Nanocomposite Membranes Research Articles

Fabrication of High Impact-Resistant Polyimide Nanocomposites with Outstanding Thermomechanical Properties.

Neat polyimide films are known to be dense and rigid. They are therefore not suitable for use in membranes, sensors and sustainable energy storage applications. In this study, a novel technique has been used to simultaneously improve the porosity, rigidity, damping ability and impact resistance of polyimide membranes. It is demonstrated that dispersion of a small amount of polyaniline copolymer-modified clay of about 0.25-0.5 wt.% into the polyimide matrix resulted in an enhanced storage modulus while maintaining high damping ability and glass transition temperature, Tg. Novel polyimide/substituted polyaniline-copolymer-clay nanocomposite membranes containing poly(N-ethyl-aniline-co-aniline-2-sulfonic-acid)-modified-clay (SPNEAC) was successfully prepared and incorporated into the polyimide matrix to form modified clay/polyimide nanocomposites. UV-Vis analysis of the nanocomposite films shows that the optical transparency of the SPNEAC-PI nanocomposite membranes decreased with increasing SPNEAC concentration due to the high UV-Vis absorption of SPNEAC. Transmittance of about 3% was observed in the nanocomposite membrane containing 5 wt.% modified clay at 500 nm wavelength, which is significantly lower than that for the neat PI membrane of about 36%. The dispersion of SPNEAC containing a high concentration of clay (≥40 wt.% clay), in polyimide matrix, resulted in the attainment of a higher degree of imidization than was possible for the organoclay/polyimide nanocomposite. This behavior is believed to be due to the synergistic interaction between PI and SPNEAC. A correlation of the morphology and elastic modulus of the SPNEAC2/PI nanocomposites shows that at low loading of SPNEAC 2 ≤ 0.5 wt.%, the cross-sectional morphology of the composite is an open, spiky, weblike structure with a storage modulus of about 1 GPa, but it progressively evolves into densely packed microspheroids with storage moduli of ≥2 GPa at 10 wt.% SPNEAC2. The impact energy of SPNEAC/PI composites, calculated from the α-transition peak area, increased with increasing SPNEAC loading and were about 4 times that of neat PI at 10 wt.% SPNEAC.

Nanomagnets doped antifouling membrane for fine emulsion separation

Reutilizing domestic and industrial wastewater can be the best solution to global water issues. However, the treatment of oily wastewater is a long-standing problem due to the complex fine emulsion produced by mixing the different types of oils and organic solvents. In this work, nanocomposite membranes were fabricated using phase inversion technique by loading polysulfone matrix with varying amounts of magnetic nanoparticles (MNPs). Developed nanocomposite membrane has shown hydrophilic and super-oleophobic properties with an underwater contact angle of 145 ± 3°. Incorporating MNPs into the Psf membranes enhanced the performance and permeability with the oil rejection efficiency as high as ∼99 %. Psf-MNP composite membranes exhibited remarkable antifouling properties, preventing oil deposition on the membrane surface with improved mechanical properties. Our studies suggest that the developed Psf-MNP nanocomposite membrane shows increased surface functionality, which leads to promising long-term performance and reusability of the membrane.

Does pervasive interconnected network of cellulose nanocrystals in nanocomposite membranes address simultaneous mechanical strength/water permeability/salt rejection improvement?

In this research work, we investigated the effect of two cellulose nanocrystal (CNC)-related parameters, namely aspect ratio and loading content on the mechanical and desalination performance of a cellulose diacetate (CDA) model membrane system. Dispersion of high aspect ratio (HAR) CNCs in the CDA resulted in different types of nanoassembly, represented by evaluating the mechanical efficacy coefficient (CFE), viscoelastic responses and separation performance of the nanocomposite membranes. Accordingly, 0.15 and 0.25 wt% showed random isolated dispersion and tight polymer-nanorod network, while 0.50 and 0.75 wt% conformed to nanorods' pervasive interconnected network (PIN) through side-by-side aggregation and intensive bundle alignment, respectively. Specifically, the nanocomposite membrane containing 0.50 wt% HAR-CNCs simultaneously demonstrated improved mechanical strength along with mitigated water permeability/salt rejection tradeoff for brackish water desalination. This concurrent boosting was attributed to the effective mechanical reinforcement mechanism induced by the percolating network along with its partial aggregation-caused bi-continuous and electrostatically-controlled nano-pathways, orchestrating the separation tradeoff. It confirmed our hypothesis that a nanocomposite membrane with metamaterial characteristic could be obtained via manipulating the dispersion state of CNC rods in the CDA, triggering coincided optimization of mechanical strength and desalination performance.

