Enhancement of heavy metal ion adsorption using electrospun polyacrylonitrile nanofibers loaded with ZnO nanoparticles

Preparation of antibacterial composite film based on arginine-modified chitosan and its application in the preservation of ready-to-eat sea cucumber

An edible composite film was developed and applied for ready-to-eat sea cucumber storage to improve the product quality. The PAC film base is first prepared by mixing 0.5 % glycerin (GL) with 4 % polyvinyl alcohol (PVA) and 1 % arginine-modified chitosan (Arg-CTS) in the same volume. After the addition of nano-ZnO (ZnO) and thymol (Thy) to the PAC film base, the mechanical properties and functions were tested. Compared to the PAC film, the PAC-ZnO-ThyH composite film showed a 1.34-fold increase in the DPPH scavenging rate and a 2.19-fold increase in the ABTS scavenging rate. Contrary to the PAC film, the inhibition zone diameter of Escherichia coli and Staphylococcus aureus significantly increased by 2.35 and 4.08 folds in the PAC-Zno-ThyH film, respectively. After applying the PAC-ZnO-ThyH film to store ready-to-eat sea cucumber for 10 days, there was a significant reduction in weight loss, total volatile basic nitrogen (TVB-N), and lipid oxidation levels to 1.47 and 1.26 folds to the Ctrl group. After preservation, the hardness and chewiness of ready-to-eat sea cucumber were maintained at 1079.62 ± 138.86 N and 913.73 ± 175.79 N, respectively. The novel PAC-ZnO-ThyH composite film can be used as an active food packaging for promising seafood applications.

Electrospun Materials Based on Polymer and Biopolymer Blends-A Review

This review covers recent developments and progress in polymer and biopolymer blending and material preparation by electrospinning. Electrospinning is a technique that is used to produce nanofibers to improve the quality of membranes. Electrospun nanofibers are highly applicable in biomedical sciences, supercapacitors, and in water treatment following metal ion adsorption. The key affecting factors of electrospinning have been checked in the literature to obtain optimal conditions of the electrospinning process. Future research directions and outlooks have been suggested to think about innovative ideas for research in this field.

The Effect of Acetylene Carbon Black (ACB) Loaded on Polyacrylonitrile (PAN) Nanofiber Membrane Electrolyte for DSSC Applications

Nanofiber membranes are starting to be used as an electrolyte storage medium because of their high porosity, which causes ionic conductivity, producing high energy. The ability of nanofiber membranes to absorb electrolytes proves their stability when used for a long time. In this study, the loading of acetylene carbon black (ACB) on polyacrylonitrile (PAN) is made by the electrospun method, which in turn is applied as an electrolyte medium in DSSC. Materials characterization was carried out through FTIR to determine the functional groups formed and SEM to observe morphology and diameter distribution. Furthermore, for DSSC performance, efficiency and EIS tests were carried out. The optimum nanofiber membrane was shown by esPACB1, with the highest efficiency reaching 1.92% with a porosity of 73.43%, nanofiber diameter of 172.9 ± 2.2 nm, an absorbance of 1850, and an electron lifetime of 0.003 ms.

Research Progress of Water Treatment Technology Based on Nanofiber Membranes

In the field of water purification, membrane separation technology plays a significant role. Electrospinning has emerged as a primary method to produce nanofiber membranes due to its straightforward, low cost, functional diversity, and process controllability. It is possible to flexibly control the structural characteristics of electrospun nanofiber membranes as well as carry out various membrane material combinations to make full use of their various properties, including high porosity, high selectivity, and microporous permeability to obtain high-performance water treatment membranes. These water separation membranes can satisfy the fast and efficient purification requirements in different water purification applications due to their high filtration efficiency. The current research on water treatment membranes is still focused on creating high-permeability membranes with outstanding selectivity, remarkable antifouling performance, superior physical and chemical performance, and long-term stability. This paper reviewed the preparation methods and properties of electrospun nanofiber membranes for water treatment in various fields, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, and other special applications. Lastly, various antifouling technologies and research progress of water treatment membranes were discussed, and the future development direction of electrospun nanofiber membranes for water treatment was also presented.

