Evaluation of Aerogel Spheres Derived from Salix psammophila in Removal of Heavy Metal Ions in Aqueous Solution

Heavy metal wastewater treatment is a huge problem facing human beings, and the application degree of Salix psammophila resources produced by flat stubble is low. Therefore, it is very important to develop high-value products of Salix psammophila resources and apply them in the removal heavy metal from effluent. In this work, we extracted the cellulose from Salix psammophila, and cellulose nanofibers (CNFs) were prepared through TEMPO oxidation/ultrasound. The aerogel spheres derived from Salix psammophila (ASSP) were prepared with the hanging drop method. The experimental results showed that the Cu(II) adsorption capacity of the ASSP composite (267.64 mg/g) doped with TOCNF was significantly higher than that of pure cellulose aerogel spheres (52.75 mg/g). The presence of carboxyl and hydroxyl groups in ASSP enhanced the adsorption capacity of heavy metals. ASSP is an excellent heavy metal adsorbent, and its maximum adsorption values for Cu(II), Mn(II), and Zn(II) were found to be 272.69, 253.25, and 143.00 mg/g, respectively. The abandoned sand shrub resource of SP was used to adsorb heavy metals from effluent, which provides an important reference value for the development of forestry in this sandy area and will have a great application potential in the fields of the adsorption of heavy metals in soil and antibiotics in water.

A Fast-Response Electroactive Actuator Based on TEMPO-Oxidized Cellulose Nanofibers

Cellulose-based electroactive actuators are promising candidates for biomimetic robots and biomedical applications due to their lightweight, high mechanical strength, and natural abundance. However, cellulose-based electroactive actuators exhibit lower actuation performance than traditional conductive polymer actuators. This work reports a fast-response cellulose-based electroactive actuator based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized nanocellulose (TOCNF) film with layered structure fabricated by evaporation, and gold electrodes prepared by ion sputtering. The residual ions during the TEMPO oxidation process and the layered structure due to self-assembly accelerate the ion migration efficiency in actuators. The proposed actuator can reach a tip displacement of 32.1 mm at a voltage of 10 V and deflect 60° in 5 s. After applying a reverse 10 V voltage, the actuator can also be quickly deflected (42.5 mm). In addition, the actuator also shows high electrical actuation performance at low voltage (5 V). The excellent electroactive performance of as-prepared TOCNF/Au enables the feasibility to be applied to actuators.

Bacteria-engineered porous sponge for hemostasis and vascularization

Background Hemostasis and repair are two essential processes in wound healing, yet early hemostasis and following vascularization are challenging to address in an integrated manner. Results In this study, we constructed a hemostatic sponge OBNC-DFO by fermentation of Acetobacter xylogluconate combined with TEMPO oxidation to obtain oxidized bacterial nanocellulose (OBNC). Then angiogenetic drug desferrioxamine (DFO) was grafted through an amide bond, and it promoted clot formation and activated coagulation reaction by rapid blood absorption. The further release of DFO stimulated the secretion of HIF-1α and the reconstruction of blood flow, thus achieving rapid hemostasis and vascularization in damaged tissue. This new hemostatic sponge can absorb approximately 38 times its weight in 28 seconds, rapidly enhancing clot formation in the early stage of hemostasis. In vitro and in vivo coagulation experiments (in rat tail amputation model and liver trauma model) demonstrated superior pro-coagulation effects of OBNC and OBNC-DFO to clinically used collagen hemostatic sponges (COL). They promoted aggregation and activation of red blood cells and platelets with shorter whole blood clotting time, more robust activation of endogenous coagulation pathways and less blood loss. In vitro cellular assays showed that OBNC-DFO prevailed over OBNC by promoting the proliferation of human umbilical vein endothelial cells (HUVECs). In addition, the release of DFO enhanced the secretion of HIF-1α, further strengthening vascularization in damaged skin. In the rat skin injury model, 28 days after being treated with OBNC-DFO, skin appendages (e.g., hair follicles) became more intact, indicating the achievement of structural and functional regeneration of the skin. Conclusion This hemostatic and vascularization-promoting oxidized bacterial nanocellulose hemostatic sponge, which rapidly activates coagulation pathways and enables skin regeneration, is a highly promising hemostatic and pro-regenerative repair biomaterial.

Evaluation of mulberry branch waste as raw material for nanocellulose synthesis: effects of the synthesis method on product properties

The mechanical pulp of mulberry branches was evaluated as a raw material for the production of cellulose II and its subsequent conversion to nanocellulose via high-pressure homogenization, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidation, and sulfuric acid hydrolysis. The morphology, chemical structure, crystallinity, and thermal stability of the nanocellulose samples prepared by each method were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and thermogravimetric analysis. The results showed that nanocellulose prepared by high-pressure homogenization exhibited higher aspect ratio (>100), and the weight loss peak in the DTG chart was 361 °C, with the best thermal stability, whereas that prepared by sulfuric acid hydrolysis featured shorter fiber length (96±31 nm) and a higher crystallinity (78.2 %).The TEMPO oxidized nanocellulose (TOCN) had smaller width (5.5±1.6 nm) and high carboxyl content (1.5 mmol/g). In addition, we have further studied the application of TOCN in the wet end of papermaking, replacing the colloidal SiO2 in CPAM/ colloidal SiO2/APAM retention system with the same amount (3600 ppm) of TOCN. The study found that the strength of the paper obtained by adding TOCN instead of the traditional wet end additives is similar, and the water drainage and retention properties of the pulp are improved.

