Polyacrylonitrile Nanofiber Membrane Research Articles

High-temperature piezoelectric conversion using thermally stabilized electrospun polyacrylonitrile membranes

Electrospun polyacrylonitrile nanofiber membranes show high flexibility and excellent piezoelectric properties after thermal stabilization and can be used to harvest energy in a broad temperature range from room temperature to 550 °C.

Removal of dye waste by weak cation-exchange nanofiber membrane immobilized with waste egg white proteins

In this research, a protein nanofiber membrane (P-COOH-CEW) was developed to treat the dye waste. Initially, polyacrylonitrile nanofiber membrane (PAN) was prepared by electrospinning, followed by heat treatment, alkaline treatment, and neutralization to obtain weak cation exchange nanofiber membrane (P-COOH). The P-COOH membrane was chemically coated with chicken egg white (CEW) proteins to obtain a 3D structure of complex protein nanofiber membrane (P-COOH-CEW). The composite prepared was characterized with Fourier Transform Infrared analysis (FTIR), Scanning Electron Microscopy (SEM), and thermogravimetric analysis (TGA). Further, the composite was evaluated by investigating the removal of Toluidine Blue O (TBO) from aqueous solutions in batch conditions. Different operating parameters - coupling of CEW, shaking rate, initial pH, contact time, temperature, and dye concentration were studied. From the results, maximum removal capacity and equilibrium association constant was determined to be 546.24 mg/g and 10.18 mg/mg, respectively at pH 10 and 298 K. The experimental data were well fitted to pseudo-second order model. Furthermore, desorption studies revealed that the adsorbed TBO can be completely eluted by using 50% ethanol or 50% glycerol in 1 M NaCl solution. Additionally, the reuse of P-COOH-CEW membrane reported to have 97.32% of removal efficiency after five consecutive adsorption/desorption cycles.

Polyacrylonitrile Nanofiber Membrane Modified with Ag/GO Composite for Water Purification System.

Silver nanoparticle-modified graphene oxide (Ag/GO) was reliably prepared by using sodium borohydride (NaBH4) in the presence of citric acid capping agent via a simple wet chemistry method. This rapidly formed Ag/GO composite exhibited good dispersity in a solution containing hydrophilic polyacrylonitrile (PAN). Subsequent electrospinning of this precursor solution resulted in the successful formation of nanofibers without any notable defects. The Ag/GO-incorporated PAN nanofibers showed thinner fiber strands (544 ± 82 nm) compared to those of GO-PAN (688 ± 177 nm) and bare-PAN (656 ± 59 nm). Subsequent thermal treatment of nanofibers resulted in the preparation of thin membranes to possess the desired pore property and outstanding wettability. The Ag/GO-PAN nanofiber membrane also showed 30% higher water flux value (390 LMH) than that of bare-PAN (300 LMH) for possible microfiltration (MF) application. In addition, the resulting Ag/GO-PAN nanofiber membrane exhibited antibacterial activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). Furthermore, this composite membrane exhibited outstanding anti-fouling property compared to the GO-PAN nanofiber membrane in the wastewater treatment. Therefore, the simple modification strategy allows for the effective formation of Ag/GO composite as a filler that can be reliably incorporated into polymer nanofiber membranes to possess improved overall properties for wastewater treatment applications.

Highly efficient dye removal and lysozyme purification using strong and weak cation-exchange nanofiber membranes

