Conductive hybrid filaments of carbon nanotubes, chitin nanocrystals and cellulose nanofibers formed by interfacial nanoparticle complexation

In this paper, anionic TEMPO-oxidized cellulose nanofibers (TO-CNFs) and cationic, partially deacetylated, chitin nanocrystals (ChNCs) were used to fabricate continuous composite filaments (TO-CNF/ChNC filament) with a straightforward and sustainable aqueous process based on the interfacial nanoparticle complexation (INC) of oppositely charged nano-constituents. In particular, the role of TO-CNF and ChNC concentrations in filament drawing and the effect of drawing speed on the mechanical properties of composite filaments were investigated. Moreover, conductive filaments were fabricated by mixing single walled carbon nanotubes (SWCNTs) with TO-CNF dispersion and further complexing with the ChNC aqueous suspension. A conductive filament with an electrical conductivity of 2056 S/m was obtained. However, the increase in the SWCNTs content reduced the mechanical properties of the formed filament compared to neat TO-CNF/ChNC filament. This study not only introduces a new nanoparticle candidate to prepare filaments based on INC method but also provides potential advanced and alternative green filament to be used as wearable electronics in biomedical area

Self-assembly of graphene oxide and cellulose nanocrystals into continuous filament via interfacial nanoparticle complexation

The present work demonstrates the spinning of conductive filaments from oppositely charged nano-scale entities, i.e., cationic cellulose nanocrystals (CNC) and anionic graphene oxide (GO), via interfacial nanoparticle complexation. Especially, the role of CNC and GO concentration in filament formation was investigated. Moreover, the chemical structure, morphology and composition of formed CNC/GO composite filaments were further characterized. The positively charged CNC formed firstly a complex film with negatively charged GO flake and then the complexed structures were further assembled into macroscale hybrid filament (diameter about 20 to 50 μm). After chemical reduction of the hybrid filament, conductive filaments with an average tensile strength of 109 ± 8 MPa and electrical conductivity of 3298 ± 167 S/m were obtained. The presented approach provides a new pathway to understand the interaction of GO and nanocellulose, and to design macroscopic, assembled and functionalized architectures of GO and nanocellulose composites

Silylated thiol-containing cellulose nanofibers as a bio‑based flocculation agent for ultrafine mineral particles of chalcopyrite and pyrite

A considerable amount of very fine particles can be found, e.g., stored in tailing ponds, and they can include valuable or hazardous minerals that have the potential to be recovered. Selective flocculation, i.e., the formation of larger aggregates from specific minerals, offers a promising approach to improve the recovery of ultrafine particles. This study focuses on the use of a new bio-based flocculation agent made of silylated cellulose nanofibers containing a thiol-functional moiety (SiCNF). Flocculation was performed in separated systems of ultrafine mineral dispersions of pyrite, chalcopyrite, and quartz in aqueous alkaline medium. The flocculation performance of SiCNF was addressed in terms of the turbidity reduction of mineral dispersions and the floc size, and the results were compared with the performance of a commercial anionic polyacrylamide. SiCNF exhibited a turbidity removal efficiency of approximately 90%–99% at a concentration of 4000–8000 ppm with chalcopyrite and pyrite, whereas the turbidity removal of quartz suspension was significantly lower (a maximum of approximately 30%). The sulfide particles formed flocs with a size of several hundreds of micrometers. The quartz in turn did not form any visible flocs, and the dispersion still had a milky appearance after dosing 12,000 ppm of the flocculant. These results open a promising path for the investigation of SiCNF as a selective flocculation agent for sulfide minerals

High-performance and sustainable aerosol filters based on hierarchical and crosslinked nanofoams of cellulose nanofibers

Nano-structured and porous foams derived from crosslinked cellulose nanofibers (CNF) were designed and tailored as highly efficient aerosol filters. The lignin-containing CNF was prepared from a recycled milk-container board using deep eutectic solvent pretreatment and mechanical grinding. The nanofoams or aerogels were formed in different densities (initial CNF concentration of 0.2–1.0 wt%) with a freeze-drying process using two silane compounds for strengthening the structure. The filtration performance of nanofoams was studied with a Differential Mobility Particle Sizer (DMPS) setup using 10–500 nm NaCl aerosol particles. DMPS determines particle number size distribution of particles passing through nanofoams which is used to calculate the filtration performance. All nanofoams, which possessed porosity from 99.1% to 99.8% and specific surface area from 5.9 m2 g−1 to 18.6 m2 g−1, achieved good filtration performance (>96%) in the measured particle size range. Very high filtration efficiency (>99.5%) was achieved with the 0.7 wt% nanofoam sample for particles smaller than 360 nm. Based on the quality factors (QF), 0.3 wt% nanofoam produced the lowest pressure drop yet with relatively high filtration efficiency and resulted in the highest QF value that met the N95 standard requirements of respirator face masks. The structure and thickness of the nanofoam filter makes possible high particle bearing without loss on its performance.Peer reviewe