Scalable Preparation of Cellulose Nanofibers from Office Waste Paper by an Environment-Friendly Method

Waste paper is often underutilized as a low-value recyclable resource and can be a potential source of cellulose nanofibers (CNFs) due to its rich cellulose content. Three different processes, low acid treatment, alkali treatment and bleaching treatment, were used to pretreat the waste paper in order to investigate the effect of different pretreatments on the prepared CNFs, and CNFs obtained from bleached pulp boards were used as control. All sample fibers were successfully prepared into CNFs by 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) oxidation. It was quite obvious that the bleached CNFs samples showed dense fibrous structures on a scanning electron microscopy (SEM), while needle-like fibers with width less than 20 nm were observed on a transmission electron microscopy (TEM). Meanwhile, the bleaching treatment resulted in a 13.5% increase in crystallinity and a higher TEMPO yield (e.g., BCNF, 60.88%), but a decrease in thermal stability. All pretreated CNFs samples showed narrow particle size distribution, good dispersion stability (zeta potential less than −29.58 mV), good light transmission (higher than 86.5%) and low haze parameters (lower than 3.92%). This provides a good process option and pathway for scalable production of CNFs from waste papers.

Scaled Synthesis of Polyamine-Modified Cellulose Nanocrystals from Bulk Cotton and Their Use for Capturing Volatile Organic Compounds

We have previously demonstrated that cellulose nanocrystals modified with poly(ethylenimine) (PEI-f-CNC) are capable of capturing volatile organic compounds (VOCs) associated with malodors. In this manuscript, we describe our efforts to develop a scalable synthesis of these materials from bulk cotton. This work culminated in a reliable protocol for the synthesis of unmodified cellulose nanocrystals (CNCs) from bulk cotton on a 0.5 kg scale. Additionally, we developed a protocol for the modification of the CNCs by means of sequential 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidation and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling to modify their surface with poly(ethylenimine) on a 100 g scale. Subsequently, we evaluated the performance of the PEI-f-CNC materials that were prepared in a series of VOC capture experiments. First, we demonstrated their efficacy in capturing volatile fatty acids emitted at a rendering plant when formulated as packed-bed filter cartridges. Secondly, we evaluated the potential to use aqueous PEI-f-CNC suspensions as a spray-based delivery method for VOC remediation. In both cases, the PEI-f-CNC formulations reduced detectable malodor VOCs by greater than 90%. The facile scaled synthesis of these materials and their excellent performance at VOC remediation suggest that they may emerge as a useful strategy for the remediation of VOCs associated with odor.

Novel pretreatment performance evaluation for cellulose nanofibrils extraction from Ficus natalensis barkcloth

Recently, nanosized cellulose materials extraction is extensively interesting from the sources of sustainable materials. Cellulose nanofibrils (CNF) extraction through green bio-based materials featured as promising interest in the field of science. In this study, dimethyl sulfoxide (DMSO) was applied to examine its effectiveness in pretreating the Ficus natalensis barkcloth cellulose (FNBC) for CNF production perior to 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO) oxidation. The pretreatment performance of DMSO was evaluated based on the structural and morphological changes. DMSO pretreated FNBC attained the most dramatic morphological changes as compared to untreated cellulose samples. The results of scanning electron microscope (SEM) and transmission electron microscope (TEM) shows that there is an extentive structural disruption of FNBC during the pretreatment process, could be because of outstanding ability to eliminate non-cellulosic materials and amorphous regions from the FNBC, confirmed by the X-ray diffractometry (XRD) showing higher crystallinity values as well as higher thermal stablilites values of pretreated FNBC samples were also noted. Overall, this study revealed tremendously effective and pioneer pretreatment method for fractionating FNBC, to stimulate the successive extraction of cellulose nanofibrils. Furthermore, on the basis of the cellulose and CNF characterizations, this study showed that Ficus natalensis barkcloth could be considered as an alternative source of cellulose for potential value-added industrial applications such as food industry, paper making, and biomedicines.

TEMPO-oxidized cellulose hydrogel for efficient adsorption of Cu 2+ and Pb 2+ modified by PEI

In this study, hydrogel were prepared by dissolving and regenerating poplar-cellulose in NaOH/urea/water system. The TEMPO-oxidized cellulose hydrogels (TCH) were prepared using microwave-assisted accelerated TEMPO-oxidation system. Polyethyleneimine (PEI) was grafted onto TCH with glutaraldehyde as a cross-linking agent and the products named as TCP. The hydrogels were characterized by SEM, FTIR, XPS and elemental analyzer. The maximum adsorption capacities of Cu2+ and Pb2+ by TCP were 109.89 mg/g and 279.32 mg/g, respectively. TCP was a single molecule adsorption process with better fitting of Langmuir model. Adsorption kinetics showed that the Pb2+ adsorption rate of TCP was higher than that for Cu2+. The Cu2+ affinity of TCP was higher than the Pb2+. The adsorption capacity of TCP for Cu2+ and Pb2+ was 58.26 mg/g and 91.96 mg/g, respectively, after five cycles. This study provided a promising option of preparing an efficient and recyclable adsorbent in treating wastewater containing heavy metal, such as Cu2+ and Pb2+.