Degree Of Grafting Research Articles

Bioactive Hydrogel Formulation Based on Ferulic Acid-Grafted Nano-Chitosan and Bacterial Nanocellulose Enriched with Selenium Nanoparticles from Kombucha Fermentation.

Selenium nanoparticles (SeNPs) have specific properties that result from their biosynthesis particularities. Chitosan can prevent pathogenic biofilm development. A wide palette of bacterial nanocellulose (BNC) biological and physical-chemical properties are known. The aim of this study was to develop a hydrogel formulation (SeBNCSFa) based on ferulic acid-grafted chitosan and bacterial nanocellulose (BNC) enriched with SeNPs from Kombucha fermentation (SeNPsK), which could be used as an adjuvant for oral implant integration and other applications. The grafted chitosan and SeBNCSFa were characterized by biochemical and physical-chemical methods. The cell viability and proliferation of HGF-1 gingival fibroblasts were investigated, as well as their in vitro antioxidant activity. The inflammatory response was determined by enzyme-linked immunosorbent assay (ELISA) of the proinflammatory mediators (IL-6, TNF-α, and IL-1β) in cell culture medium. Likewise, the amount of nitric oxide released was measured by the Griess reaction. The antimicrobial activity was also investigated. The grafting degree with ferulic acid was approximately 1.780 ± 0.07% of the total chitosan monomeric units, assuming single-site grafting per monomer. Fourier-transform infrared spectroscopy evidenced a convolution of BNC and grafted chitosan spectra, and X-ray diffraction analysis highlighted an amorphous rearrangement of the diffraction patterns, suggesting multiple interactions. The hydrogel showed a high degree of cytocompatibility, and enhanced antioxidant, anti-inflammatory, and antimicrobial potentials.

Glucose-induced glycation enhances the foaming properties of Trichosanthes kirilowii seed protein isolate: Insights into structure, interfacial behavior, and proteomics

Improving the foaming properties of plant proteins has recently attracted particular interest. The foaming properties of Trichosanthes kirilowii seed protein isolate (TPI) after glucose glycation (wet heating) were investigated by structural characterization, interfacial behavior evaluation, and quantitative proteomics analysis. The results showed that the highest degree of grafting of TPI (45.54%) with glucose was observed at a reaction time of 2 h. Grafting with glucose unfolded the structure of TPI, which was confirmed by increased molecular flexibility, loss of α-helices, and exposure of hydrophobic groups. The foaming capacity and foaming stability of the TPI was greatly improved after glycation. The bubbles in the TPI–glucose conjugate foams were smaller in size, more uniform, and denser than those in the TPI foams. Moreover, the deterioration rate of the conjugate foams was significantly slower than that of the TPI foams. Mechanistically, the improved foam properties were mainly attributed to increased surface activity, accelerated air/water interfacial adsorption, and enhanced interfacial film thickness. The results of quantitative proteomics indicated that several proteins involved in foam stability and elasticity were upregulated in the initial foams of the conjugates, which partly explains the improved foam properties. Overall, G2 showed the most superior foam properties and interfacial behavior among all the samples. This study offers further insights into the mechanisms by which glycation improves the foaming properties of plant proteins and will be useful for the development of foamed foods from TPI.

Study on ferritin glycation with dextran: Physicochemical characterization and its application in the delivery of resveratrol

Ferritin exhibits promising prospects for nanoencapsulation applications, however, its susceptibility to environmental factors as a standalone carrier necessitates further consideration. In this study, the recombinant human H-chain ferritin (rHuHF) was modified with dextran (Dex) to enhance its physicochemical and functional properties. Moreover, the glycated rHuHF cavity was utilized for the encapsulation of resveratrol (Res). The results demonstrated that the glycoconjugates (Dex–rHuHF) achieved the highest grafting degree of 34.71% under the following conditions: Dex molecular weight of 40 kDa, mass ratio of rHuHF to Dex at 1:2, pH value of 7.8, relative saturation humidity of 79%, reaction temperature at 50 °C, and reaction time of 30 h. Dex interacted with rHuHF and exhibited protective effects on rHuHF under extremely acidic conditions. Each Dex–rHuHF cavity encapsulated approximately 22 Res molecules with an encapsulation rate of 10.84%. The Dex–rHuHF–Res nanoparticles displayed excellent photothermal stability and sustained release properties. Furthermore, the Dex–rHuHF–Res simulated digesta showed enhanced abilities in scavenging DPPH free radicals and inhibiting α-glucosidase activity. This work investigated the impact of Dex on the physicochemical properties of rHuHF and developed a novel approach by grafting Dex onto rHuHF for encapsulating hydrophobic substances like resveratrol, which holds potential applications in water-based food and nutraceutical formulations.

