, alkali or high salty environment. Additionally, the membrane had great regeneration performance and could keep stable after 15 cyclic separation, which was appropriate for efficient various oil–water separation process. Moreover, the composite membrane could also effectively separate dyes in different environments and the efficiencies were all more than 91%. All in all, the multifunctional composite membrane with facile preparation method might provide a promising strategy and significant theoretical basis for the efficient separation of oil–water emulsions and dyes.

Development of novel polyether sulfone mixed matrix membranes to enhance antifouling and sustainability: Treatment of oil sands produced water (OSPW)

The β-cyclodextrin-modified graphene oxide nanosheets (CMCD@GO), linked by chemical bonds, was successfully prepared. With it was used as fillers, the new CMCD@GO/Polyether sulfone (PES) mixed matrix membrane (CMCDGOM) was prepared by the non-solvent induced phase inversion method. FTIR, XRD and Raman Spectroscopy were used to demonstrate that CMCD@GO was successfully prepared. And the changes in the cross section and surface roughness of the CMCDGOM were observed using SEM and AFM. The modified CMCDGOM showed the larger and continuous pore size, lower surface roughness, and thinner "active layer", compared to the original GO-loading membrane (GOM). Next, the test results of the interface parameter integrated measurement system showed that the water contact angle of CMCDGOM was reduced to 50.8 ° (with GOM was 60.9 °). Then, through the experiments on the treatment of simulated oil sands produced water (OSPW), we have demonstrated the modified CMCDGOM had the higher removal efficiency (from 87.2 to 94.6%), better hydrophilicity (Jw =117.3 L•m−2•h−1, 4 bar), more excellent anti-fouling and sustainable performance (higher flux recovery and lower total flux reduction) than the original COM. The results indicated that the introduction of CMCD@GO can significantly enhance the OSPW treatment capacity of original GO mixed matrix membrane.

Scalable and low-cost fabrication of hydrophobic PVDF/WS2 porous membrane for highly efficient solar steam generation

Solar steam generation based on the light-to-heat conversion via photothermal materials has been considered as one of emerged technologies for utilizing solar energy to produce clean water. Here, a hydrophobic PVDF/WS2 porous membrane for highly efficient solar steam generation was prepared by a scalable and low-cost method. The WS2 photothermal materials were fabricated through a simple ball milling, and then a non-solvent induced phase inversion method was used to fabricate the porous PVDF/WS2 membrane. The PVDF/WS2 evaporator could absorb the sunlight of 90.58% from UV to NIR region due to the multiscattering of the porous structure and the synergistic effect of WS2 and seawater. Moreover, the PVDF/WS2 evaporator exhibits the hydrophobic properties. Taking the advantages mentioned above, our evaporator could manifest the evaporation rate of 4.15 kgm−2h−1 with the solar thermal efficiency of 94.2% under 3 sun irradiation, as well as an outstanding durability upon continuous running. Also, the evaporator shows both the excellent seawater desalination and sewage treatment ability. Outdoor experiments illustrate that the evaporator has practical applications under a natural sunlight condition. The numerous advantages of our PVDF/WS2 evaporator, including the high solar-thermal efficiency, the outstanding durability, and the simple and scalable manufacture process, may provide a potential photothermal material for the commercial solar desalination application and wastewater treatment.

Lignin separation from black liquor by mixed matrix polysulfone nanofiltration membrane filled with multiwalled carbon nanotubes

Carbon nanotubes (CNT)/polysulfone (PSf) mixed matrix membranes (MMM) were prepared by the non-solvent induced phase inversion method and applied in the separation of lignin from black liquor (BL). Three different type of membranes were developed to minimise the fouling phenomenon, which is one of the major concerns regarding the application of polymeric membranes for BL fractionation. The effect of CNT on the filtration and morphological properties were investigated by analyzing pure water flux, porosity, mean pore size, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and water contact angle. These analyses indicated that with increasing the nanotubes content (0–0.5%) resulted in an increase of ≈ 3 times in the mean pores size, water flux (14.8–132.5 Lm−2 h−1 at 15 bar), porosity (74.4–79.7%) and reduction of surface roughness of the prepared membranes. The performance of these membranes was analyzed in terms of lignin rejection and fouling resistance using standard lignoboost lignin solution at various pressures and compared with a commercial polyethersulfone membrane. It was observed that reduction in the permeate flux was lowest (~10% at 12 bar) in the 0.5% CNT-based membranes. However, in terms of lignin rejection, the highest (80–98%) and lowest (52–76%) values were achieved with the simple PSf membrane (0% CNT) and 0.1% CNT membrane, respectively. Further, fouling studies showed that through chemical cleaning, the initial flux was completely recovered for CNT-based membranes without disturbing their flux and rejection behavior. Among the 3 types of prepared membranes, 0.5% CNT membranes showed a good balance between permeate flux and lignin rejection. The application of these membranes for nanofiltration of industrial BL, pre-treated by ultrafiltration, allowed to reach 82–84% rejection for lignin and 37–42% for hemicelluloses. This suggests a significant degree of selective separation of lignin from BL using CNT-based MMM.

