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From an economic and environmental perspective, the use of less chemicals in the production of cellulose nanofibrils (CNFs) is advantageous. In this study, we investigated the oxidation (TEMPO/NaClO 2 /NaClO, pH 6.8) of softwood (SW) particles with varying amounts of TEMPO (16, 8 or 0 mg g -1 of wood). Following, TEMPO-oxidized SW nanofibrils (TO-SWNFs) were obtained by nanofibrillation and their size, morphology, and crystallite size were assessed. Hydrogel networks of TO-SWNFs were prepared and mechanical properties were measured in dH 2 O and phosphate buffered saline (PBS) to compare their performance for possible biomedical applications such as wound dressings. The results reveal that the presence of TEMPO is of importance for TO-SWNF network properties, presenting higher eq. H 2 O absorption (≈2500 %) and elongation at break (≈10 %) with good wet strength (≈180 kPa). In addition, a decrease in use of TEMPO catalyst from 16 to 8 mg g -1 of wood is possible, without detrimental effects on hydrogel network properties (dH 2 O absorption ≈ 2000 %, elongation at break ≈ 13 %, wet strength ≈ 190 kPa) related to applications as wound dressings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The self-assembly of nanocellulose in the form of cellulose nanofibers (CNFs) can be accomplished via hydrogen-bonding assistance into completely bio-based hydrogels. This study aimed to use the intrinsic properties of CNFs, such as their ability to form strong networks and high absorption capacity and exploit them in the sustainable development of effective wound dressing materials. First, TEMPO-oxidized CNFs were separated directly from wood (W-CNFs) and compared with CNFs separated from wood pulp (P-CNFs). Second, two approaches were evaluated for hydrogel self-assembly from W-CNFs, where water was removed from the suspensions via evaporation through suspension casting (SC) or vacuum-assisted filtration (VF). Third, the W-CNF-VF hydrogel was compared to commercial bacterial cellulose (BC). The study demonstrates that the self-assembly via VF of nanocellulose hydrogels from wood was the most promising material as wound dressing and displayed comparable properties to that of BC and strength to that of soft tissue.

Considering the growing use of cellulose in various applications, knowledge and understanding of its physical properties become increasingly important. Thermal conductivity is a key property, but its variation with porosity and density is unknown, and it is not known if such a variation is affected by fiber size and temperature. Here, we determine the relationships by measurements of the thermal conductivity of cellulose fibers (CFs) and cellulose nanofibers (CNFs) derived from commercial birch pulp as a function of pressure and temperature. The results show that the thermal conductivity varies relatively weakly with density (ρ sample = 1340-1560 kg m -3 ) and that its temperature dependence is independent of density, porosity, and fiber size for temperatures in the range 80-380 K. The universal temperature and density dependencies of the thermal conductivity of a random network of CNFs are described by a third-order polynomial function (SI-units): κ CNF = (0.0787 + 2.73 × 10 -3 · T - 7.6749 × 10 -6 · T 2 + 8.4637 × 10 -9 · T 3 )·(ρ sample /ρ 0 ) 2 , where ρ 0 = 1340 kg m -3 and κ CF = 1.065·κ CNF . Despite a relatively high degree of crystallinity, both CF and CNF samples show amorphous-like thermal conductivity, that is, it increases with increasing temperature. This appears to be due to the nano-sized elementary fibrils of cellulose, which explains that the thermal conductivity of CNFs and CFs shows identical behavior and differs by only ca. 6%. The nano-sized fibrils effectively limit the phonon mean free path to a few nanometers for heat conduction across fibers, and it is only significantly longer for highly directed heat conduction along fibers. This feature of cellulose makes it easier to apply in applications that require low thermal conductivity combined with high strength; the weak density dependence of the thermal conductivity is a particularly useful property when the material is subjected to high loads. The results for thermal conductivity also suggest that the crystalline structures of cellulose remain stable up to at least 0.7 GPa.