Electrospinning technology was applied for the preparation of polyacrylonitrile (PAN) nanofiber membrane in this work. After hot pressing, alkaline hydrolysis and neutralization treatment, a weak acid cation exchange membrane (P-COOH) was prepared. By the covalent coupling reaction between the acidic membrane and aminomethane sulfonic acid (AMSA), a strong acidic nanofiber membrane (P-SO3H) was obtained. The surface morphology, chemical structure, and thermal stability of the prepared ion exchange membranes were analyzed via SEM, FTIR and TGA. Analytical results showed that the membranes were prepared successfully and thermally stable. The ion exchange membrane (IEX) was conducted with the newly designed membrane reactor, and different operating conditions affecting the adsorption efficiency of Toluidine Blue dye (TBO) were investigated by dynamic flow process. The results showed that dynamic binding capacity (DBC) of weak and strong IEX membranes for TBO dye was ~170 mg/g in a dynamic flow process. Simultaneously, the ion exchange membranes were also used for purifying lysozyme from chicken egg white (CEW). Results illustrated that the recovery yield and purification factor of lysozyme were 93.43% and 29.23 times (P-COOH); 90.72% and 36.22 times (P-SO3H), respectively. It was revealed that two type ion exchange membranes were very suitable as an adsorber for use in dye waste treatment and lysozyme purification process. P-SO3H strong ion-exchange membrane was more effective either removal of TBO dye or purification of lysozyme. The ion exchange membranes not only effectively purified lysozyme from CEW solution, but also effectively removed dye from wastewater.

Egg white lysozyme purification by a stirred cell contactor equipped with a weak ion-exchange nanofiber membrane: Process development and scale-up

A weak ion-exchange membrane (P-COOH) was synthesized by alkaline hydrolysis of a polyacrylonitrile nanofiber membrane prepared by electrospinning process. The P-COOH membrane was characterized for its physical properties and its application for purification of lysozyme from chicken egg white was investigated. The lysozyme adsorption efficiency of the P-COOH membrane operating in a stirred cell contactor (Millipore, Model 8010) was evaluated. The effects of key parameters such as the feed concentration, the rotating speed, the flow rate of feed and the operating pressure were studied. The results showed successful purification of lysozyme with a high recovery yield of 98% and a purification factor of 63 in a single step. The purification strategy was scaled-up to the higher feedstock loading volume of 32.7 and 70 mL using stirred cell contactors of Model 8050 and 8200, respectively. The scale-up processes achieved similar purification results, proving linear scalability of the purification technique adopted.

Removal of cationic dye waste by nanofiber membrane immobilized with waste proteins

Water pollution caused by dyes has been a serious problem affecting human health and environment. The surface of polyacrylonitrile (PAN) nanofiber membranes was modified by mild hydrolysis and coupled with bovine serum albumin (BSA) obtained from the laboratory wastes, resulting in the synthesis of P-COOH and P-COOH-BSA nanofibers. The nanofibers with specific functional groups may enhance their potential applications toward the removal of ionic dyes in wastewater. Toluidine blue O (TBO) was applied as an example of cationic dye to evaluate the removal efficiency of P-COOH-BSA nanofiber. Results showed that the equilibrium dissociation constant and maximum removal capacity were 0.48 mg/mL and 434.78 mg/g, respectively, at pH 12, where the TBO removal can be explained based on Langmuir isotherm and pseudo-second-order model. Desorption studies have shown that TBO adsorbed on P-COOH-BSA protein membrane can be completely eluted with either 1 M NaCl or 50% glycerol. The results of repeated studies indicated that after five consecutive adsorption/desorption cycles, the removal efficiency of TBO can be maintained at ~97%. P-COOH-BSA has shown to be promising adsorbent in TBO dye removal from dye wastewater.

Sol–Gel SiO2 on electrospun polyacrylonitrile nanofiber for efficient oil-in-water emulsion separation