Preparation of hydrophilic modified ZIF-8 and its application in the preparation of nanocomposite matrix reverse osmosis membrane with improved permeation performance

Preparation of hydrophilic modified ZIF-8 and its application in the preparation of nanocomposite matrix reverse osmosis membrane with improved permeation performance

The amount of improvement and therapeutic effect of sports health by increasing the viscosity of peach juice through reverse osmosis and polymer membrane

In this study, the performance of polyamide membranes embedded with synthesized silica nanoparticles was evaluated for pomegranate juice concentration using the reverse osmosis (RO) process. The research aims to explore the potential therapeutic benefits and measurable improvements in sports health achieved by employing RO and a polymer membrane to enhance the viscosity of peach juice. The membranes utilized in this study feature a multi-layer structure comprising a non-woven polyester layer for strength, a sulfone polyether polymer sheet, and a polyamide layer synthesized through the copolymerization of m-phenylenediamine and benzene tricarboxylic chloride. To enhance the membrane properties, silica nanoparticles were incorporated into the second layer. The experiment was designed using Design Expert software, considering three parameters: weight percentage of polyether sulfone at three levels (12%, 16%, and 20%), weight percentage of silica nanoparticles at three levels (0%, 0.1%, and 0.2%), and the process pressure at three levels (20, 25, and 30 bar). The optimal membrane configuration obtained from this experimental design consisted of a sulfone polyether polymer content of 16%, silica nanoparticles concentration of 2%, and a working pressure of 23.24 bar. Furthermore, the findings of this study suggest that the application of polymer materials and nanoparticles for membrane modification holds potential benefits for the juice industry in the future. However, it is essential to consider the wide range of factors that can influence the properties of nanocomposite membranes.

Development of Novel PET-PAN Electrospun Nanocomposite Membrane Embedded with Layered Double Hydroxides Hybrid for Efficient Wastewater Treatment.

Layered double hydroxides (LDHs) with their unique structural chemistry create opportunities to be modified with polymers, making different nanocomposites. In the current research, a novel PET-PAN embedded with Mg-AI-LDH-PVA nanocomposite membrane was fabricated through electrospinning. SEM, EDX, FTIR, XRD, and AFM were carried out to investigate the structure and morphology of the nanocomposite membrane. The characterization of the optimized nanocomposite membrane showed a beadless, smooth structure with a nanofiber diameter of 695 nm. The water contact angle and tensile strength were 16° and 1.4 Mpa, respectively, showing an increase in the hydrophilicity and stability of the nanocomposite membrane by the addition of Mg-Al-LDH-PVA. To evaluate the adsorption performance of the nanocomposite membrane, operating parameters were achieved for Cr(VI) and methyl orange at pH 2.0 and pH 4.0, respectively, including contact time, adsorbate dose, and pollutant concentration. The adsorption data of the nanocomposite membrane showed the removal of 68% and 80% for Cr(VI) and methyl orange, respectively. The process of adsorption followed a Langmuir isotherm model that fit well and pseudo-2nd order kinetics with R2 values of 0.97 and 0.99, respectively. The recycling results showed the membrane's stability for up to five cycles. The developed membrane can be used for efficient removal of pollutants from wastewater.

