•The nanocellulose-based aerogels were formed via electrostatic attraction without chemical crosslinking.•The nanocellulose-based aerogels have wet strength and shape memory.•The aerogel adsorbent ...shows high adsorption capacity and adsorption rate.•The aerogel adsorbent exhibits good reusability.
This study describes the preparation of an aerogel adsorbent based on nanofibrillated cellulose(NFC) and polyethyleneimine(PEI) via electrostatic combination without chemical crosslinking. Purely physical crosslinking between NFC and PEI was confirmed by attenuated total refraction-Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). The NFC/PEI hybrid aerogels exhibited good structural stability and shape recovery in water. Absorption experiment shows that the hybrid aerogels are excellent adsorbents for the removal of heavy metal ions owing to the highly porous structure and the existence of plenty of amine groups. Thermodynamic and kinetic study showed pseudo-second-order equation and Langmuir model (R2 > 0.999) as the best fit. The maximum adsorption capacity of Cu(II) and Pb(II) according to Langmuir model was 175.44 mg/g and 357.44 mg/g, respectively. Besides, the Cu(II) or Pb(II) loaded NFC/PEI aerogel could be easily regenerated by EDTA and retain the adsorption capacity after repeatedly using. This environmentally friendly hybrid aerogels with high-performance are promising candidates for sewage disposal and metal pollution treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Cement is one of the mostly used construction materials due to its high durability and low cost, but it suffers from brittle fracture and facile crack initiation. This article describes the use of ...naturally-derived renewable cellulose nanofibers (CNFs) to reinforce cement. The effects of CNFs on the mechanical properties, degree of hydration (DOH), and microstructure of cement pastes have been studied. It is found that an addition of 0.15% by weight of CNFs leads to a 15% and 20% increase in the flexural and compressive strengths of cement paste. The enhancement in mechanical strength is attributed to high DOH and dense microstructure of cement pastes after adding CNFs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Herein, lignocellulosic nanofibrils (LCNF) suspension containing 0.1, 3.9, and 17.2 wt% lignin were utilized to fabricate films by filtration and pressing process. The stiff nature of fibrils ...containing lignin made them less able to conform during filtration, resulting in more uneven surface structure with higher roughness value. Lignin in the films interfered in hydrogen bonding between cellulose nanofibrils, thus impairing mechanical property of the film, such as tensile stress and Young’s modulus. Due to the presence of chromophore groups, lignin absorbed light and the light transmittance of film was decreased. However, the film containing lignin displayed unusually high hydrophobicity with water contact angle of 88° and maximal weight loss temperature (
T
max
) of 372 °C. Overall, this study provides useful knowledge for understanding the result of lignin on the formation, surface morphology and physical behavior of LCNF films, especially in related bioproducts that requires low hydrophilicity, high roughness and high thermal stability.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•LNP can be mixed with CNF, PVA and borax to assemble self-healable hydrogel.•CNF acted as reinforcing agents to enhance the interaction between polymer matrix.•LNP acted as ...nano-spacers to impede aggregation between hydrophilic materials.•Tuning LNP content can be an effective way to tailor the hydrogel property.