A membrane for efficient oil-in-water emulsion separation requires a surface with hydrophilic/underwater oleophobic properties. In this study, a simple and facile sol–gel strategy was proposed for preparing oil-in-water emulsion separation membrane with hydrophilic/underwater oleophobic surface by growing amorphous SiO2 sheets on an electrospun polyacrylonitrile nanofiber membrane (PAN NFM). The composite membranes (PAN@SiO2 NFMs) showed excellent properties in mechanical strength, hierarchical microporous structure, hydrophilicity and underwater oleophobicity, as well as remarkable performance in water flux, separation efficiency and cyclic stability. Under a low pressure of 1 kPa driven by the self-weight of emulsion, the PAN@SiO2 NFM demonstrated a large flux of 3994.3 ± 356.0 L m−2 h−1 and a high separation efficiency of 99.50%. In ten successive cycle tests, fluxes of the PAN@SiO2 NFM remained above 3000 L m−2 h−1, while the residual TOC in filtrate was stable at around 30 mg L−1, indicating the PAN@SiO2 NFM has excellent cyclic stability. It is also demonstrated that the PAN@SiO2 NFM is suitable for the separation of various kinds of emulsions, such as toluene, n-heptane, paraffin liquid, n-hexane and xylene. Hence, the prepared PAN@SiO2 NFM is a promising hydrophilic/underwater oleophobic membrane for efficient emulsion separation.

Mixed Dye Removal Efficiency of Electrospun Polyacrylonitrile-Graphene Oxide Composite Membranes.

Exfoliated graphene oxide (GO) was reliably modified with a cetyltrimethylammonium chloride (CTAC) surfactant to greatly improve the dispersity of the GO in a polyacrylonitrile (PAN) polymer precursor solution. Subsequent electrospinning of the mixture readily resulted in the formation of GO–PAN composite nanofibers containing up to 30 wt % of GO as a filler without notable defects. The absence of common electrospinning problems associated with clogging and phase separation indicated the systematic and uniform integration of the GO within the PAN nanofibers beyond the typical limits. After thoroughly examining the formation and maximum loading efficiency of the modified GO in the PAN nanofibers, the resulting composite nanofibers were thermally treated to form membrane-type sheets. The wettability and pore properties of the composite membranes were notably improved with respect to the pristine PAN nanofiber membrane, possibly due to the reinforcing filler effect. In addition, the more GO loaded into the PAN nanofiber membranes, the higher the removal ability of the methylene blue (MB) and methyl red (MR) dyes in the aqueous system. The adsorption kinetics of a mixed dye solution were also monitored to understand how these MB and MR dyes interact differently with the composite nanofiber membranes. The simple surface modification of the fillers greatly facilitated the integration efficiency and improved the ability to control the overall physical properties of the nanofiber-based membranes, which highly impacted the removal performance of various dyes from water.

Polyacrylonitrile Nanofiber Membranes Modified with Ni-Based Conductive Metal Organic Frameworks for Air Filtration and Respiration Monitoring

We developed a nanofiber membrane that blocks particulate matters (PMs) and monitors respiration. The membrane was composed of polyacrylonitrile (PAN) nanofibers and was prepared by electrospinning...

A high flux graphene oxide nanoparticles embedded in PAN nanofiber microfiltration membrane for water treatment applications with improved anti-fouling performance

A high flux and anti-fouling graphene oxide (GO) nanoparticles embedded in polyacrylonitrile (PAN) nanofiber microfiltration membranes (PANGMs) were fabricated through the facile electrospinning method and were characterized by water treatment applications. The synthesized GO nanoparticles and GO nanoparticles embedded in PAN nanofiber membranes were characterized by FESEM, FTIR, and EDS. SEM images showed that the PANGMs possessed randomly overlaid fibers with a network-like highly porous structure similar to the pristine PAN nanofiber membrane, while agglomeration of GO nanoparticles was observed at high GO concentration. The introduction of GO nanoparticles into the PAN polymeric matrix significantly increased the permeation flux of the resulting membrane in both dead-end and cross-flow filtration systems. A high flux recovery ratio of 96.6% and a low irreversible fouling ratio of 3.4% were obtained at 2% (wt.) GO nanoparticles. More importantly, a high flux recovery ratio of GO nanoparticles embedded in PAN nanofiber membrane was retained after 20 repeated cycles of activated sludge suspension filtration. Therefore, it can speculate that the incorporation of GO nanoparticles into the PAN nanofibers could efficiently improve the anti-fouling ability of membranes which had opened up an alternative for the preparation of high flux and anti-fouling microfiltration membranes in practical water treatment applications such as membrane bioreactors.