In this study, ginger residue from juice production was evaluated as a raw material resource for preparation of nanofiber hydrogels with multifunctional properties for advanced wound dressing applications. Alkali treatment was applied to adjust the chemical composition of ginger fibers followed by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation prior to nanofiber isolation. The effect of alkali treatment on hydrogel properties assembled through vacuum filtration without addition of any chemical cross-linker was evaluated. An outstanding absorption ability of 6200% combined with excellent mechanical properties, tensile strength of 2.1 ± 0.2 MPa, elastic modulus of 15.3 ± 0.3 MPa, and elongation at break of 25.1%, was achieved without alkali treatment. Furthermore, the absorption capacity was tunable by applying alkali treatment at different concentrations and by adjusting the hydrogel grammage. Cytocompatibility evaluation of the hydrogels showed no significant effect on human fibroblast proliferation in vitro. Ginger essential oil was used to functionalize the hydrogels by providing antimicrobial activity, furthering their potential as a multifunctional wound dressing.

The aim of this study was to fabricate a novel bilayer scaffold containing cellulose nanofiber/poly (vinyl) alcohol (CNF/PVA) to evaluate its potential use in skin tissue engineering. Here, the scaffolds were fabricated using a novel one-step freeze-drying technique with two different concentrations of the aforementioned polymers. FE-SEM analysis indicated that the fabricated scaffolds had interconnected pores with two defined pore size in each layer of the bilayer scaffolds that can recapitulate the two layers of the dermis and epidermis of the skin. Lower concentration of polymers causes higher porosity with larger pore size and increased water uptake and decreased mechanical strength. FTIR proved the presence of functional groups and strong hydrogen bonding between the molecules of CNF/PVA and the efficient crosslinking. The MTT assay showed that these nanofibrous scaffolds meet the requirement as a biocompatible material for skin repair. Here, for the first time, we fabricated bilayer scaffold using a novel one-step freeze-drying technique only by controlling the polymer concentration with spending less time and energy., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Multifunctional lightweight, flexible, yet strong polymer-based nanocomposites are highly desired for specific applications. However, the control of orientation and dispersion of reinforcing nanoparticles and the optimization of the interfacial interaction still pose substantial challenges in nanocellulose-reinforced polymer composites. In this study, poly(ethylene glycol) (PEG)-grafted cellulose nanofibers have demonstrated much better dispersion in a poly(lactic acid) (PLA) matrix as compared to unmodified nanocellulose. Through a uniaxial drawing method, aligned PLA/nanocellulose nanocomposites with high strength, high toughness, and unique optical behavior can be obtained. With the incorporation of 0.1 wt % of the PEG-grafted cellulose nanofibers in PLA, the ultimate strength of the aligned nanocomposite reaches 343 MPa, which is significantly higher than that of other aligned PLA-based nanocomposites reported previously. Moreover, its ultimate strength and toughness are enhanced by 39% and 70%, respectively, as compared to the aligned nanocomposite reinforced with unmodified cellulose nanofibers. In addition, the aligned nanocomposite film is highly transparent and possesses an anisotropic light scattering effect, revealing its significant potential for optical applications.

When aiming for higher resource efficiency, greater utilization of waste streams is needed. In this work, waste paper separated from mixed municipal solid waste (MSW) was studied as a potential starting material for the production of cellulose nanofibres (CNFs). The waste paper was treated using three different techniques, namely pulping, flotation and washing, after which it was subjected to an ultrafine grinding process to produce CNFs. The energy consumption of the nanofibrillation and nanofibre morphology, as well as properties of the prepared nanofibers, were analysed. Despite the varying amounts of impurities in the waste fibres, all samples could be fibrillated into nanoscale fibres. The tensile strengths of the CNF networks ranged from 70 to 100 MPa, while the stiffness was ∼7 GPa; thus, their mechanical strength can be adequate for applications in which high purity is not required. The contact angles of the CNF networks varied depending on the used treatment method: the flotation-treated networks were more hydrophilic (contact angle 52.5°) and the washed networks were more hydrophobic (contact angle 72.6°)., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Microorganisms can spread on the surface of banknotes and cause many infectious diseases. Chitosan nanofibers (CNFs) and cellulose nanocrystals (CNCs) are nanomaterials, which can affect the antimicrobial properties. In this study, the fungal species that grew on the surfaces of collected banknotes from different places were identified. To examine the antifungal effect of the both nanomaterials on the banknotes, the stable coatings using CNFs and CNCs emulsions were prepared by roller coating. The results revealed that the most colonies in the banknotes obtained from the bakeries and butcheries were Aspergillus sp., whereas the colonies in bus terminals and the hospitals were Aspergillus niger and Penicillium, respectively. The results showed that the CNCs had no antifungal effect alone on the aforementioned species, but it could improve the antifungal effect, adhesion, and stability of CNFs on the banknote surfaces. This study suggested a new approach to decrease the infection spreads through banknotes., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