Effects of enzymatic hydrolysis combined with glycation on the emulsification characteristics and emulsion stability of peanut protein isolate

Peanut protein isolate (PPI) has high nutritional value, but its poor function limits its application in the food industry. In this study, peanut protein isolate was modified by enzymatic hydrolysis combined with glycation. The structure, emulsification and interface properties of peanut protein isolate hydrolysate (HPPI) and dextran (Dex) conjugate (HPPI-Dex) were studied. In addition, the physicochemical properties, rheological properties, and stability of the emulsion were also investigated. The results showed that the graft degree increased with the increase of Dex ratio. Fourier transform infrared spectroscopy (FTIR) confirmed that the glycation of HPPI and Dex occurred. The microstructure showed that the structure of HPPI-Dex was expanded, and the molecular flexibility was enhanced. When the ratio of HPPI to Dex was 1:3, the emulsifying activity and the interface pressure of glycated HPPI reached the highest value, and the emulsifying activity (61.08 m2/g) of HPPI-Dex was 5.28 times that of PPI. The HPPI-Dex stabilized emulsions had good physicochemical properties and rheological properties. In addition, HPPI-Dex stabilized emulsions had high stability under heat treatment, salt ion treatment and freeze–thaw cycle. According to confocal laser scanning microscopy (CLSM), the dispersion of HPPI-Dex stabilized emulsions was better after 28 days of storage. This study provides a theoretical basis for developing peanut protein emulsifier and further expanding the application of peanut protein in food industry.

Transparent, thermal stable, water resistant and high gas barrier films from cellulose nanocrystals prepared by reactive deep eutectic solvents

Nanocellulose-based film, as a novel new type of film mainly made of nanosized cellulose, has demonstrated an ideal combination of renewability and enhanced or novel properties. Considerable efforts have been made to enhance its intrinsic properties or create new functions to expand its applications, such as in food packaging, water treatment or flexible electronics. In this paper, two different types of deep eutectic solvents (guanidine sulfamate-glycerol and guanidine sulfamate-choline chloride) were formulated and applied to prepare cellulose nanocrystals with dialdehyde cellulose (DAC). The effects of reaction conditions including time, temperature and cellulose-DES ratio on the grafting degree and yield were studied. After ultrasonication, two types of CNCs, with an average diameter of 3–5 nm and an average length of 140.7–204.2 nm, were obtained. The synthesized CNCs displayed an enhanced thermal stability compared to pristine cellulose. Moreover, highly transparent (light transmittance higher than 90 %) and water stable nanocellulose based films (a wet tensile strength of higher than 30 MPa after immersing in water for 24 h) were fabricated. Besides, the obtained films exhibited low oxygen transmission rate, showing a good potential application in food packaging.

Effects of combined hot alkaline and pH-shift treatments on structure and functionality of legume protein-EGCG conjugates: Soybean-, pea-, and chickpea protein-EGCG systems

Legume proteins are appealing in the food industry for their nutrition and sustainability, but their low solubility due to the compact structure makes their applications in food industry limited. In this study, three commonly used legume proteins in food industry were selected as samples to be tested: soy protein (SP), pea protein (PP), and chickpea protein (CP). This study aims to improve the structural properties of these three proteins, so that it could promote effective grafting with epigallocatechin gallate (EGCG) through a combined hot alkaline and pH-shift treatments. Legume protein solutions were adjusted to pH 12 and heated at 80 °C for 30 min, resulting to a 13%–19% increase in free thiol content and a 59%–610% increase in surface hydrophobicity. This kind of change in structure leads to a 19%–46% increase in EGCG grafting degree. Treated protein-EGCG conjugates exhibited smaller and more uniform particle sizes, improved emulsification activity by 27%–218%, and additionally enhanced solubility, thermal stability, and antioxidant activity. Among all the tested proteins, pre-treated SP-EGCG conjugates showed the best solubility, emulsification, and thermal stability due to their highest surface hydrophobicity, highest EGCG grafting degree, and loose structure. These results indicate that combined hot alkaline and pH-shift treatment enhances the functional properties of legume proteins, expanding their potential applications as functional ingredients in the food industry.