Development of high performance thin-film (nano) composite membranes for forward osmosis desalination applications- a review

The impact of different additives on the achievement of FO membranes was designed, reviewed, and highlighted the performances of nanocomposite over traditional membranes with evidenced literature support. This review found that the surface hydrophilicity, roughness, porosity, FO water permeation, solute retention, reverse solute permeates (RSP), and specific reverse salt permeate (SRSP) has been greatly affected by the alteration of a skin layered structure of FO membrane. The review revealed that the TFN-FO membranes showed very high surface hydrophilic properties than the TFC-FO membranes. For example, the graphene quantum dots (GODs) based UiO66-NH2 crystals (GQDs@UiO66-NH2, 250 ppm, TFN-0.25%) membrane had a goniometer (contact angle) reading of 12° which indicated a super-hydrophilic property of nanocomposite membrane over traditional TFC membranes. In addition, the TFN-FO membrane showed the highest FO permeation rate of 84.7 L m-2h−1 for the ZnO-based TFN membrane (TFN-ZnO-0.5) and a very lower RSP value of 0.005 g/L for nylon-6 (N6) substrate containing silica dioxide (SiO2) nano particle (NP) support membrane with polyamide (PA) layer nano membrane (E. Spun N6/SiO2-PA/SiO2 TFN) suggested an excellent FO performance than TFC membranes. This review also suggested that the TFN membranes provided enhanced salt rejection and FO water flux with superior fouling resistant properties which are important parameters to enhance FO performances. Hence, TFN-FO membranes can utilize as a suitable candidate for desalination applications compared to TFC membranes.

Temperature and photo sensitive PVDF-g-PNIPAAm/BN@PDA-Ag nanocomposite membranes with superior wasterwater separation and light-cleaning capabilities

Traditional water treatment membranes always face the problem of membrane contamination in the practical application. Those contaminants deposited on the membrane surface and inside the membrane pores make the filtration process more difficult. Herein, the temperature and photo sensitive nanocomposite membranes with superior wasterwater separation and light-cleaning capabilities were prepared by a non-solvent induced phase separation method, which combined the thermo-responsive property of poly(N-isopropylacrylamide) (PNIPAAm) grafted polyvinylidene fluoride (PVDF) and the high photothermal conversion character of core–shell structured BN@PDA-Ag nanosheets. The membranes can be heated to high temperature within a short period of light exposure due to the fast photothermal conversion capability of Ag and the excellent thermal conductivity of boron nitride (BN). The increase in temperature led to the contraction of PNIPAAm chains and bigger pore size. The microstructure, filtration, and cleaning performance of the nanocomposite membranes can be controlled by illumination, which allowed PVDF-g-PNIPAAm/BN@PDA-Ag membranes to achieve the effect of first interception and then cleaning. The membranes showed retention rates of 82, 99 and 95 % for BSA, oil–water emulsions and various dyes with flux recovery rates of > 90 % after light cleaning. This work provides a simpler, more efficient membrane cleaning strategy with superior potential for dealing with membrane contamination.

Polyvinyl Alcohol/Graphene Oxide Nanocomposite Membrane for Highly Efficient Oil/Water Mixture Separation

The growing amount of oily wastewater caused by frequent oil spill accidents poses a severe threat to the ecological environment. Therefore, the development of highly efficient oil/water separation methods is highly necessary. This work reports the preparation of a nanocomposite membrane using graphene oxide (GO)/polyvinyl alcohol (PVA) coated on steel meshes for oil/water mixture separation. PVA firmly anchors GO nanosheets onto the mesh surface through strong hydrogen bonds using glutaraldehyde (GA) as a crosslinker. This nanocomposite membrane exhibited superhydrophilic and underwater superoleophobic properties, with the highest oil contact angle of 158º due to its highly rough structure. The synergistic effects of GO and PVA further improved the superhydrophilicity of the prepared membrane, due to the hydrophilic nature of both GO and PVA. The separation efficiencies and water flux for a variety of oil/water mixtures were above 97.8% and 6000.0 L m−2 h−1, respectively. The prepared membrane showed excellent chemical resistance under harsh conditions without evident change in its surface wettability. Moreover, its underwater superoleophobicity was maintained after 10 cycles of abrasion testing.