Evaluation of dynamic binding performance of C-phycocyanin and allophycocyanin in Spirulina platensis algae by aminated polyacrylonitrile nanofiber membrane

Polyacrylonitrile nanofibrous membrane (PAN) was prepared by electrospinning technique and was directly converted to polyamine membrane by 50 % and 100 % (w/w) ethylenediamine (EDA) and hexamethylenediamine (HDA), respectively. The aminated PAN nanofiber membrane equipped with protein liquid chromatography were used to evaluate the dynamic binding capacity for C-phycocyanin (CPC) and allophycocyanin (APC) from disrupted Spirulina platensis under different operating conditions. Experimental results showed that the contaminating proteins were completely removed during the flow and wash procedures. However, a large amount of APC and CPC can be retained on the membranes. Consequently, the aminated PAN membrane may have a high potential for use in the separation of APC/CPC and TP from a complex algae feedstock. In this study, a highly effective capture of APC/CPC can be achieved in one-step membrane chromatography, which can be directly employed as an antibacterial and antioxidant nanofiber membranes.

Heavy metal elimination based on metal organic framework highly loaded on flexible nanofibers

Efficient adsorbents for removal heavy metals are extensively urgent in modern society. Metal-organic frameworks (MOFs) with abundant porosity and tunable structure make it potential to access the advantages of high permeability and adsorbability in water pollutant control. However, MOFs nanoparticles inconvenient to recycle in solution hinder its application in water pollutant treatment. Herein, we report an in-situ growth and large-scalable manufacturing method to fabricate ZIF-8 nanoparticles on electrospun polyacrylonitrile (PAN) nanofibers membrane (ZIF-8/PAN NF) by hot pressing. Consequently, the prepared ZIF-8/PAN NF possesses high loading, uniform dispersion and large-scalable area as well as good flexibility. The fabricated ZIF-8/PAN NF exhibits excellent performance with fast flux (12,000 L/(m2h)) and high filtration efficiency (96.5%) for Cu2+ in dynamic adsorption. Additionally, adsorption and electrochemistry are introduced simultaneously. The Cu2+ removal rate of ZIF-8/PAN NF reaches 34.1% in 4 min with combination of adsorption and electrochemistry. While it is 29.2% for Cu2+ elimination in adsorption. Given the outstanding performance and easy manufacture, this study might bring MOFs powder to eliminate water pollution into practical application.

Effective purification of lysozyme from chicken egg white by tris(hydroxymethyl)aminomethane affinity nanofiber membrane

Polyacrylonitrile nanofiber membrane functionalized with tris(hydroxymethyl)aminomethane (P-Tris) was used in affinity membrane chromatography for lysozyme adsorption. The effects of pH and protein concentration on lysozyme adsorption were investigated. Based on Langmuir model, the adsorption capacity of P-Tris nanofiber membrane was estimated to be 345.83 mg/g. For the operation of dynamic membrane chromatography with three-layer P-Tris nanofiber membranes, the optimal operating conditions were at pH 9, 1.0 mL/min of feed flow rate, and 2 mg/mL of feed concentration. Chicken egg white (CEW) was applied as the crude feedstock of lysozyme in the optimized dynamic membrane chromatography. The percent recovery and purification factor of lysozyme obtained from the chromatography were 93.28% and 103.98 folds, respectively. Our findings demonstrated the effectiveness of P-Tris affinity nanofiber membrane for the recovery of lysozyme from complex CEW solution.