Optimization of malic anhydrate concentration in manufacturing PP-g-MA compatibilizer on test percent of grafting degree

The difference in polarity means that two or more materials cannot react, a connecting material such as a compatibilizer is needed to react between polar and non-polar materials. This research aims to determine the effect of maleic anhydride (MA) concentration on the process of grafting MA onto polypropylene (PP) chains with the help of benzoyl peroxide (BPO) as an initiator. The method used to mix these two materials uses the blending method using an internal mixer instrument and testing the percent degree of grafting using the titration method with three repetitions of the test.The research results showed that the highest percent grafting degree occurred at a concentration of 86% PP, 11% MA, and 3% BPO, with a value of 10.28%. The Spectroscopy Fourier Transform Infrared (FTIR) analysis of Polypropylene grafted maleic anhydride (PP-g-MA) showed the presence of new peaks at wavenumbers 1707cm-1 and 1162 cm-1.Increasing the concentration of maleic anhydride had no effect on increasing the percent degree of grafting.

Preparation, characterization and functional evaluation of soy protein isolate-peach gum conjugates prepared by wet heating Maillard reaction

This study was conducted to formulate a conjugate of soy protein isolate (SPI) and peach gum (PG) with improved functional properties, interacting at mass ratios of 1:1, 1:2, 1:3, 2:1, and 2:3 by Maillard reaction via wet heating method. Conjugation efficiency was confirmed by grafting degree (DG) and browning index (BI). Results indicated that DG increased with increasing concentration of PG, and decreased with increasing pH, whereas no remarkable change was observed with increasing reaction time. The conjugates were optimized at a ratio of 1:3. SDS-PAGE confirmed conjugate formation, Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) verified conjugate secondary structural changes, and scanning electron microscopy (SEM) indicated significant overall structural changes. The functional properties, solubility, emulsifying stability, water holding, foaming, and antioxidant activity were significantly improved. This study revealed the wet heating method as an effective approach to improve the functional properties of soy protein.

Surface Modification of Polyethylene Terephthalate Track-Etched Membranes by 2,2,3,3,4,4,5,5,6,6,7,7-Dodecafluoroheptyl Acrylate for Application in Water Desalination by Direct Contact Membrane Distillation.

In this work, the surfaces of poly (ethylene terephthalate) track-etched membranes (PET TeMs) with pore sizes of 670-1310 nm were hydrophobized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA) by photoinitiated graft polymerization. Attenuated total reflection FTIR spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDX), and contact angle measurements were used to identify and characterize the TeMs. The optimal parameters for graft polymerization were determined as follows: polymerization time of 60 min, monomer concentration of 30%, and distance from the UV source of 7 cm. The water contact angle of the modified membranes reached 97°, which is 51° for pristine membranes. The modified membranes were tested for water desalination using direct contact membrane distillation (DCMD) method. The effects of membrane pore size, the degree of grafting, and salt concentration on the performance of membrane distillation process were investigated. According to the results obtained, it has been concluded that large pore size hydrophobic TeMs modified by using DFHA could be used for desalinating water.

Improved stability of sesame paste by peanut protein-flaxseed gum conjugation

The oil-water separation phenomenon in sesame paste poses a challenge for the storage of sauce products. In this study, soy protein isolate (SPI), peanut protein isolate (PPI) and flaxseed gum (FG) conjugates were prepared to stabilize the solid-liquid phases of sesame paste. The results indicated that the highest degree of grafting (25.07%) was observed in a ratio of PPI:FG = 4:1 (PF2). The interaction between proteins and FG generated the extension of the protein molecule and increased structural disorder. PPI-FG conjugates exhibited the lower surface hydrophobicity and higher thermal stability. The addition of 4% PF2 to sesame paste led to a reduction of 5.06% oil separation rate and showed higher storage modulus (G′), loss modulus (G″), apparent viscosity, and hardness. A stable and continuous three-dimensional network was created to physically entrap the oil, resulting in a more uniform distribution of oil droplets and a reduced particle interaction of sesame paste.