TEMPO-mediated oxidized cellulose nanofibers (TOCNFs) have shown potential in the bioremediation of metal ions from contaminated water due to their interaction with positively charged metal ions via electrostatic interactions involving surface carboxyl groups. Copper is one of the most common pollutants in industrial effluents and is thus the target metal in the current study. The specific surface adsorption of Cu(II) was similar for TOCNFs with different degrees of functionalization and directly impacted the zeta potential. SEM imaging of the TOCNF after Cu(II) adsorption revealed interesting nanostructured clusters that were attributable to Cu(II) ions first being adsorbed by carboxylate groups on the TOCNF and subsequently being reduced and self-assembled to Cu(0) nanoparticles (NPs) or copper oxide NPs by microprecipitation. TOCNF turned superhydrophilic and resulted in faster water filtration after copper adsorption due to the stronger polarity of the copper ions or the self-assembled Cu(0) NPs creating voids or highly water-permeable channels at the interface between the interconnected TEMPO-oxidized nanofibers. Thus, the adsorption of Cu(II) ions and self-assembly into the Cu NPs on TOCNF favors a faster water purification process and provides a viable route to reuse/recycle TOCNFs studded with Cu nanoparticles as biocidal materials., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The potential of nanoscaled cellulose and enzymatically phosphorylated derivatives as bio-adsorbents to remove metal ions (Ag(+), Cu(2+) and Fe(3+)) from model water and industrial effluents is demonstrated. Introduction of phosphate groups onto nanocelluloses significantly improved the metal sorption velocity and sorption capacity. The removal efficiency was considered to be driven by the high surface area of these nanomaterials as well as the nature and density of functional groups on the nanocellulose surface. Generally, in the solutions containing only single types of metal ions, the metal ion selectivity was in the order Ag(+)>Cu(2+)>Fe(3+), while in the case of mixtures of ions, the order changed to Ag(+)>Fe(3+)>Cu(2+), irrespective of the surface functionality of the nanocellulose. In the case of industrial effluent from the mirror making industry, 99% removal of Cu(2+) and Fe(3+) by phosphorylated nanocellulose was observed. The study showed that phosphorylated nanocelluloses are highly efficient biomaterials for scavenging multiple metal ions, simultaneously, from industrial effluents., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We demonstrated that low-cost and environmentally friendly filaments of native cellulose can be prepared by dry spinning an aqueous suspension of cellulose nanofibers (CNF). The CNF were extracted from banana rachis, a bioresidue from banana cultivation. The relationship between spinning rate, CNF concentration, and the mechanical properties of the filaments were investigated and the results showed that the modulus of the filaments was increased from 7.8 to 12.6 GPa and the strength increased from 131 to 222 MPa when the lowest concentration and highest speed was used. This improvement is believed to be due to an increased orientation of the CNF in the filament. A minimum concentration of 6.5 wt % was required for continuous filament spinning using the current setup. However, this relatively high concentration is thought to limit the orientation of the CNF in the filament. The process used in this study has a good potential for upscaling providing a continuous filament production with well-controlled speed, but further work is required to increase the orientation and subsequently the mechanical properties.

Bio-based fibrous nanocomposites of cellulose nanofibres and non-crosslinked/crosslinked collagen were prepared by in situ pH-induced fibrillation of collagen phase and sterilized using gamma rays at 25 KGy. Collagen phase is crosslinked using genipin, a bio-based crosslinker that introduces flexible crosslinks. Microscopy studies of the prepared materials showed nanostructured fibrous collagen and cellulose dispersed in collagen matrix. Mechanical performance of the sterilized nanocomposites was close to that of natural ligament and tendon, in simulated body conditions. Cytocompatibility studies indicated that these nanocomposites allowed human ligament cell and human endothelial cell adhesion, growth, and differentiation; which is eminently favourable to ligament tissue engineering., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The structural changes of the glucopyranose chain and the chemical compositional response of cellulose nanofibers (CNFs) under thermal exposure (at 190 °C for 5 h) have remained a significant gap in the understanding of the long-term performance of nanocellulose. Herein, CNF films with different chemical compositions were investigated to confirm the structural transformation of glucopyranose (coupling constant of OH groups changed up to 50%) by nuclear magnetic resonance (NMR) analysis. Remarkably, the glucopyranose rings underwent partial dehydration during the thermal exposure resulting in enol formation. This study confirms the chain mobility that could lead to the conformational and dimensional changes of the CNFs during thermal exposure. The broad range of conformations was defined by the dihedral angles that varied from ±27° to ±139° after thermal exposure. Investigation into the mechanism involving chemical transformation of the substrates during heating is important for the fabrication of the next generation of flexible electrical materials. [ABSTRACT FROM AUTHOR]