Free-standing flexible graphene-based aerogel film with high energy density as an electrode for supercapacitors

Abstract Two-dimensional graphene film exhibits sluggish ion diffusivity while three-dimensional (3D) graphene aerogel has low packing density and poor mechanical flexibility. Consequently, there is an urgent need for graphene-based film with both mechanical robustness and high specific capacitance. Here, we present an easy and scalable strategy for fabricating a free-standing flexible graphene-based aerogel film electrode with a two-layered structure, in which the top layer is an interconnected macroporous reduced graphene oxide/carbon nanotube (RGO/CNT) aerogel, and the bottom layer is a flexible electrospun polyacrylonitrile (PAN) nanofiber membrane. The porous 3D structure of the aerogel provides fast transport of electrolyte ions and electrons, while the nanofiber membrane provides both strong support for the aerogel and mechanical flexibility. Polypyrrole (PPy) can be uniformly loaded on RGO/CNT/PAN (RCP) composite aerogel film to provide pseudocapacitance, and nitrogen-doped RGO/CNT/carbon nanofiber (NRCC) aerogel film can be obtained by further pyrolysis. The resultant RCP@PPy-0.05//NRCC based asymmetric supercapacitor can have a maximum voltage of 1.7 V and a maximum energy density of 60.6 W h kg−1 at 850.2 W kg−1. This indicates that free-standing graphene-based aerogel film can be used in flexible supercapacitors.

Antibacterial efficacy of chitosan- and poly(hexamethylene biguanide)-immobilized nanofiber membrane

In this study, polyacrylonitrile (PAN) nanofiber membrane was prepared by an electrospinning technique. After alkaline hydrolysis, the ion-exchange nanofiber membrane (P-COOH) was grafted with chitosan molecules to form a chitosan-modified nanofiber membrane (P-COOH-CS). Poly(hexamethylene biguanide) (PHMB) was then covalently immobilized on P-COOH and P-COOH-CS to form P-COOH-PHMB and P-COOH-CS-PHMB, respectively. The nanofiber membranes were subjected to various surface analyses as well as to the evaluations of antibacterial activity against Escherichia coli. The optimal modification conditions for P-COOH-CS-PHMB were attained by water-soluble chitosan at 50 kDa of molecular weight, coupling pH at 7, and 0.05% (w/w) of PHMB. Within 10 min of treatment, the antibacterial rate was close to 100%. Under the similar conditions of antibacterial treatment, the P-COOH-CS-PHMB exhibited a better antibacterial efficacy than the P-COOH-PHMB. When the number of bacterial cells was increased by 2000 folds, both types of nanofiber membranes still maintained the antibacterial rate close to 100%. After five cycles of repeated antibacterial treatment, the antibacterial efficacy of P-COOH-PHMB was 96%, which was higher than that of P-COOH-CS-PHMB (83%). The experimental results revealed that the PHMB-modified nanofiber membranes can be suitably applied in water treatment such as water disinfection and biofouling control.

Carbonization of electrospun polyacrylonitrile (PAN)/cellulose nanofibril (CNF) hybrid membranes and its mechanism

Polyacrylonitrile (PAN)/cellulose nanofibril (CNF) based carbon nanofiber membranes were produced by electrospinning and carbonization method, in which the CNF amount was 1 wt%. In order to control the spinning process, the rheological properties of the PAN/CNF suspensions were measured before electrospinning. In addition, the effects of CNF particle size on the structure and properties of carbon nanofiber membranes were investigated systematically by SEM, FTIR and mechanical test. Meanwhile, the reaction mechanism of PAN and PAN/CNF nanofiber membranes in the process of stabilization and carbonization was also fully discussed. The results show that the addition of CNFs can improve the breaking strength and conductivity of PAN carbon nanofiber membrane. Moreover, CNFs also can accelerate the carbonization rate and reduce the reaction conditions of PAN nanofiber membranes. Therefore, CNFs are effective enhancers for PAN based carbon nanofiber membranes.

A 3D polyacrylonitrile nanofiber and flexible polydimethylsiloxane macromolecule combined all-solid-state composite electrolyte for efficient lithium metal batteries.