Stability and lipid oxidation of oil-in-water emulsion stabilized by Maillard conjugates of soybean phosphatidylethanolamine with different polysaccharides

Lipid oxidation and instability in oil-in-water (O/W) emulsion are the main challenges in emulsion-based foods. Polysaccharide-induced Maillard conjugation of soybean phosphatidylethanolamine (SP) holds great potential in improving physicochemical stability of emulsions. This work applied tamarind gum, pectin, inulin and maltodextrin to conjugate with SP to obtain the four Maillard conjugates (MCs), and investigated their difference in interface and anti-oxidant abilities in emulsions. Results showed that lower polymerization degree of polysaccharide moieties (tamarind gum＞pectin＞maltodextrin＞inulin) caused higher glycation degree in MC: inulin-SP-MC＞maltodextrin-SP-MC＞pectin-SP-MC ≈ tamarind gum-SP-MC, which corresponded their color changes. Compared with unconjugated mixtures, interface activity and anti-oxidant abilities of MCs were strengthened. Among the four MCs, tamarind gum-SP-MC (7.77 mN/m) and pectin-SP-MC (8.42 mN/m) could decrease interfacial tension more largely. It was due to the faster interface saturation benefited from broader steric network of tamarind gum and pectin moieties, and stable interfacial absorption facilitated by improved zeta potential and lipophilicity. Pectin-SP-MC also exhibited the highest anti-oxidant ability (DPPH scavenging ability of 97.81% and ferric-reducing antioxidant power of 2.742 A). It was attributed to the combined effects of grafting degree, interface activity and chain length of pectin moiety. As a result, emulsions stabilized by pectin-SP-MC had less water loss, smaller droplet sizes, and lower contents of oxidation products. Maillard reaction between SP and pectin was favorable to produce MCs with higher potential for the improvements of physical and oxidative stability of O/W emulsions.

Designing Advanced Cross-Linked Proton Exchange Membranes with Enhanced Structural Homogeneity and Proton Conductivity via Radiation-Induced RAFT Polymerization.

This study introduces an innovative approach to fabricate well-defined cross-linked proton exchange membranes (PEMs) using radiation-induced reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization on cost-effective ethylene tetrafluoroethylene (ETFE) films. The incorporation of the RAFT mechanism into the cross-linking process significantly enhanced structural homogeneity, providing uninterrupted proton conductivity. Thorough characterizations confirmed the successful grafting of polystyrene (PS) chains onto ETFE films and subsequent sulfonation. Despite a reduction in proton conductivity attributed to restricted chain movements, a notable improvement in chemical stability was observed after cross-linking reactions. Chemical stability of the cross-linked membranes increased approximately 4-fold compared to those synthesized without a cross-linker. The synthesized PEMs with degrees of grafting at 45% and 67% demonstrated superior proton conductivity, outperforming various alternatives, including commercial Nafion samples. Specifically, these cross-linked membranes exhibited promising proton conductivity values of 93.7 and 139.1 mS cm-1, respectively. This work highlights the potential of radiation-induced RAFT-mediated polymerization in carrying out cross-linking reactions as an efficient pathway for designing well-defined high-performance PEMs, offering enhanced homogeneity and conductivity compared to existing literature counterparts.

Enhancing Sensitivity in SARS-CoV-2 Rapid Antigen Testing through Integration of a Water-Soluble Polymer Wall.

Lateral flow immunoassays (LFIAs) are recognized for their practicality in homecare and point-of-care testing, owing to their simplicity, cost-efficiency, and rapid visual readouts. Despite these advantages, LFIAs typically fall short in sensitivity, particularly in detecting viruses such as SARS-CoV-2, thus limiting their broader application. In response to this challenge, we have innovated an approach to substantially enhance LFIA sensitivity. This involves the integration of a water-soluble dextran-methacrylate polymer wall with a 15% grafting degree positioned between the test and control lines on the LFIA strip. This novel modification significantly improved the sensitivity of the assay, achieving detection limits as low as 50 pg mL-1 and enhancing the sensitivity by 5-20-fold relative to existing LFIA kits available on the market. Furthermore, our developed LFIA kit (WSPW-LFIA) demonstrated exceptional specificity for SARS-CoV-2. Coupled with a straightforward fabrication process and robust stability, the WSPW-LFIA represents a promising advancement for real-time in vitro diagnosis across a spectrum of diseases.

Nano silica grafted on modified polyacrylonitrile fiber improves the interfacial strength of fiber‐reinforced concrete

AbstractCement is known to be brittle and usually reinforced with fibers. However, there is a lack of effective chemical bonding between organic fibers and inorganic cement, resulting in a weaker interfacial bonding strength. In this paper, amino hyperbranched polymer (HBP) was used to modify the surface of polyacrylonitrile (PAN) fibers, and then silica nanoparticles (SiO2 NPs) were grafted on the surface of modified PAN fibers to realize the inorganic treatment of organic fibers. The modified PAN fibers applied to cement concrete can significantly enhance the interfacial strength between the fibers and cement. The morphology and chemical composition of the modified PAN fibers were characterized by scanning electron microscope, atomic force microscope, electron energy dispersive spectroscopy, and Fourier transform infrared spectroscopy, and the influence of grafting conditions on grafting effect was analyzed. The results show that SiO2 NPs were evenly distributed on the surface of PAN fiber. When SiO2 NPs concentration was 4%, grafting temperature was 50°C, and grafting time was 4 h, the grafting degree of SiO2 NPs grafted PAN fiber can reach to 1.4%. After coating with SiO2 NPs, the pullout bonding strength of the PAN fiber was increased from 5.5 to 6.5 cN.