To face the increasing demand of self-healing hydrogels with high performance for various applications ranging from bioscaffolds, culture matrices to responsive electronic devices, lignin nanoparticle-containing composite hydrogels are assembled via dynamic reversible didiol-borax linkages and linear polyvinyl alcohol (PVA) and cellulose nanofibrils (CNF). Lignin nanoparticles (LNP) acted as nano-spacers to fill the three-dimensional network, leading to enhanced viscoelasticity and thermal stability of hydrogel. With the increased LNP content, composite hydrogel exhibited the highest storage modulus and loss modulus of 8504 Pa and 3260 Pa, respectively, 28 times and 18 times greater than pure hydrogel without LNP. The resulting hydrogel showed porous network structure and excellent recovery behavior under continuous step strain. In general, this work demonstrates a facile approach to transfer nanoscale building blocks to 3D polymeric materials with tunable dynamic rheology properties and may provide a new prospect for the rational design of functional hydrogels for applications that require high rheological property.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Two lignin-containing cellulose nanofibril (LCNF) samples, produced from two unbleached kraft pulps with very different lignin contents, were used to produce reinforced polyvinyl alcohol (PVA) ...hydrogels. The effects of LCNF loading (0.25–2 wt %) and lignin content on the rheological and mechanical properties of the reinforced hydrogels were investigated. The 2 wt % LCNF-reinforced PVA hydrogels exhibited up to a 17-fold increase in storage modulus and a 4-fold increase in specific Young’s modulus over that of pure PVA hydrogel. Both the mechanical and rheological properties of LCNF-reinforced PVA hydrogels can be tuned by varying LCNF loading and LCNF lignin content. During LCNF production, lignin reduced cellulose depolymerization, resulting in LCNF with high aspect ratios that promoted entanglement and physical bridging of the hydrogel network. Free lignin particles generated during LCNF production acted as multifunctional nanospacers that increased porosity of the hydrogels. Because LCNFs were produced from unbleached chemical pulps, which have high yields and do not require bleaching, this study provides a more sustainable approach to utilize lignocelluloses to produce biomass-based hydrogels than by methods using commercial bleached pulps.
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IJS, KILJ, NUK, PNG, UL, UM
All-cellulose paper-based composites with underwater superoleophobicity and high-wet-strength were developed by casting a barrier layer of bacterial cellulose (BC) on a filter paper substrate. To ...optimize the pore structure of barrier layer, slow gel process of BC dispersion was conducted via acidification and solvent exchange. 1,2,3,4-butanetetracarboxylic acid was used to improve the wet strength and surface hydrophilicity through the crosslinking reaction between fibers. The underwater oil contact angles are higher than 150° in neutral environment, and slightly decrease under acid and alkali conditions. Combined with the micron-sized pore structure of BC barrier layer, the composite papers show good separation performance of oil-in-water emulsion. A denser BC layer can significantly improve the separation efficiency, but also lead to the reduction of flux. During the gelation of BC barrier layer, the increase in the ethanol/water ratio of the dispersion medium is able to increase the flux without obvious negative impact on the separation efficiency. When the ethanol/water ratio is 80%, the separation efficiency and water flux reach 99.2% and 1320 L m
−2
h
−1
·bar
−1
for the emulsified soybean oil with the average size of 13 μm, respectively. This type of all-cellulose composite papers provides a new idea for the fabrication of membrane materials for oil–water separation.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Herein, we fabricated a starch-based flexible coating for food packaging papers with excellent hydrophobicity and antimicrobial properties. FTIR (Fourier transform infrared) and XRD (X-ray ...diffraction) spectra revealed the homogeneous dispersion of the ZnO nanoparticles (NPs) in the composite film within 5% ZnO NP dosage. SEM (scanning electron microscope) and AFM (atomic force microscope) micrographs confirmed the increased roughness on the composite film with the increased dosages of ZnO NPs. Hydrophobic characteristics showed that dramatic enhancement was obtained in the values and stabilities of DCAs (dynamic contact angles) in the resultant film and coated paper. TG (thermogravimetry) results demonstrated the increased thermal stabilities of the composite films. Significantly, a decreased water vapor transmission rate was observed in the coated paper. When 20% guanidine-based starch and 2% CMC (carboxy methyl cellulose) was added, a flexible coating with excellent antimicrobial activity towards
can be obtained. Furthermore, the migration of ZnO NPs into the food simulants was well below the overall migration legislative limit. The resultant starch-based flexible composite film and coated paper established an effective approach to develop a green-based material for food packaging applications.
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•Lignosulfonate (LS) was an excellent dispersant for hexagonal boron nitride (h-BN) since its phenolic hydroxyl groups and three-dimensional structure.•Three-dimensional thermally ...conductive pathways were well built and optimized when the h-BN/cellulose nanofiber (CNF) ratio was 3:1 (w/w).•The through-plane thermal conductivity of LS-BN/CNF/polyvinyl alcohol (PVA) composite was high up to 1.22 W/mK.•This LS-BN/CNF/PVA composite held great practical potentials in thermal interface materials as a key building block.