All-solid-state polymer electrolytes have received widespread attention due to their superior safety over liquid electrolytes that are prone to leaks. However, poor ionic conductivity and uncontrollable lithium dendrite growth have greatly limited the rapid development of polymer electrolytes. Hence, we report a composite polymer electrolyte combining a polyacrylonitrile (PAN) electrospun fiber membrane, flexible polydimethylsiloxane (PDMS) macromolecules and a polyethylene oxide (PEO) polymer. The introduction of PDMS with a highly flexible molecular chain, ultra-low glass transition energy and high free volume can help optimize lithium ion migration paths and improve the interface compatibility between the electrolyte and the electrode. In addition, the nano-network structure of the PAN nanofiber membrane can promote the interaction between adjacent polymer molecular chains and improve the mechanical properties of the composite electrolyte to suppress the lithium dendrite growth. The synergistic effect of the PDMS and PAN electrospun nanofiber membranes endows the composite electrolyte with superior ionic conductivity and excellent electrochemical stability towards lithium metal. The interface impedance of the Li/Li symmetric battery with the composite electrolyte after 15 days of continuous standing has no significant change compared with the initial state, and the battery can maintain stable cycling for 1200 h without short circuit under a dynamic current of 0.3 mA cm-2. The obtained composite polymer electrolyte has potential application prospects in the field of high-energy lithium metal batteries.

Construction of superhydrophilic hierarchical polyacrylonitrile nanofiber membranes by in situ asymmetry engineering for unprecedently ultrafast oil–water emulsion separation

With multi-hydrophilic functional networks, asymmetric PAN nanofiber membranes with finely tailored pore structures and hydrophilicity are constructed and show high permeance 22 000 L m−2 h−1 bar−1, separation efficiency 99.2% and flux recovery rate 98%.

Composites Based on Nanoparticle and Pan Electrospun Nanofiber Membranes for Air Filtration and Bacterial Removal.

Often, solid matter is separated from particle-laden flow streams using electrospun filters due to their high specific surface area, good ability to capture aerial particulate matter, and low material costs. Moreover, electrospinning allows incorporating nanoparticles to improve the filter’s air filtration efficiency and bacterial removal. Therefore, a new, improved polyacrylonitrile (PAN) nanofibers membrane that could be used to remove air pollutants and also with antibacterial activity was developed. We engineered three different filters that are characterized by the different particles embedded in the PAN nanofibers: titanium dioxide (TiO2), zinc oxide (ZnO), and silver (Ag). Then, their filtration performance was assessed by quantifying the filtration of sodium chloride (NaCl) aerosol particles of 9 to 300 nm in diameter using a scanning mobility particle sizer. The TiO2_F filter displayed the smallest fiber diameter and the highest filtration efficiency (≈100%). Conversely, the Ag_F filter showed the highest quality factor (≈0.06 Pa−1) because of the lower air pressure drop. The resulting Ag_F nanofibers displayed a very good antibacterial activity using an Escherichia coli suspension (108 CFU/mL). Moreover, the quality factor of these membranes was higher than that of the commercially available nanofiber membrane for air filtration.

Stabilization of Li-Se Batteries by Wearing PAN Protective Clothing.

Lithium-selenium (Li-Se) batteries have recently attracted more and more attentions as new secondary battery systems due to the similarity but better performances than lithium-sulfur (Li-S) batteries. However, the dissolution of selenium in electrolytes results in low selenium utilization, concentration polarization, inferior capacities, and unstable cycling performances. Herein, 46.58 wt% of selenium is loaded on carbon cloths through the calcination process, which were directly used as self-supporting cathodes. Carbonized polyacrylonitrile (PAN) nanofiber membranes produced by electrospinning are worn as the protective clothing between the cathode and separator to avoid the loss and dissolution of selenium. The stabilization of Li-Se batteries was enhanced by introducing two interlayers, as expected, they exhibit a stable reversible average capacity of 590 mA h g-1 during 1000 cycles at a current density of 0.5 C (1 C = 675 mA g-1). No polyselenide formation is found during charging/discharging, and the effects of the introduced PAN interlayers on improving the stability and reducing the polarization of the assembled Li-Se batteries are confirmed by mechanistic characterizations. These regulated Li-Se batteries present great application potential in the future, and the design idea can also be promoted to explore other energy storage systems.