Radiation grafted polyacrylic acid–polyurethane foam copolymer for efficient toxic metal removal from aqueous waste: a sustainable approach to waste management

The acrylic acid-grafted functionalized base polyurethane foam (PAA-g-PUf) is synthesized through mutual radiation grafting technique using acrylic acid as functional monomers and polyurethane form (PUf) with macroporous structure as base polymer, for the extraction of lead from the aqoueous waste streams. The incorporation of functionality on PUf is identified and confirmed by FT-IR spectroscopy, degree of grafting and thermal stability by TGA–DSC technique while the surface morphology, and pores dimensions are evaluated by SEM techniques. The kinetics measurements indicate that the synthesized sorbent reaches its saturation sorption capacity within 10 min at ~ 25 °C under near-neutral pH condition. The monolayer sorption capacity of the synthesized PAA-g-PUf for lead ion (Pb2+) is calculated from Langmuir’s model and found to be ~ 257 mg g−1, which is quite good as compared to the other functionalized material available. These grafted foams are quite efficient over a wide range of concentrations and temperature of the experimental solutions. In this study, the adsorbed lead ions are eluted out in 0.5 M HCl strippent efficiently. These sorbents exhibit excellent reusability up to five cycles without losing appreciable capacity, suggesting better usability in real water samples for many cycles. The polyurethane foam used was obtained from municipal waste, and hence, they cannot generate any additional secondary waste to the environment and make the process more sustainable and economically viable.Graphical abstract

Fabrication of an antibacterial system of arginine-modified chitosan with AgNPs-loaded montmorillonite for food preservation

Ag-based materials have potent antibacterial effects, but their potential toxicity problems should not be underestimated, so it is urgent to construct a safe and non-resistant dual antibacterial system. In this study, we utilized tea polyphenols (TPs) and montmorillonite (MMT) to control the growth of silver nanoparticles (AgNPs). Then, we combined the AgNPs with arginine to construct a synergistic antibacterial system of arginine-modified chitosan-assisted AgNPs-loaded MMT (ACS/G/AgNPs@MMT). The results showed that AgNPs with a uniform dispersion of 6.72 ± 4.66 nm and ACS with a grafting degree of 0.153 were successfully prepared, and the synergistic antibacterial effect between ACS and AgNPs@MMT was verified by the FIC index, and the antibacterial rate could still reach 99.9 % when the additions of ACS and AgNPs@MMT were reduced by 75 % and 79.1 %, respectively. The ACS/G/AgNPs@MMT-2 composite film exhibited excellent mechanical properties, water vapor/UV barrier properties, antioxidant activity, degradation properties, and biosafety. In addition, the synergistic effect enabled the ACS/G/AgNPs@MMT-2 film to achieve antibacterial rates of 99.24 ± 0.19 % against E. coli and 99.49 ± 0.40 % against S. aureus, and the film exhibited excellent long-lasting antibacterial performance due to the slow release of Ag+ (only about 11.27 % of Ag+ was released in 20 days). Finally, the ACS/G/AgNPs@MMT-2 film could significantly improve the food preservation ability. In conclusion, this study indicates that the film could be used as a novel antibacterial packaging material.

Synthesis and Characterization of Self-Assembled Highly Stearate-Grafted Hydroxyethyl Starch Conjugates

Polysaccharide-based nanoformulations with tailored hydrophobic properties have become a frontier in nanomedicine applications. Herein, highly hydrophobicized hydroxyethyl starch (HES) conjugates were synthesized by grafting stearic acid (SA) with HES via a carbodiimide-mediated reaction. A detailed NMR characterization of HES and the conjugates was studied to obtain structural information. The grafting ratio of the stearate-HES (St-HES) conjugates was determined from 1H NMR spectra as 29.4% (St-HES29.4) and 60.3% (St-HES60.3). Thermal analyses and X-ray diffractograms suggested an entire transition from amorphous HES to a semicrystalline (St-HES60.3) character upon increasing the degree of grafting. Both conjugates, St-HES29.4 and St-HES60.3, were able to form self-assembled particles with a diameter of 130.7 nm and 152.5 nm, respectively. SEM images showed that the self-aggregates were mostly spherical in shape. These conjugates can be employed to entrap highly hydrophobic drugs with an increased encapsulation efficiency and loading capacity.