In this study, the effect of pectin extraction method on the properties of cellulose nanofibers (CNFs) isolated from sugar beet pulp (SBP) was studied. Pectin was extracted by the industrially practiced method by sulfuric acid hydrolysis or by enzymatic hydrolysis using a cellulase/xylanase enzymes mixture. The CNFs were then isolated by high-pressure homogenization and investigated in terms of their chemical composition, crystallinity, size, degree of polymerization, and re-dispersion in water after freeze-drying. The mechanical properties and surface characteristics of CNF films were also studied. The results showed that fibrillation of the de-pectinated SBP was more efficient for the acid hydrolyzed SBP. CNFs from the acid-hydrolyzed SBP had a slightly wider diameter, higher crystallinity, viscosity, and α-cellulose content but a lower degree of polymerization than CNFs from the enzyme-hydrolyzed SBP. Owing to the presence of more residual hemicelluloses in the CNFs from the enzyme-hydrolyzed SBP, the CNFs had higher re-dispersion ability in water. CNF films from enzyme-hydrolyzed SBP displayed slightly better mechanical properties and higher water contact angle than acid-hydrolyzed CNF films. [ABSTRACT FROM AUTHOR]

There has been an increasing interest in recent years in isolating cellulose nanofibers from unbleached cellulose pulps for economic, environmental, and functional reasons. In the current work, cellulose nanofibers isolated from high-lignin unbleached neutral sulfite pulp were compared to those isolated from bleached rice straw pulp in making thin-film ultrafiltration membranes by vacuum filtration on hardened filter paper. The prepared membranes were characterized in terms of their microscopic structure, hydrophilicity, pure water flux, protein fouling, and ability to remove lime nanoparticles and purify papermaking wastewater effluent. Using cellulose nanofibers isolated from unbleached pulp facilitated the formation of a thin-film membrane (with a shorter filtration time for thin-film formation) and resulted in higher water flux than that obtained using nanofibers isolated from bleached fibers, without sacrificing its ability to remove the different pollutants. [ABSTRACT FROM AUTHOR]

The link between wood and corresponding cellulose nanofiber (CNF) behavior is complex owing the multiple chemical pretreatments required for successful preparation. In this study we apply a few pretreatments on aspen wood and compare the final CNF behavior in order to rationalize quantitative studies of CNFs derived from aspen wood with variable properties. This is relevant for efforts to improve the properties of woody biomass through tree breeding. Three different types of pretreatments were applied prior to disintegration (microfluidizer) after a mild pulping step; derivatizing TEMPO-oxidation, carboxymethylation and non-derivatizing soaking in deep-eutectic solvents. TEMPO-oxidation was also performed directly on the plain wood powder without pulping. Obtained CNFs (44–55% yield) had hemicellulose content between 8 and 26 wt% and were characterized primarily by fine (height ≈ 2 nm) and coarser (2 nm < height < 100 nm) grade CNFs from the derivatizing and non-derivatizing treatments, respectively. Nanopapers from non-derivatized CNFs had higher thermal stability (280 °C) compared to carboxymethylated (260 °C) and TEMPO-oxidized (220 °C). Stiffness of nanopapers made from non-derivatized treatments was higher whilst having less tensile strength and elongation-at-break than those made from derivatized CNFs. The direct TEMPO-oxidized CNFs and nanopapers were furthermore morphologically and mechanically indistinguishable from those that also underwent a pulping step. The results show that utilizing both derivatizing and non-derivatizing pretreatments can facilitate studies of the relationship between wood properties and final CNF behavior. This can be valuable when studying engineered trees for the purpose of decreasing resource consumption when isolation cellulose nanomaterials. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of high water retention by cellulose nanofibers (CNFs) that lead to exorbitant time consumption in the dewatering of CNF suspensions. This has been a bottleneck, which is restricting the commercialization of CNF derived products such as nanopapers and CNF reinforced paper sheets. As a remedy, we suggest an eco-friendly water-based approach that involves the use of sonication energy and lactic acid (LA) to modify the surface of CNFs. The suggested modification resulted in rapid water drainage, and dewatering was completed in 10 min; with unmodified CNFs, it took around 45 min. We have also compared the draining characteristics of LA modification of CNF suspensions with a common draining agent (NaCl); LA modification drains water 56% faster than the use of NaCl, and produced mechanically superior dimensionally stable nanopaper. Additionally, LA modification allows the addition of 10 wt.% CNF in paper sheets, with dewatering done in 2 min (while the unmodified CNFs took 23 min). [ABSTRACT FROM AUTHOR]