Impacts of offshore oil spill accidents on island bird communities: A test run study around Orkney and Svalbard archipelagos

The sea area around the Orkney archipelago, Scotland is subjected to substantial maritime shipping activities. By contract, the Svalbard archipelago, Norway currently has a rather low marine traffic profile. Future projections, however, indicate that the Trans-Arctic route might change the whole transportation picture and Svalbard may be at the centre of maritime activities. Both archipelagos have sensitive environmental resources at sea and inland, including bird communities. There are, for instance, 13 Red Listed species present in Orkney and 2 in Svalbard. In this regard, it is important to address oil spill risks along existing and projected shipping routes. Hypothetical spills were simulated in twelve scenarios for both the Orkney and Svalbard archipelagos with the OpenDrift open-source software. The results indicate risks to seabird communities. For Orkney, the spills resulted in the most extensive contamination of the sea and land environments in autumn. For Svalbard, autumn spills on the contrary presented the lowest risk to seabirds. Based on the simulations, we recommend increased caution for shipping activities in the problematic seasons, improved local readiness for ship accidents and sufficient preincident planning

Enrichment of bovine milk-derived extracellular vesicles using surface-functionalized cellulose nanofibers

The isolation of extracellular vesicles (EVs) from milk, a complex mixture of colloidal structures having a comparable size to EVs, is challenging. Although ultracentrifugation (UC) has been widely used for EV isolation, this has significant limitations, including a long processing time at high g-force conditions and large sample volume requirements. We introduced a new approach based on nature nanoentities cellulose nanofibers (CNFs) and short time and low g-force centrifugation to isolate EVs from various milk fractions. The flexible and entangled network of CNFs forms nanoporous, which entraps the EVs. Further, positively charged CNFs interact with anionic EVs through an electrostatic attraction, promoting their isolation with efficiency comparable with UC. The functionality and toxicity of isolated milk EVs were tested in Caco2 cells. Overall, the newly developed approach provides straightforward isolation and biocompatibility and preserves the natural properties of the isolated EVs, enabling further applications

Interactions between fibres, fines and fillers in papermaking:influence on dewatering and retention of pulp suspensions

Abstract Interactions between the components of papermaking suspensions (e.g. fibres, fillers, fines and polymers) have a remarkable effect on various unit processes in papermaking. The filterability of fibre suspensions, which is a crucial property for example in paper sheet forming and solid recovery, is also known to be depended on particle interactions. However, due to the complex nature of the interactions, the role of these phenomena in fibre suspension filtration is still not fully understood. The focus of this thesis was to find out how phenomena associated to fibre flocculation, fibre deflocculation and filler particle deposition affect the filterability of fibre suspensions in terms of their dewaterability and retention. It was shown that the influence of fibre flocculation on dewatering is closely related to the structure of fibre flocs. More importantly, the internal density of flocs and factors that impacted the packing structure of filter cakes, such as floc size, played a crucial role in fibre suspension dewaterability. Dense flocs with a low internal porosity particularly induces fast water flow by a mechanism termed as the “easiest path mechanism” through the large voids around the flocs. The effect of fibre suspension dispersing on dewaterability and particularly fines retention was found to be associated to the mechanism of action of the deflocculation agent. Carboxymethylcellulose (CMC), the deflocculant used in this study, had detrimental effects on the dewatering of a pulp suspension both when being adsorbed on fibre surfaces and when remained in the liquid phase. However, adsorbed CMC causes more plugging of the filter cake because it disperses the fines more profoundly. Thus the adsorbed CMC also reduces fines retention considerably more than CMC did in the liquid phase. Filler deposition and retention was found to be significantly higher on pulp fines fractions of mechanical and chemical pulp than on fibre fractions due to the higher external surface area of fines. The surface charge densities of pulp fractions also affected their ability to adsorb fillers. Cationic charges of filler particles was in turn observed to induce deposition of fillers on fibre surfaces which increased retention but also the dewaterability of a fibre suspension due to a decrease in total surface area of a suspension