High-performance electroionic artificial muscles boosted by superior ion transport with Ti3C2Tx MXene/Cellulose nanocomposites for advanced 3D-motion actuation

Low-voltage driven electro-ionic soft actuators with large deformation strain are of promising candidate for high-performance artificial muscles, with practical applications in flexible electronics, biomedical assistive devices and soft robotics. However, enhancing the actuation response and long-term stability along with excellent bending properties simultaneously still remain significant challenges. Herein, an elaborate ionically crosslinked nanocomposite membrane, assembled with 1D bacterial cellulous (BC) nanofibers and 2D Ti3C2Tx MXene nanomaterials, is reported to improve constrained ion transport for high-performance electrically activated ionic actuator. The 3D interpenetrating frameworks, arising from the synergistic effects of such combination, not only serve to enhance ion selectivity through the presence of intrinsically negatively charged functional groups but also expand the initially confined pathways, thus diminishing the energy barrier to ion transport. As a result, the integrated superior functionalities of the soft actuator exhibit large bending strain of 0.88 % with the tip displacement of 10.8 mm, ultra-stable cycling performance (>99 % retention for 5 h), and ultrabroad material response range up to 18 Hz under an ultralow voltage exertion of 0.5 V. Furthermore, the demonstration of the prototype soft actuators as actuating tracking beams of 3D-adaptive motion platform for plate deformable mirror shows their potential applications of soft robotics, thereby offering a dependable solution for driving the next generation of sophisticated intelligent systems.

Development of film nanocomposite membranes from nanocrystalline cellulose combined with reduced graphene oxide or graphene oxide: Evaluation of potential applications in proton exchange membranes

Raw materials from renewable sources are actually of interest to design materials with functional properties for use in the proton exchange membranes (PEMs) field, and thus replace the costly based-Nafion PEMs. Corncob (CC), the by-product of harvesting grains, is rich in lignocellulose polymers, which can be extracted and processed through pretreatments and hydrolysis chemical reactions to remove hemicellulose (H), lignin (L) and amorphous cellulose (C) to obtain nanocrystalline cellulose (CNC). The electrochemical, mechanical and water up-take properties of CNC can be adjusted by adding reduced graphene oxide (rGO) or graphene oxide (GO) promoting a synergistic effect among the components to increase the proton conductivity and improve the operating temperature of PEMs. This work deals with analyzing the pretreatment and acid hydrolysis (1:100 ratio, 1 h) through monitoring structural phases after the elimination of H, L and amorphous C; and the effect of temperature (50, 60 and 70 °C) to obtain CNC on crystallinity and crystal/fiber sizes is studied. The hydrolysis time (1 and 1.5 h) at 60 °C was also considered. The Results indicate the coexistence of phases I-α, I-β and II after pretreatments and the disappearance of phase II after acid hydrolysis. The increase in temperature was key inducing high crystallinity percentages (from 52% to 68%), crystallite sizes (from 2 to 4 nm) and diameter of microfiber (from 18 to 25 nm). Hybrid PEMs based on optimal CNC samples (60 °C, 1 h and 1.5 h) with GO and rGO (0.5 and 1.5 wt%) were processed via casting knife to evaluate moisture uptake as well as structural, mechanical and electrochemical performance. A shorter hydrolysis time (CNC1.0 h) induces a higher hardness value compared to CNC1.5 h; the optimal sample was found with rGO (CNC1.0 h:rGO1.5 wt%). Hydrogen bonding between GO or rGO was found to be key improving the water adsorption capacity and dimensionality at 60 °C (CNC1 h:GO 0.5 wt% and CNC1.5 h:rGO1.5 wt%). The impedance evaluated at 50, 60, 65 and 70 °C indicates a decrease with temperature. CNC1.5 h, had better impedance values more than CNC1.0 h. The greatest proton conductivity was found for CNC1.5 h:rGO 0.5 wt%. Therefore, these proposed and ecofriendly CNC:rGO and CNC:GO materials can fulfil the required properties for PEMs applications to replace Nafion membranes.