Hexagonal boron nitride (h-BN) is an excellent thermally conductive and electrically insulative material. However, the formation of heat transfer pathways of h-BN in thermal interface materials is restricted due to its poor aqueous dispersity. Herein, water-soluble lignosulfonate (LS) is used to promote the dispersion of h-BN, the phenolic hydroxyl and three-dimensional structure of LS could form hydrogen bonding or steric hindrance with h-BN under ultrasound treatment. After mixing with cellulose nanofiber (CNF), the three-dimensional thermally conductive pathways are built in LS-BN/CNF aerogel through freeze-drying. The results show that the through-plane thermal conductivity of LS-BN/CNF/PVA composite with 0.2 wt% LS (LS0.2-BN/CNF/PVA) exceeds 1.22 W/mK when the h-BN/CNF ratio is 3:1 (w/w), which is 6.1-fold of that of PVA film (0.20 W/mK). The initial decomposition temperature and tensile strength of LS0.2-BN/CNF/PVA composite are 205 °C and 38.5 MPa, respectively, demonstrating acceptable thermal stability and mechanical properties for electronics as thermal interface and packing material. Overall, this work put forwards an effective approach to disperse h-BN and paves the way in developing high-performance thermal interface materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Graphene/silver nanoparticles coating exhibited timely transfer of electrons and heat due to the 3D electric conductive network.•The aluminum film played the dual functions of ...electromagnetic interference shielding and heat transfer.•The material showed excellent electrical conductivity and electromagnetic interference shielding effectiveness of 4431 S/m and 92.29 dB, respectively.•The material exhibited outstanding mechanical properties with tensile strength of 32 MPa and elongation at break of 6.65%.
Rubber and plastic are widely acted as substrates in flexible electromagnetic shielding (EMS) materials. However, these materials have several drawbacks in practical applications, such as potential environmental concerns and difficulties in degrading. In this work, a biodegradability paper-based material composed of electromagnetic wave loss layer (graphene/ silver nanoparticles (AgNPs) coating) and reflective layer (aluminum film layer) was successfully fabricated. The electromagnetic wave loss layer constructed three-dimensional (3D) electric conductive network to facilitate the timely transfer of electrons and heat energy obtained from electromagnetic waves. Meanwhile, the reflective layer received electrons and heat from the electric conductive network and make a small quantity of transmission wave back to the wave loss layer. The resulting material exhibited an ultrahigh electromagnetic interference shielding effectiveness (EMI SE) of 92.29 dB within 8–13 GHz, electrical conductivity of 4431 S/m, mechanical properties with a tensile strength of 32 MPa and elongation at break of 6.65%. Compared to the traditional EMS materials, the composite material integrated with excellent EMI SE, heat transfer performance, and weatherability, which has potential applications in microelectronics, high integrated circuits, and flexible electronic fields.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lignin, as the sole renewable aromatic resource in nature, has great potential for replacing fossil resources. However, the complexity of its structure limits its high value utilization, and the ...molecular weight distribution and dissolution behavior of lignin in alkaline solutions is still unclear. In this study, a conventional lignin separation during the pulping process in an alkaline hydrothermal system was performed by controlling the amount of NaOH, reaction temperature and holding time. Various analysis methods, including GPC, 2D–HSQC NMR and FTIR were used to study the characteristics of lignin fragments dissolved from wood. We were aiming to understand the rule of lignin dissolution and the recondensation mechanism during the process. The results showed dissolution of lignin due to ether bond fracturing by OH− attacking the Cα or Cβ positions of the side chain with penetration of NaOH, and the lignin fragments in solution recondensed into complex lignin with more stable C–C bonds. The experimental results also prove that the average molecular weight increased from 4337 g/mol to 11,036 g/mol and that holding time from 60 min to 120 min at 150 °C with 14 wt% of NaOH.
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