Multifunctional materials for water purification have attracted significant attention due to the increased water pollution problems. However, fabricating the low-cost, effective, and recyclable separation material for wastewater containing various hazardous substances is still a challenge. Herein, we developed an Ag/TiO2@PDMS coated cotton fabric with self-cleaning ability, high flux, superior visible-light photocatalytic ability, and recyclability via the “powder?+?glue” strategy. The composites are superhydrophobic (water contact angle 157°) and show high separation efficiency. After 20 times of repeated use, the separation efficiency remains 16,322 Lm?2 h?1, and methylene blue (MB) 's degradation rate remains almost unchanged. The high oil purification, catalytic property, excellent stability in harsh conditions, and recyclability enable the material as a satisfactory candidate for water purification.
Graphical abstractIonic cellulose nanocrystals (CNCs) are interesting surface-active particles for encapsulating a lipophilic liquid in water. A CNC is modified chemically to a negative charge (an S-CNC) by surface treatment with sulfuric acid. Despite the amphiphilic nature of S-CNCs, it is difficult to determine the degree of substitution for emulsification of lipophilic liquids, especially when the surface energy is low and polarity is high. Here, we control the substitution of S-CNCs by desulfation of S-CNCs (dS-CNCs) using a low-concentration hydrochloric acid solution. Decreased surface charge of S-CNCs was expected, and the lipophilic affinity of dS-CNCs increased compared with those of S-CNCs. Six oils with differing surface tensions were selected for determination of the effect of charged CNCs on emulsification. The stability of the emulsion was evaluated by emulsion fraction, emulsion particle size, and surface tension of emulsified solutions from dS-CNCs and oils.
Graphical abstractMembrane applications for the separation of surfactant-stabilized emulsions are often constrained by a deficiency in permeability and anti-fouling properties. Herein, special wetted cotton fabric with a protective layer (P-MH@CF) for durable anti-fouling performance was synthesized by a two-step method, which was related to interfacial ion migration technology and unilateral spraying treatment. Permeability of water and separation performance of P-MH@CF membrane were investigated systematically. Emulsions stabilized by anionic, cationic, or non-ionic surfactant were successfully separated with high efficiency. In the process of separation, the oil droplets surrounded by surfactants were difficult to demulsify and gathered physically on the membrane surface to form a “cream layer”. The stearic acid acted as a protective layer, like a quilt, protecting the membrane from contamination. The membrane retained robust reusability for separation even after the “cream layer” had been washed off, which was promising for the remediation of oily wastewater containing surfactants.
Graphical abstractThis study introduces an effective route to fabricate chitosan (CS)-based film. The films were prepared through cross-linking reaction between CS and hydroxyethyl cellulose (HEC) using epichlorohydrin (ECH) as the cross-linker and simultaneously in-situ loading with CuO nanoparticles. FT-IR and loading efficiency results indicated the occurrence of inter- and intra-molecular cross-linking reaction between CS and HEC. XRD and EDS analyses showed that the CuO nanoparticles were evenly deposited onto CS film matrixes. SEM characterization showed that the films were of compact, dense and uniform cross morphologies, as well as obvious voids. The films also exhibited desired swelling ratio and water vapor permeability. The enhanced tensile strength was obtained with a maximum value of 77.02?±?3.26 MPa, while the stretch-ability slightly decreased. The thermal stability of the films decreased after cross-linking with HEC. The antibacterial ability of the films was generally improved with the increase of HEC and ECH contents.
Graphical abstractPreparation and properties of epichlorohydrin-cross-linked chitosan/hydroxyethyl cellulose based CuO nanocomposite films
Exploitation of cotton fabric as electromagnetic interference (EMI) shielding substrates have attracted a growing interest due to their desirable low carbon footprint, economic feasibility, and sustainability. Herein, a facile strategy was proposed for preparing a cellulose-based multifunctional PNIPAAm/PPy hydrogel/cotton (PPHC) EMI shielding composites with simultaneous high-efficient electro-photo-thermal conversion and comfort regulation functions. The PPHC was fabricated via in situ polymerization conductive PPy hydrogel on cotton substrate followed by deposition of PNIPAAm. Benefiting from the unique interconnected three-dimensional networked conductive structure of PPy hydrogel, the obtained PPHC composites exhibited high conductivity (15 mS/cm), and EMI shielding effectiveness (EMI SE?~?40 dB) in the frequency of 8.2–12.3 GHz. Moreover, the PNIPAAm coating endowed the composite fabrics with adjustable wettability performance in response to external temperature, leading to excellent comfort regulation performance. This work provided feasible avenue toward low cost and sustainability cotton-based EMI shielding composites with efficient EMI shielding and comfort regulation performance.