A Review on Polyacrylonitrile as an Effective and Economic Constituent of Adsorbents for Wastewater Treatment

Water gets polluted due to the dumping of untreated industrial waste into bodies of water, particularly those containing heavy metals and dyes. Industrial water contains both inorganic and organic wastes. Numerous adsorbents that are inexpensive and easily available can be used to address the issue of water deterioration. This review report is focused on polyacrylonitrile as an efficient constituent of adsorbents to extract toxic ions and dyes. It discusses the various formulations of polyacrylonitrile, such as ion exchange resins, chelating resins, fibers, membranes, and hydrogels, synthesized through different polymerization methods, such as suspension polymerization, electrospinning, grafting, redox, and emulsion polymerization. Moreover, regeneration of adsorbent and heavy metal ions makes the adsorption process more cost-effective and efficient. The literature reporting successful regeneration of the adsorbent is included. The factors affecting the performance and outcomes of the adsorption process are also discussed.

Removal of Cr(VI) from aqueous solution by a novel ZnO-sludge biochar composite

The incorporation of ZnO into biochar has become a promising way to obtain adsorbents with enhanced adsorption capacity. In this study, a low-cost ZnO-sludge biochar composite (ZBC) was prepared by a simply in situ method using sewage sludge biochar (SBC) and zinc acetate, as well as employed for Cr(VI) adsorption in water. The results of XPS and FT-IR suggested that the ZBC surface had more functional groups such as -COOH, -OH, -C-O, ZnO, etc. Compared with SBC, the BET-specific surface area of the ZBC increased from 8.82 to 41.24 m²·g^-1, which provides potential advantages for Cr(VI) uptake. Benefiting from ZnO incorporation, about an 18% increase in Cr(VI) removal efficiency was obtained. The maximum removal efficiency and equilibrium adsorption amount of ZBC for Cr(VI) reached 98.4% and 33.87 mg·g^-1, respectively. The adsorption was spontaneous and endothermic nature, and coincided nicely with pseudo-second-order kinetics and Langmuir isotherm. The analyses indicated that Cr(VI) removal by ZBC was predominantly via electrostatic attraction, surface complexation, ion exchange, and reduction. This study provided valuable insights into the problem of sludge disposal and provided a new and effective method for Cr(VI) removal.

Ag nanoparticles immobilized sulfonated polyethersulfone/polyethersulfone electrospun nanofiber membrane for the removal of heavy metals

In this work, Eucommia ulmoides leaf extract (EUOLstabilized silver nanoparticles (EUOL@AgNPs) incorporated sulfonated polyether sulfone (SPES)/polyethersulfone (PES) electrospun nanofiber membranes (SP ENMs) were prepared by electrospinning, and they were studied for the removal of lead (Pb(II)) and cadmium (Cd(II)) ions from aqueous solutions. The SP ENMs with various EUOL@AgNPs loadings were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscope, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and contact angle (CA) measurements. The adsorption studies showed that the adsorption of Cd(II) and Pb(II) was rapid, achieved equilibrium within 40 min and 60 min, respectively and fitted with non-linear pseudo-second-order (PSO) kinetics model. For Cd(II) and Pb(II), the Freundlich model described the adsorption isotherm better than the Langmuir isotherm model. The maximum adsorption capacity for Cd(II) and Pb(II) was 625 and 370.37 mg g⁻¹ respectively at neutral pH. Coexisting anions of fluoride, chloride, and nitrate had a negligible influence on Cd(II) removal than the Pb(II). On the other hand, the presence of silicate and phosphate considerably affected Cd(II) and Pb(II) adsorption. The recyclability, regeneration, and reusability of the fabricated EUOL@AgNPs-SP ENMs were studied and they retained their high adsorption capacity up to five cycles. The DFT measurements revealed that SP-5 ENMs exhibited the highest adsorption selectivity for Cd(II) and the measured binding energies for Cd(II), Pb(II), are 219.35 and 206.26 kcal mol⁻¹, respectively. The developed ENM adsorbent may find application for the removal of heavy metals from water.