Enhanced photocatalytic properties of graphene oxide/polyvinylchloride membranes by incorporation with green prepared SnO2 and TiO2 nanocomposite for water treatment

Photocatalytic membranes (PMR) have significant potential for utilization in energy-efficient water purification and wastewater treatment. The integration of membrane filtration's physical separation with photocatalysis's organic degradation is facilitated by their respective capabilities. In the present study, a more advanced graphene oxide (GO) membrane with improved photocatalytic properties was developed. This was achieved by incorporating tin dioxide (SnO2) and titanium dioxide (TiO2) nanoparticles (NPs) into a polyvinyl chloride (PVC) matrix, resulting in the fabrication of a microfiltration flat sheet membrane. The hydrophilicity of the membrane surface was investigated. The existence of NPs on membrane surfaces was demonstrated by FESEM images, Raman spectra, and FT-IR measurements. The porosity was affected by the addition of NPs; it increased from 59 to 76, and 92 for GO/TiO2, and GO/SnO2 respectively. The relationship between photocatalysis and filtration was investigated. Each nanocomposite membrane displayed a greater water flux and removal efficiency than a blank PVC membrane. Whereas the water flux enhanced from 1.3 to 17.6, and 20.5 for GO/TiO2, and GO/SnO2 respectively. Sunlight improves water flow and rejection compared to darkness. This research provides an alternative and highly efficient photocatalytic membrane for removing organic compounds from water, as the GO/SnO2 nanocomposites membrane exhibits the highest photocatalytic degradation up to a rejection rate of 98% when compared to an unmodified membrane.

A CFD simulation and experimental study: The impact of aerator design on the bubble flow pattern, foulant removal and scouring capability of flat sheet membrane bioreactor (FSMBR)

Membrane fouling is a main drawback of membrane bioreactor systems. Moreover, optimization of influential parameters via practical analyses is tedious and time-consuming. Therefore, the CFD-RSM approach accompanied by experimental results was employed to propose the optimal aerator design. In comparison with the linear nozzles, simulation results proposed that at equal air flow rate, the angular nozzle aerators with 30° toward the surface of the membrane could provide higher amounts of surface tension, air scouring capabilities as well as air volume fraction at a similar air flow. Simulation findings were experimentally validated using a bench-scale MBR system. Obtained results showed that the irreversible fouling ratio to the total fouling ratio for neat membrane was decreased from 62.99 % to 43.97 % for linear and angular nozzles, respectively. This improvement in the nozzle performance was more pronounced for nanocomposite membranes, in which the abovementioned ratio was decreased from 43.44 % to 24.57 %. It is confirmed that the impact of nozzle design on the nanocomposite membrane was 30.48 % higher than that of the neat membrane. Specific aeration demand (SADm) value was decreased from 0.77 to the 0.49 [Nm3/(m2h)] at an equal amount of shear stress and lower inlet velocity, when linear nozzles were replaced by the angular nozzles. The lower SADm and better foulant capability leads to the optimal operation condition and lower energy as well as operating costs.

Effect of incorporation of multi-walled carbon nanotubes on the CO2/CH4 separation performance of sulfonated poly (ether ether ketone) / polyetherimide composite membranes using design of experiments and molecular dynamics simulation methods

Blend membranes were prepared based on sulfonated poly (ether ether ketone) (SPEEK) and poly (etherimide) (PEI) using different amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 wt%). PEEK has been sulfonated directly to reach 70 % degree of sulfonation. The manufactured membranes were examined by X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). The effect of the composition of SPEEK / PEI on membrane selectivity was investigated under different feed pressures (2 to 8 bar) and temperatures (25 to 55 °C). The values of selectivity and gas permeability were varied between the value of the individual polymers, fluctuating systematically with SPEEK / PEI content variation in the blends. TGA and tensile tests result obtained for prepared membranes shown that the hybrid membrane had good thermal and mechanical properties. The addition of MWCNTs to the blend led to simultaneously improve the selectivity and permeability of the pair gases of CO2 and CH4. The permeability of CO2, as well as CH4/CO2 selectivity for the membrane with the same weight of SPEEK and PEI, and 1 wt% of MWCNTs (coded SP55M1) experienced an increase of about 22 % compared with the neat membrane. Molecular dynamics simulations (MDS) were performed by employing the COMPASS force field to estimate the diffusivity of CH4 and CO2 gases through selected membranes. At last, with compared to the obtained experimetal data, the optimized nanocomposite membrane, integrated with MWCNTs was efficient, which makes it promising platform to separate mixed gase flows of CO2 and CH4 and other related environmental processes.