Graphical abstractVulcanized fibers are all-cellulose materials made from cotton and/or wood cellulose after aqueous zinc chloride treatment. These materials were invented in the UK in the mid-nineteenth century and is widely used because of their excellent characteristics, such as impact resistance and electrical insulation. Recently the matured vulcanized fibers have been recognized as renewable and biodegradable materials and reevaluated with advanced cellulose technologies derived from cellulose nanofibers (CNFs) and all-cellulose composites. The microscopic analysis based on the improved freeze-drying method revealed that the strength of vulcanized fiber sheets can be attributed to the chemically defibrillated CNFs. The architecture is similar to all-cellulose composites made from the same raw materials in which the residual cellulose fibers serve as reinforcement, and the CNFs serve as adhesives or matrix components. In this report, we describe the history and structural characteristics of vulcanized fibers and introduce a new aspect in aqueous zinc chloride treatment of cellulose.
Graphical abstractThis study prepared a waterproof cellulose nanofibril (CNF) sheet via the deposition of an alkyl ketene dimer (AKD) on the sheet’s controlled porous structure. The porosity of the CNF sheet was controlled by drying under different conditions, which included hot-press drying (HD) and solvent-exchange drying (SD), and the effect on the hydrophobization and water-related barrier performance of the sheet were investigated. When the SD sheet was immersed in an AKD wax solution, the sheet exhibited super-hydrophobicity and a lower water vapor transmission rate, compared with the HD sheet. This indicated that the porous structure of the SD sheet enabled AKD to be adsorbed on both the surface and the inner surface and it filled in the pores of the sheet, thereby giving rise to excellent waterproofing properties. The performance of a hydrophobized SD sheet as a water barrier material was comparable to a linear low-density polyethylene film. This study confirms the possibility for AKD wax to be immersed in a porous CNF sheet and used as a potential barrier material in hydrogel packaging.
Graphical abstractA cellulosic material has been synthesized that could efficiently and selectively adsorb organic and inorganic contaminants from aqueous solutions without interference from competing adsorption sites. Cellulose-graft-tetraethylenepentamine molecular imprinted polymer (C-TEPA-MIP) was synthesized by using 4-nitrophenol (4-NP) as the template. The C-TEPA-MIP adsorbent could adsorb 4-NP and Cr(VI) simultaneously and selectively, without being affected by the competitive adsorption sites of each of these pollutants. The adsorption of 4-NP was predominantly due to the imprinted sites of 4-NP in C-TEPA-MIP that were located inside of the adsorbent, whereas that of Cr(VI) was primarily due to the amine groups of TEPA found on the surface of the adsorbent. Compared with the non-imprint polymer synthesized without the template, C-TEPA-MIP showed higher selectivity for both 4-NP and Cr(VI) in unitary and binary systems. In addition, C-TEPA-MIP exhibited good stability and recyclability for 4-NP, which makes it a promising candidate material for applications concerning wastewater treatment.
Graphical abstractThe development of a simple surface barrier discharge plasma device is presented to enable more widespread access to and utilization of plasma technology. The application of the plasma device was demonstrated for pretreatment of wood prior to application of protective coatings for outdoor usage. The coatings' overall performance was increased, showing a reduction or absence of cracking due to weathering on plasma-pretreated specimens. Moreover, after ten months of outdoor weathering, the plasma-pretreated specimens showed fewer infections with biotic factors and improved adhesion performance in cross-cut tests, while the surface gloss performed independently from plasma pretreatment. In contrast to that, plasma-pretreated specimens were slightly more prone to discoloration due to outdoor weathering, whereas the plasma pretreatment did not impact the initial color after coating application.
