Charged nanocellulose (NC) with a high aspect ratio (larger than 100) extracted from animal or bacterial cellulose and chemical cross-linked NC aerogels have great promising applicability in material science, but facile fabrication of such NC aerogels from plant cellulose by physical cross-linking still remains a major challenge. In this work, carboxylated cellulose nanofiber (CNF) with the highest aspect ratio of 144 was extracted from wasted ginger fibers by a simple one-step acid hydrolysis. Our approach could easily make the carboxylated CNF assemble into robust bulk aerogels with tunable densities and desirable shapes on a large scale (3D macropores to mesopores) by hydrogen bonds. Excitingly, these CNF aerogels had better compression mechanical properties (99.5 kPa at 80% strain) and high shape recovery. Moreover, the CNF aerogels had strong coagulation-flocculation ability (87.1%), removal efficiency of MB dye uptake (127.73 mg/g), and moderate Cu absorption capacity (45.053 mg/g), which were due to assistance mechanisms of charge neutralization, network capture effect, and chain bridging of high aspect ratio carboxylated CNF. This provided a novel physical cross-linking method to design robust aerogels with modulated networked structures to be a general substrate material for industrial applications such as superabsorbent, flocculation, oil-water separation, and potential electrical energy storage materials.

Nature employs supramolecular self-assembly to organize many molecularly complex structures. Based on this, we now report for the first time the supramolecular self-assembly of 3D lightweight nanocellulose aerogels using carboxylated ginger cellulose nanofibers and polyaniline (PANI) in a green aqueous medium. A possible supramolecular self-assembly of the 3D conductive supramolecular aerogel (SA) was provided, which also possessed mechanical flexibility, shape recovery capabilities, and a porous networked microstructure to support the conductive PANI chains. The lightweight conductive SA with hierarchically porous 3D structures (porosity of 96.90%) exhibited a high conductivity of 0.372 mS/cm and a larger areanormalized capacitance (C s ) of 59.26 mF/cm 2 , which is 20 times higher than other 3D chemically cross-linked nanocellulose aerogels, fast charge−discharge performance, and excellent capacitance retention. Combining the flexible SA solid electrolyte with low-cost nonwoven polypropylene and PVA/H 2 SO 4 yielded a high normalized capacitance (C m ) of 291.01 F/g without the use of adhesive that was typically required for flexible energy storage devices. Furthermore, the supramolecular conductive aerogel could be used as a universal sensitive sensor for toxic gas, field sobriety tests, and health monitoring devices by utilizing the electrode material in lightweight supercapacitor and wearable flexible devices.

Cellulose is the most abundant renewable natural polymer on earth, but it does not conduct electricity, which limits its application expansion. The existing methods of making cellulose conductive are combined with another conductive material or high-temperature/high-pressure carbonization of the cellulose itself, while in the traditional method of sulfuric acid hydrolysis to extract nanocellulose, it is usually believed that a too high temperature will destroy cellulose and lead to experimental failure. Now, based on a new research perspective, by controlling the continuous reaction process and isolating oxygen, we directly extracted intrinsically conductive cellulose nanofiber (CNF) from biomass, where the confined range molecular chains of CNF were converted to highly graphitized carbon at only 90 °C and atmospheric pressure, while large-scale twisted graphene films can be synthesized bottom-up from CNFene suspensions, called CNFene (cellulose nanofiber–graphene). The conductivity of the best CNFene can be as high as 1.099 S/cm, and the generality of this synthetic route has been verified from multiple biomass cellulose sources. By comparing the conventional high-pressure hydrothermal and high-temperature pyrolysis methods, this study avoided the dangerous high-pressure environment and saved 86.16% in energy. These findings break through the conventional notion that nanocellulose cannot conduct electricity by itself and are expected to extend the application potential of pure nanocellulose to energy storage, catalysis, and sensing.

A simple and eco-friendly Fe2+/H2O2 oxidation of microcrystalline celluloses (MCCs) to prepare cellulose nanocrystals (CNCs) with high carboxylation content is proposed. The effects of reaction times on the morphology, microstructure, and chemical and thermal properties of isolated carboxylated CNCs were investigated. The oxidative decomposition of Fe2+/H2O2 solution of MCC yielded CNCs with a size of 92–140 nm in length and 19–23 nm in width. The CNCs extracted at 6 h possessed the highest carboxyl content (2.2 mmol/g) with a zeta potential of −41 mV and a thermal decomposition temperature of greater than 325 °C. These CNCs are efficient adsorbents for dyes (methylene blue) and metal ions (copper ion) found in wastewater, with removal rates of up to 95.6 and 82.3%, respectively.

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Water hyacinth was used as substrate for bioethanol production in the present study. Combination of acid pretreatment and enzymatic hydrolysis was the most effective process for sugar production that resulted in the production of 402.93 mg reducing sugar at optimal condition. A regression model was built to optimize the fermentation factors according to response surface method in saccharification and fermentation (SSF) process. The optimized condition for ethanol production by SSF process was fermented at 38.87°C in 81.87 h when inoculated with 6.11 ml yeast, where 1.291 g/L bioethanol was produced. Meanwhile, 1.289 g/L ethanol was produced during experimentation, which showed reliability of presented regression model in this research. The optimization method discussed in the present study leading to relatively high bioethanol production could provide a promising way for Alien Invasive Species with high cellulose content.

In outdoor activities and disaster environments, a portable microdevice is very important for the rapid purification of field drinking water. Smart cryogels were fabricated by one-pot copolymerization among acrylamide (AM) monomers, 2-(dimethylamino) ethyl methacrylate (DMAEMA) monomers, and cellulose nanocrystal/zinc oxide (CNC/ZnO) nanorod clusters through a simple ice-template method. The effect of nanohybrid contents on microstructural, thermal, swelling, and antibacterial properties of cryogels-ZnO was investigated. With the incorporation of 1 wt % CNC/ZnO, the cryogels showed macroporous-networked structures with a high porosity of 93% and homogeneous nanorod clusters on the macroporous wall. Cryogels-ZnO showed high mechanical strength in both dry and wet states, an adsorption capacity of 30.8 g/g, superfast adsorption time (2.5 s), and a stable swelling−deswelling ability after 10 cycles. Additionally, the adsorption capacity of cryogels-ZnO presented a dual temperature/pH response. Upon treatment of the simulated field water with cryogels-ZnO for 45 min, the cfu amounts of simulated field water were decreased from 1862 to 6 cfu/mL. This cfu amount for treated water was much lower than the 100 cfu/mL of China's national drinking water standard. In addition, cryogels-ZnO can effectively handle 14.3−16.1 g/g of disinfected drinking water by manual compression. Such cryogels-ZnO exhibited a great potential for field drinking-water-purifying microdevices.