Performance evaluation and efficiency of functionalized cellulose nanocomposites for the removal of pharmaceutical contaminants from the aqueous environment

Water pollution caused by pharmaceuticals has raised many concerns about the potential risks to human health and living organisms. Therefore, it is important to develop a high-efficiency adsorbent for the removal of organic pollutants from wastewater. Cellulose-based nanomaterials can be effectively used for wastewater treatment. In the present work, new nanocomposites are designed through the functionalization of cellulose with β-cyclodextrin (β-CD/Cell), cucurbit [6] (CUR/Cell), and calixarene (CAL/Cell) groups with Tetrafluoroterephthalonitrile (TFP) linker. Then, the adsorption of pharmaceutical agents such as propranolol (PRO), levofloxacin (LEV), and metformin (MET) is examined on nanocomposites as efficient adsorbents. The obtained results show that the systems containing the β-CD functional group have a higher adsorption for all three types of drugs compared to the other two nanocomposites. It should be noted that both types of interactions (Van der Waals and electrostatic) between β-CD/Cell and CAL/Cell nanocomposites with micropollutant molecules are significant, whereas, between CUR/Cell and drugs, the electrostatic interaction is dominant. Also, the most number of hydrogen bonds exist between the MET drug and nanocomposite membranes, which leads to stronger electrostatic interactions. In addition, our findings confirm that the system containing β-CD/Cell nanocomposite and LEV drug has the highest number of contacts (2300) at the beginning of the simulation and the most interaction energy (368.5 kJ/mol). It is worth mentioning that the negative values of the interaction energies show that all of the investigated drug molecules exothermically and spontaneously adsorbed on the surface of cellulose nanocomposites.

Antibacterial adsorptive membrane decorated via silver nanolayer for ammonia removal

The presence of ammonia pollution in surface water warrants a rigorous examination due to its tendency to surpass established regulatory thresholds, particularly in several global river systems. Numerous traditional techniques have been extensively used for the elimination of ammonia; nevertheless, their efficacy in ammonia removal is not deemed remarkable. The use of membrane technology is increasingly being employed to eliminate nitrogen compounds from water and wastewater. Nevertheless, it is crucial to acknowledge the limited body of literature pertaining to the use of nanomaterials to eradicate multiple pollutants. Specifically, there is a notable scarcity of studies investigating the simultaneous eradication of both bacteria and ammonium. This work included the fabrication of a PES-PVP flat sheet membrane that featured an adsorbent material, namely a silver (Ag) nanolayer. The objective was to investigate the effectiveness of this membrane in removing ammonia as well as its potential antifouling and antibacterial properties. The PES-PVP/Ag nanocomposite membrane underwent characterization by several spectroscopic and microscopic analytical techniques. We not only showed that the PES-PVP/Ag nanocomposite membrane has a superior 96% ammonia removal efficiency but also discussed the antibacterial mechanism against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli in order to better understand the interaction of PES-PVP/Ag nanocomposite membrane with bacteria. Moreover, as compared to the PES-PVP membrane, the PES-PVP/Ag nanocomposite membrane exhibited enhanced antifouling capabilities. The PES-PVP/Ag nanocomposite membrane appears as a very promising method for the treatment of advanced antimicrobial or ammonia-contaminated water due to the ease of separation, plentiful availability, as well as the extremely strong antifouling and antibacterial activity displayed by the membrane.

High perm-selectivity and performance of tuned nanofiltration membranes by merging carbon nitride derivatives as interphase layer for efficient water treatment