Graphic abstractThe development of a versatile platform that can separate oil/water mixture, remove dye from water, and purify wastewater is extremely desirable, yet still hard to realize. Herein, to address this challenge, a composite hydrogel was produced by freezing–thawing treatment using chitosan, polyvinyl alcohol, and carbon black as the raw materials. The obtained hydrogel displayed both slippery oil-repellency and water-affinity in air, underwater, when submerged in oil, and exploiting this special wettability, the hydrogel coated mesh can be used to separate oil/water mixtures efficiently. After 25 oil–water separation cycles, the hydrogel-coated filter still had a separation efficiency of over 98%. With its superhydrophilicity and active functional groups, the resulting hydrogel was able to absorb dye molecules dissolved in water effectively. Due to the photothermal effect of carbon black, the local temperature of the hydrogel was increasing quickly under sunlight illustration, which allowed it to be an advanced platform for daily wastewater purification through solar distillation.
Graphical abstractA versatile hydrogel platform for oil–water separation, dye adsorption, and domestic wastewater purification was developed.
Cellulose-based matrices are expected to be ideal enzyme carriers due to their sustainability and biocompatibility. However, the linkages between immobilized enzymes and celluloses often suffer from low-density and non-biodegradability, leading to inefficient loading of enzymes as well as persistent generation of solid wastes after reuse. In the present study, cellulose-based functional materials with degradable polycarbonates brushes have been successfully synthesized as enzyme carriers via ring-opening polymerization of 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) following with ally epoxidation of MAC units. After covalent bonding with laccase, the resulting HPC-PMAC-Laccase could assemble in aqueous solution to form spherical nanoparticles with an enzyme immobilization efficiency of 88%. The immobilized laccase showed more tolerance towards pH and high temperature compared with free laccase. Moreover, the immobilized laccase demonstrated effective removal efficiency of bisphenol A and reached 83% in 3 h. After repeated usage for 8 times, the HPC-PMAC-Laccase still maintained relatively high enzyme activity. Especially, the polycarbonates brushes in the enzyme carriers could be totally hydrolyzed in 12 h to achieve its degradable property.
Graphical abstractCellulose-based functional polycarbonates as degradable enzyme carriers.
How to improve the flame retardancy of lyocell fibers has become an important issue in textile industry. Herein, lyocell fibers were firstly undergone etherification reaction between sodium chloroacetate and the hydroxyl groups of lyocell fibers to obtain carboxymethylated lyocell fibers (CM-lyocell), then the sodium ions of CM-lyocell were replaced by aluminum ions, and the flame retardant lyocell fibers (FR-lyocell) were prepared. Compared with lyocell fibers, the degradation temperature of FR-lyocell decreased by about 80 °C, and the char residue in nitrogen increased from 15.1 to 31.8 wt% at 800 °C. Importantly, the limiting oxygen index (LOI) value of FR-lyocell fabric was increased from 17.2 to 26.4%. Besides, the peak of heat release rate (PHRR) and total heat release (THR) of FR-lyocell had 77.4% and 76.3% reduction, respectively. The FR-lyocell can generate a highly graphitized char layer and release more water at high temperatures, which are beneficial to improving the flame retardancy of lyocell fibers. Moreover, the tensile test showed that the tensile strength of FR-lyocell decreased from 3.95 to 3.08 cN/dtex with a 22% reduction, showing good strength retention.
Graphic abstractEucalyptus cellulose is usually pre-treated by oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), NaBr and NaClO at pH 10.5 and 25 °C before the mechanical process required to obtain cellulose nanofibers (CNFs). In this study, different aspects to improve the effectiveness and sustainability of the TEMPO-mediated oxidation are analyzed. The optimization was carried out at different reaction times by modifying both the concentration of the NaClO and the amount of the catalysts (TEMPO and NaBr). Results show that the carboxyl groups increased up to 1.1 mmol/g with 5 mmol NaClO/g after 50 min, and that the catalyst concentration can be reduced to 0.025 mmol TEMPO/g and 0.5 mmol NaBr/g to minimize costs while maintaining the high fibrillation degree of the CNFs. The kinetic of the reaction can be considered as zero-order with respect to NaClO, and as first order with respect to cellulose. As a result of this work, the catalyst doses are reduced up to 75% compared to the most widely used catalyst doses (0.1 mmol/g TEMPO and 1 mmol/g NaBr), obtaining highly fibrillated CNFs with a lower environmental impact. This reduction of catalyst doses will reduce the costs and facilitate the implementation of CNF production at industrial scale.