Recent Progress on Nanomaterial-Based Membranes for Water Treatment

Nanomaterials have emerged as the new future generation materials for high-performance water treatment membranes with potential for solving the worldwide water pollution issue. The incorporation of nanomaterials in membranes increases water permeability, mechanical strength, separation efficiency, and reduces fouling of the membrane. Thus, the nanomaterials pave a new pathway for ultra-fast and extremely selective water purification membranes. Membrane enhancements after the inclusion of many nanomaterials, including nanoparticles (NPs), two-dimensional (2-D) layer materials, nanofibers, nanosheets, and other nanocomposite structural materials, are discussed in this review. Furthermore, the applications of these membranes with nanomaterials in water treatment applications, that are vast in number, are highlighted. The goal is to demonstrate the significance of nanomaterials in the membrane industry for water treatment applications. It was found that nanomaterials and nanotechnology offer great potential for the advancement of sustainable water and wastewater treatment.

A critical review on the electrospun nanofibrous membranes for the adsorption of heavy metals in water treatment

Electrospun nanofibrous membranes (ENFMs) have many superior advantages, such as large specific surface area, high porosity, easy modification, good flexibility, and easy separation for recycling, which are consider as excellent adsorbents. In this paper, the research progress in the adsorption of heavy metals in water treatment by ENFMs is reviewed. Three types of ENFMs, including organic polymer ENFMs, organic polymer/inorganic material composite ENFMs and inorganic ENFMs are summarized, and their adsorption capacities for heavy metals in water are compared. The adsorption selectivity and capacity of ENFMs for heavy metals are depended largely on the type and number of functional groups on the surface of membranes, and usually the more the functional groups, the higher the adsorption capacity. The adsorption mechanisms of ENFMs are also mainly determined by the type of functional groups on the membrane. At present, the main challenge is to achieve the mass production of high-quality nanofibers and their actual application in the treatment of heavy metal-containing wastewater. Therefore, more consideration should be focused on the improvement of stability, mechanical strength and reusability of ENFMs. This review may provide an insight for the development of ENFMs-based adsorbents for heavy metals separation and water purification in the future.

Structural design and environmental applications of electrospun nanofibers

Nanofibers have attracted extensive attention and been applied in various fields due to their high aspect ratio, high specific surface area, flexibility, structural abundance, etc. The electrospinning method is one of the most promising and effective ways to produce nanofibers. The electrospun nanofibers-based films and membranes have already been demonstrated to possess small pore sizes, larges specific surface area, and can be grafted with different functionalities to adapt to various purposes. The environmental applications of nanofibers are one of the essential application fields, and great achievements have been made in this field. To well summarize the development of nanofibers and their environmental applications, we review the nanofiber fabrication methods, advanced fiber structures, and their applications in the field of air filtration, heavy metal removal, and self-cleaning surface. We hope this review and summary can provide readers a comprehensive understanding of the structural design and environmental applications of electrospun nanofibers.

Electrospun Bilayer PAN/Chitosan Nanofiber Membranes Incorporated with Metal Oxide Nanoparticles for Heavy Metal Ion Adsorption

Bilayer nanofiber membranes with enhanced adsorption and mechanical properties were produced by combining a layer of polyacrylonitrile (PAN) functionalized with metal oxides (MO) of ZnO or TiO2 with a layer of chitosan (CS) via consecutive electrospinning. The adsorption properties of the bilayer PAN/MO–CS nanofiber membranes against lead (Pb(II)) and cadmium (Cd(II)) ions were investigated, including the effects of the solution pH, initial ion concentrations, and interaction time. The integration of a CS layer into PAN/MO nanofibers increased the adsorption capacity of lead by 102% and cadmium by 405%, compared to PAN/MO single layer. The nonlinear optimization method showed that the pseudo-second-order kinetic model and Langmuir isotherm equation better described the adsorption results. More importantly, the incorporation of a supportive CS nanofiber layer enhanced the tensile strength of PAN/MO–CS bilayer by approximately 68% compared to the PAN/MO single layer, owing to the strong interaction between the fibers at the interface of the two layers.