The support characteristics under polyamide thin films have proven significant impact on the performance of nanofiltration thin film composite (TFC) membranes. In this study, polyethersulphone (PES) support was initially furnished with an interphase layer of different graphitic carbon nitride derivatives and nanocomposites (g-C3N4, oxidized g-C3N4, and g-C3N4/CuFe2O4) to improve the specifications of TFC membranes. Then, the polyamide layer was fabricated by interfacial polymerization on top of the interphase layer. The interlayer helped fine-tune the thickness and surface characteristics such as roughness, wettability, and zeta potential of the polyamide layer, in the way of improving the separation and antifouling capabilities of the TFC membranes. The interlayered thin film nanocomposite (ITFN) membranes considerably indicated better water permeability and rejection of methylene blue (MB), methyl orange (MO), Cadmium nitrate, and sodium sulfate (Na2SO4). We showed that ITFNs loaded with 0.01 wt% g-C3N4/CuFe2O4 had a permeability of ~9.2 LMH/bar, upper from ~3.8 LMH/bar in the pristine form, exhibiting outstanding water flux. The rejection data showed nearly two-fold increase of rejection of Cadmium nitrate, sodium sulfate, and dyes rather than the pristine nanofiltration membrane. The modified nanofiltration membranes remarkably exhibited better antifouling properties and higher flux recovery ratios as well.

Fabrication of an electrically conductive separation layer with stable nanonetworks for efficient removal of heavy metals under an external voltage

Positively charged nanofiltration membrane shows great potentials in removing heavy metal ions from wastewater, but excellent separation and antifouling properties remain a challenge. Herein, a novel nanocomposite membrane with a dual-charged electrically conductive separation layer was fabricated by combining phase inversion, vacuum filtration and chemical crosslinking. The microstructure of PSF/sodium styrene-maleic anhydride copolymer (SMANa) composite membranes was systematically manipulated by adjusting the intermolecular binding state of SMA. Subsequently, various deposition layers were generated on the membrane surface by tuning the CNT/rGO ratios, and polyethylenimine (PEI) was also introduced by crosslinking with tannic acid (TA). The optimized membrane possessed a dual-charged separation layer with excellent conductivity and stable three-dimensional (3D) nanonetworks, and acted as cathode to achieve outstanding rejections of Cu2+(92.9%), Ni2+ (99.0%), Pb2+ (99.9%) and Cd2+ (99.5%) at a -3V voltage, with the permeate fluxes of 14.4～18.6 L/m2 h bar. This is ascribed to the synergistic effect among the electroreduction of metal ions, the chemical reaction with OH− to form hydroxides, the chelation with –OH and –NH2 groups, and the adsorption-induced electrostatic repulsion. Importantly, it also displayed superior stability over multiple runs and outstanding antifouling performances owing to the superposition of electrochemistry effect and stable hydration layers.

Polyvinyl chloride grounded cobalt molybdophosphate nanocomposite membrane: comparative study of fixed charge density

Polyvinyl chloride grounded cobalt molybdophosphate nanocomposite membrane: comparative study of fixed charge density

Fabrication and characterization of hydrophobic/hydrophilic dual-layer polyphenyl sulfone Janus membrane for application in direct contact membrane distillation

In this study, single-layer (SL) and dual-layer (DL) polyphenyl sulfone (PPSU) flat sheet nanocomposite Janus membranes were fabricated via a combination of VIPS and NIPS techniques for direct contact membrane distillation (DCMD) for the first time. Hydrophobic silica nanoparticles (SiNP-B) were incorporated into the SL membranes and the top layer of the DL membranes, while hydrophilic silica nanoparticles (SiNP-L) were added into the down layer of the DL membranes. The effect of the SiNP-B concentration (1–5 wt%) and the top layer thickness (50 and 100 μm) on the morphology, mean pore size (MPS), thickness, porosity, surface roughness, water contact angle (WCA), liquid entry pressure, mechanical strength, and thermal conductivity were investigated. All of the membranes showed a finger-like structure surrounded by a sponge-like structure. The membranes were examined in the DCMD of a 35,000 ppm saline solution at different feed temperatures (50–70 °C) and flow rates (250–1000 mL/min). The DL membranes possessed higher fluxes than the SL membranes through increasing MPS and WCA. The DL membrane with a SiNP-B concentration of 2 wt% and a hydrophobic thickness of 50 μm (DL- 2,50) achieved the highest flux (42.68 ± 0.35 kg/m2h) and salt rejection (94.90 %) during 5 h. This membrane has an MPS of 0.22 ± 0.03 μm, a thickness of 201 ± 4 μm, and a porosity of 76 ± 2 %. It could be concluded the proper pore size distribution is the most important factor in achieving a successful DCMD operation.