Graphical abstractCellulose nanocrystals (CNCs) with high crystallinity exhibit high mechanical stiffness and strength. However, the high dispersibility of CNCs results in limited spinnability and orientation. In this study, oxidized nanocellulose was selected to obtain regionally oxidized CNCs (RO-CNC) with carboxyl groups appended. For the formation of orientable and extensible RO-CNC filaments, chitosan was introduced as the sheath solution to induce orientation by electrostatic action. The chemical structures were analyzed by Fourier transform infrared spectroscopy. The morphology of the oriented CNCs filaments was characterized by scanning electron microscopy and wide-angle X-ray scattering. Analysis of the relationship between the mechanical strength and the CNCs directional arrangement revealed that the mechanical strength of the composite fibers increased with the injection speed ratio as a result of the orientation of the RO-CNC. The mechanical strength of the oriented reinforced composite filaments reached as high as 104 MPa with an orientation index of 0.73. The tensile strength and elastic modulus of the filaments increased by 33% and 20%, respectively, compared to the unmodified CNCs spun fiber.
Graphic abstractOceans and soils have been contaminated with traditional plastic due to its lack of degradability. Therefore, green biopolymer composites reinforced with cellulose nanocrystal-zinc oxide hybrids (ZnO hybrids) with good biodegradation ability provided a positive impact on reducing environmental challenges. In this work, the effect of various morphologies of ZnO hybrids on the biodegradation ability of poly(butylene adipate-co-terephthalate), PBAT) under seawater, soil burial, and UV aging conditions were investigated. Sheet-like ZnO hybrids (s-ZnO hybrid) efficiently enhanced the mechanical, UV-blocking properties and biodegradation ability of PBAT nanocomposite films. Compared to neat PBAT, the best tensile strength of PBAT nanocomposite with 2 wt% s-ZnO hybrid was increased by 15.1%, meanwhile this nanocomposite films showed the highest biodegradation rate after 80 days of soil degradation and 90 days of seawater degradation. Besides, three possible biodegradation mechanisms of green PBAT nanocomposite films were presented, hinting that such PBAT nanocomposite have great promising packaging applications.
Graphic abstractCaesalpinia sappan L. wood fiber (CSWF), a novel advanced bio-reinforcement for polybutylene succinate (PBS) composite films, has shown significant promise ranging from 0 to 15 part per hundred of resin (phr). The functional groups and interactions, morphology, thermal stability, mechanical characteristics, and biodegradability were all investigated. Without treatment or any compatibilizers, CSWF could be well-dispersed in the PBS matrix. The PBS/CSWF10 composite film had highest mechanical strength, with a tensile strength of 12.21 N/mm2 and a break elongation of 21.01%. Biodegradability studies indicated that the PBS/CSWF10 composite films degraded completely in three months. Furthermore, the Ea of degradation resulting from TGA and the shift of wavenumber resulting from FTIR revealed that the addition of CSWF has a greater interaction between additive and martix than conventional cellulose. The PBS/CSWF10 composite has the potential to be environmentally friendly, with promising short-term degradation and rising mechanical characteristics. Therefore, it is the optimum concentration of a certain biocomposite film. As a result, a novel advanced natural-based cellulose for biopolymer composites film was discovered, as well as other benefits for bio-reinforcement of the green plastic composite film industry.