A versatile, highly effective nanofibrous separation membrane

Although a wide range of fibrous filters are available for diverse filtration tasks to separate solid or oil particles from a gas or liquid medium, a single filter seldom shows versatile separation capability to perform multi-separation tasks to separate both types of particles from different media. Herein, we report a novel nanofibrous membrane that can separate oil/water emulsions (efficiency over 99.9%) at a flux as high as 4082 L m^-2 h^-1 as well as oil aerosol droplets (efficiency of 99.98% for oil droplets sized ∼330 nm) and solid aerosol particles from air (efficiency 85-99%) and micro-sized solid particles from water (efficiency >95%). The fibrous membrane is reusable to accomplish cross-medium filtration tasks. This versatile, highly efficient separation capability originates from the fine fibrous structure and an amphibious superhydrophilic-superoleophobic surface feature. This may be useful for the development of advanced technologies for various environmental protection applications.

Fabrication of PAN Electrospun Nanofibers Modified by Tannin for Effective Removal of Trace Cr(III) in Organic Complex from Wastewater

Removal of chromium ions is significant due to their toxicity and harmfulness, however it is very difficult to remove trace Cr(III) complexed with organics because of their strong stability. Herein, a novel electrospun polyacrylonitrile (PAN) nanofibers (NF) adsorbent was fabricated and modified by tannic acid (TA) by a facile blend electrospinning approach for removal of trace Cr(III) in an organic complex. Utilizing the large specific area of nanofibers in the membrane and the good affinity of tannic acid on the nanofibers for hydrolyzed collagen by hydrophobic and hydrogen bonds, the as-prepared PAN-TA NFM exhibited good adsorption toward Cr(III)-collagen complexes and effective reduction of total organic carbon in tannage wastewater. The maximal adsorption capacity of Cr(III) is 79.48 mg g-1 which was obtained at the pH of 7.0 and initial Cr(III) concentration of 50 mg g-1. Importantly, the batch adsorption could decrease the Cr(III) concentration from 10-20 mg L-1 to under 1.5 mg L-1, which showed great application potential for the disposal of trace metal ions in organic complexes from wastewater.

Electrospinning Nanoparticles-Based Materials Interfaces for Sensor Applications

Electrospinning is a facile technique to fabricate nanofibrous materials with adjustable structure, property, and functions. Electrospun materials have exhibited wide applications in the fields of materials science, biomedicine, tissue engineering, energy storage, environmental science, sensing, and others. In this review, we present recent advance in the fabrication of nanoparticles (NPs)-based materials interfaces through electrospinning technique and their applications for high-performance sensors. To achieve this aim, first the strategies for fabricating various materials interfaces through electrospinning NPs, such as metallic, oxide, alloy/metal oxide, and carbon NPs, are demonstrated and discussed, and then the sensor applications of the fabricated NPs-based materials interfaces in electrochemical, electric, fluorescent, colorimetric, surface-enhanced Raman scattering, photoelectric, and chemoresistance-based sensing and detection are presented and discussed in detail. We believe that this study will be helpful for readers to understand the fabrication of functional materials interfaces by electrospinning, and at the same time will promote the design and fabrication of electrospun nano/micro-devices for wider applications in bioanalysis and label-free sensors.

Effects of operating parameters and coexisting ions on the efficiency of heavy metal ions removal by nano-fibrous metal-organic framework membrane filtration process

The purification process of wastewater containing heavy metal ions (HMIs) using nano-fibrous metal-organic frameworks, MOF-808, embedded polyacrylonitrile membrane has been studied. The process parameters that were evaluated included feed concentration, transmembrane pressure (TMP), and membrane thickness. The effect of coexisting cations in the solution upon the removal efficiencies of Zn²⁺, Cd²⁺, Pb²⁺ and Hg²⁺ ions was also investigated. Results from the filtration experiments indicate a substantial variation in the feed volume that the membrane can treat before the permeate lead concentration reaches the allowable limit of 10 ppb, depending on the process parameter. An increase in the membrane thickness showed a significant improvement (26%) with 440 L of the treated feed volume after doubling the membrane layer. An increase in TMP could reduce the treated feed volume by 38% while a decrease in feed concentration led to a 21% increase in the treated feed volume. In the presence of other common background cations in the solution, the removal efficiency of HMIs by adsorption onto MOF-808 dropped by 18 to 37%. This result was dependent upon the HMIs, in the presence of up to three other cations but was minimal in the presence of a single cation indicative of good selectivity.