Demulsification Performance of Superhydrophobic PVDF Membrane: A Parametric Study

Oil-water separation using hierarchical-structured superhydrophobic and superoleophilic membranes have been recently received remarkable attention. In this study, a polyvinylidene difluoride (PVDF) based membrane was prepared by a non-solvent induced phase inversion method for oil-water emulsions separation. The influences of the two key parameters, namely the concentration of emulsifying agent and water content of the feed emulsion, on the membrane performance were investigated in terms of the permeate flux and water rejection. Span-80, distilled water and n-eptane were employed as an emulsifying agent, dispersed phase and continuous phase, respectively. Results showed that an increase in the emulsifier concentration led to a decrease in the oil permeate flux and water rejection. The emulsifier concentration had the most significant effect on the oil-water separation compared with the water content in the feed emulsion. In a continuous experiment lasted for 120 h, more than 95% water rejection was maintained but with a significant drop in oil flux. The well-structured superhydrophobic PVDF membrane showed promise for water-in-oil emulsion separations.

Fabrication and Characterization of PVDF/UiO-66(Zr) Mixed Matrix Membrane on Non-Woven PET Support

Polyvinylidene fluoride (PVDF) membranes, enhanced with metal-organic framework (MOF), were fabricated on a non-woven polyethylene terephthalate (PET) support using the non-solvent induced phase inversion (NIPS) method to produce mixed matrix membrane (MMM). Polymer concentration of 10%, 15%, and 20% were used in the study whereas UiO-66(Zr) was used as a MOF filler. The resulting membranes were characterized in terms of their morphology, porosity, wettability, mechanical strength, pure water flux, and gas permeability. Results show that the presence of UiO-66(Zr) filler improved membrane morphology, mechanical strength, and hydrophobicity of MMM as compared to pristine PVDF.

Adsorption removal of tetracycline from water using poly(vinylidene fluoride)/polyaniline-montmorillonite mixed matrix membranes

In this study, the porous poly(vinylidene fluoride)/polyaniline-montmorillonite mixed matrix membranes (noted as the PVDF/PANI/MT membrane) were prepared using a non-solvent induced phase inversion method. The amounts of poly(vinylidene fluoride) (PVDF), polyvinylpyrrolidone (PVP), polyaniline (PANI), and montmorillonite (MT) were adjusted such that the synthesized membrane presented appropriate sponge-like structure. Results revealed that the PVDF/PANI/MT membrane with 20.0 wt% PVDF, 3.3 wt% PVP, 5.0 wt% PANI, and 12.0 wt% MT in the solvent N-methyl-2-pyrrolidone achieved the highest removal of antibiotic tetracycline (TC) from water. The adsorption isotherms of TC on the prepared membranes were well fitted by the Langmuir equation, which yielded an adsorption capacity of TC of 51.0 mg/g at 25 °C and pH 6.0 on the PVDF/PANI/MT membrane. Using 0.05 mol/L of NaOH solution, the used PVDF/PANI/MT membrane could be regenerated up to 81%. The reusability of the prepared mixed matrix membrane was also examined and the cross-flow filtration-adsorption tests were finally conducted to evaluate the feasibility of the membranes for continuous operation.

Preparation and Characterization of Polyphenylsulfone (PPSU) Membranes for Biogas Upgrading.

Asymmetric polyphenylsulfone (PPSU) membranes were fabricated by a non-solvent induced phase inversion method. Glycerin and silica nanoparticles were added into the polymer solution to investigate their effects on the material properties and gas separation performance of prepared membranes. The morphology and structure of PPSU membranes were analyzed by scanning electron microscopy (SEM), the surface roughness of the selective layer was analyzed by atomic force microscopy (AFM), and the surface free energy was calculated based on the contact angle measurements by using various solvents. The gas separation performance of PPSU membranes was estimated by measuring the permeability of CO2 and CH4. The addition of glycerin as a nonsolvent into the polymer solution changed the cross-section structure from finger-like structure into sponge-like structure due to the delayed liquid-liquid demixing process, which was confirmed by SEM analysis. The incorporation of silica nanoparticles into PPSU membranes slightly increased the hydrophilicity, which was confirmed by water contact angle results. PPSU membrane fabricated from the polymer solution containing 10 wt.% glycerin showed the best CO2/CH4 selectivity of 3.86 and the CO2 permeability of 1044.01 Barrer. Mixed matrix PPSU membrane containing 0.1 wt.% silica nanoparticles showed the CO2/CH4 selectivity of 3.16 and the CO2 permeability of 1202.77 Barrer.