The effect of mixing sequence on synthesis of PP-g-GMA compatibilizer for multilayer packaging (MLP) compounding

Melt recycling Multilayer Packaging (MLP) waste is difficult due to challenging separation procedures. However, blending techniques with compatibilizers can simplify MLP waste melt recycling. PP-g-GMA is a common compatibilizer in polyolefin and PET blends. PP-g-GMA compatibilizer was synthesized by utilizing an internal mixer at 175℃, 50 rpm, and 10 min using styrene as a comonomer. Titration was a method to examine effect of three different sequences of adding the BPO initiator on GMA grafting. Each sequence's PP-g-GMA samples were compounded with MLP waste using a twin-screw extruder and injection molded to make tensile test specimens. FTIR analysis shows that the GMA and Styrene monomers had grafted onto the PP polymer backbone, with the GMA grafting degree by varying mixing sequence. Sequence 3, which introduced initiator, GMA, and styrene simultaneously to PP melt, yielded PP-g-GMA with the most significant GMA grafting degree of 5.11%. Adding PP-g-GMA produced from sequence 3 into the MLP melt enhanced the highest increase in tensile strength and elongation at break of the MLP/PP-g-GMA compound.

Synthesis and Characterization of Emulsifiers Based on the Maillard Reaction and Its Application in Stabilized DHA Algal Oil Nanoemulsions.

The aim of this study was to optimize the formation of sodium caseinate (CS) and gum arabic (GA) complexes through the Maillard reaction and to evaluate their effectiveness in improving the emulsification properties and stability of docosahexaenoic acid (DHA) nanoemulsions. First, the best target polysaccharides were selected, and the best modification conditions were determined using orthogonal experiments. Secondly, the response surface experiments were used to optimize the preparation process of the emulsion. The stability, in vitro digestion characteristics, and rheological characteristics of the emulsion prepared by means of CS-GA were compared with the emulsion prepared using a whey protein isolate (WPI). After the orthogonal test, the optimal modification conditions were determined to be a reaction time of 96 h, a CS-GA mass ratio of 1:2, a reaction temperature of 60 °C, and a degree of grafting of 44.91%. Changes in the infrared (IR), Raman, ultraviolet (UV), and endogenous fluorescence spectra also indicated that the complex structure was modified. The response surface test identified the optimal preparation process as follows: an emulsifier concentration of 5 g/L, an oil-phase concentration of 5 g/L, and a homogenization frequency of five, and the emulsion showed good stability. Therefore, the use of a nanoemulsion as a nanoscale DHA algal oil delivery system is very promising for extending the shelf life and improving the stability of food.

Electrospun nanofiber membrane of 14-crown-4 polyimide by in situ grafting diamino crown ether for highly selective Li+ adsorption and separation

The global demand for lithium is increasing rapidly with the blossom of the new energy field. It is imperative to develop a sustainable and efficient approach for recovering Li+ resources from salt-lake brine. In this study, diamino dibenzo-14-crown-4 ether (DAB) was chemically grafted on 14-crown-4 polyimide (14C4PI) by nucleophilic substitution to fabricate nanofiber membrane by electrospinning method. The crown ether loading of DAB-g-14C4PI membrane was increased from 1.38 up to 2.27 mmol/g, and the grafting degree reached 83.4 % by regulating the additive amount of DAB and the reaction time. The Li+ equilibrium adsorption capacity of the DAB-g-14C4PI nanofiber membrane was enlarged from 40.17 (14C4PI) to 60.71 mg/g. The adsorption for Li+ on the membrane was a monolayer chemical adsorption process proved by the adsorption kinetic and isotherm models. The separation factors of the membrane for Li+/Na+, Li+/K+, Li+/Mg2+ and Li+/Ca2+ were 69.24, 79.4, 37.46 and 67.53, respectively. DFT calculations indicated the raised Li+ adsorption capacity was also ascribed to the enhanced adsorption energy from −107.71 to −122.84 kcal/mol, owing to the relatively higher electric charge density (−0.478 vs −0.448 a.u.). In summary, this work put forward a novel method to fabricate a nanofiber membrane with a high crown ether loading for the extraction of lithium resources.