Graphical abstractLife-threatening diseases, especially those caused by pathogens and harmful ultraviolet radiation (UV-R), have triggered increasing demands for comfortable, antimicrobial, and UV-R protective clothing with a long service life. However, developing such textiles with exceptional wash durability is still challenging. Herein, we demonstrate how to fabricate wash durable multifunctional cotton textiles by growing in situ ZnO-TiO2 hybrid nanocrystals (NCs) on the surface of cellulosic fabrics. The ZnO-TiO2 hybrid NCs presented high functional efficiency, owing to their high charge transfer/separation. Ultrafine fiber surface pores, utilized as nucleating sites, endowed the uniform growth of NCs and their physical locking. The resulting fabrics presented excellent UV protection factors up to 54, displayed bactericidal efficiency of 100% against Staphylococcus aureus and Escherichia coli, and optimum self-cleaning efficacy. Moreover, the functionalized textiles exhibited robust washing durability, maintaining antibacterial and anti-UV-R efficiency even after 30 extensive washing cycles.
Graphical abstractActivated carbon paper-based materials were prepared from softwood pulp, activated carbon powder, and polyester fiber through wet forming process. Then polyethyleneimine was loaded on the activated carbon paper-based materials using physical impregnation method to fabricate green, low cost, and degradable PEI/activated carbon composite paper-based adsorbent materials (PPCA) for the removal of Cr(VI) from drinking water. The surface characteristics of the adsorbent were analyzed by SEM, EDX, BET, FT-IR, and XPS. It was found that the maximum adsorption capacity of Cr(VI) could reach up to 1.58 mg g?1 when the PEI immersion concentration is 1%, the contact time is 180 min, the temperature is 30 °C and pH?=?2. The adsorption of Cr(VI) on PPCA conformed to both the freundlich isotherm model and the quasi-second-order kinetic model, indicating that the adsorption was multi-molecular layer adsorption controlled by chemical reaction process. The adsorption mechanism of Cr(VI) on PPCA included electrostatic attraction, redox and chelation. Overall, this study provides a green, large-scalable production way for the preparation of biodegradable adsorption materials for the efficient removal of Cr(VI) from drinking water aiding the safe management of aqueous system.
Graphical abstractA variety of liquid energy exists in papermaking engineering and has not yet been developed and utilized. In addition, for the papermaking industry, the presence of slime can seriously affect the quality of the finished paper and can lead to paper breaking. The current slime control strategies cannot completely solve the problem and also have some low toxicity. In this study, a method of self-powered sterilization of cellulose fibers by using triboelectric pulsed direct current is reported. A liquid–solid triboelectric nanogenerator (L–S TENG) was used to convert the liquid energy of nanocellulose suspension into electrical energy and convert this electrical energy into pulsed direct current for self-powered sterilization of cellulose fiber. A hydrophobic coating material is used as solid triboelectric material and electrode for sterilization. Driven by L–S TENG, the electrodes exhibited an excellent sterilization rate against four microorganisms including Escherichia coli, Aspergillus niger, Candida albicans, and Klebsiella pneumoniae, which from slime in the papermaking industry. This study could provide a basic research theory for liquid energy harvesting in the papermaking industry, and also provide a new strategy for pulp sterilization.
Graphical abstractMillions of tons of fruit waste are generated globally every year from agricultural residues, which makes it essential to find alternative uses to increase their aggregate value and reduce their environmental impact. The present study aimed to explore pineapple peel as an alternative source of cellulose by evaluating its chemical composition and physical properties, which are essential for applications. A sequence of chlorine-free treatments was applied to purify the cellulose by removing noncellulosic components in the fresh pineapple peels. The cellulosic pulp was characterized regarding its chemical composition and characterized by Nuclear Magnetic Resonance (13C NMR), X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to determine crystallinity, structural properties, morphology, and thermal characteristics, respectively. The results revealed that the pineapple peel amorphous segments containing hemicelluloses and lignin were extensively removed with increasing chemical treatment steps, leading to increased purity, crystallinity index, and thermal stability of the extracted cellulose pulps. The maximum thermal degradation (150 °C) and crystallinity index (80.9%) were determined for the cellulosic material obtained from the second bleaching (2B) step. The cellulose content increased from 24% in the starting material (fresh pineapple peel) to 80.9% in the bleached cellulose (2B). These results indicate that the extracted cellulose from pineapple peel has characteristic for applications such as the production of cellulose nanocrystals due to the high crystallinity.
Graphical abstract