Abstract: There is a recent interest in producing cellulose nanofibers with different surface properties from unbleached cellulose pulps for economic and environmental reasons. In the current study we investigated the use of xylanase pretreatment on two types of unbleached rice straw pulps, namely, soda and neutral sulfite, and their fibrillation to nanofibers using ultrafine grinding. The effect of xylanase pretreatment on the fibrillation progress, energy consumption, and nanofiber dimensions was studied. In addition, mechanical properties, water contact angle, water absorption, and roughness of produced nanopapers were studied. Although very thin nanofibers with a homogenous width could be isolated from both xylanase-treated and untreated pulps, the xylanase pretreatment resulted in faster fibrillation. In addition, nanopapers prepared from xylanase-treated nanofibers had better mechanical properties than those isolated from the untreated pulps. The energy consumption during fibrillation depended on the type of pulp; a slightly lower energy consumption (~ 8%) was recorded for xylanase-treated soda pulp while a higher energy consumption (~ 21%) was recorded for xylanase-treated neutral sulfite pulp compared to the untreated pulps.Graphical Abstract: [ABSTRACT FROM AUTHOR]

ABSTRACT The present study deals with the processing and characterization of cellulose nanocomposites natural rubber (NR), low-density polyethylene (LDPE) reinforced with carrot nanofibers (CNF) with the semi-interpenetrated network (S-IPN) structure. The nanocomposites were compounded using a co-rotating twin-screw extruder where a master-batch of NR and CNF was fed to the LDPE melt, and the NR phase was crosslinked with dicumyl peroxide. The prepared S-IPN nanocomposites exhibited a significant improvement in tensile modulus and yield strength with 5 wt % CNF content. These improvements are due to a better phase dispersion in the S-IPN nanocomposites compared with the normal blend materials, as demonstrated by optical microscopy, electron microscopy and ultraviolet-visible spectroscopy. The S-IPN nanocomposite also displayed an improved crystallinity and higher thermal resistance compared with NR, CNF, and the normal blend materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45961. [ABSTRACT FROM AUTHOR]

Metallo-terpyridine compounds and polymers exhibit unique optical, electrical, magnetic and antimicrobial properties. Recently, metallo-terpyridine-modified cellulosic films with interesting porous structure, that exhibit these properties, have been prepared. Herein we report the use of Cu-terpyridine-modified oxidized cellulose nanofibers (OXCNF-Cu-Tpy) as membranes for treatment of effluents of paper mills to produce re-usable water. The OXCNF-Cu-Tpy was prepared by modification of TEMPO-oxidized CNF (OXCNF) using copper(II) complex of 4′-Chloro [2,2′:6′,2″] terpyridine. The modification was proven by elemental analysis and Fourier transform infrared spectroscopy. The prepared OXCNF-Cu-Tpy was also characterized using X-ray diffraction and transmission electron microscopy. The prepared membranes were evaluated regarding their microscopic structure using scanning electron microscopy, atomic force microscopy, contact angle measurement, water flux and rejection of sub-micron size suspended particles in papermaking wastewater effluent. Chemical modification of OXCNF with the Cu-Tpy groups significantly increased pure water flux of the membranes by about 52 and 194% depending on pressure used during filtration (0.5 and 1 MPa, respectively). Although both OXCNF and OXCNF-Cu-Tpy exhibited high efficiency in removing the sub-micron size suspended particles from wastewater effluent, OXCNF-Cu-Tpy membranes showed about 30% higher flux rate than OXCNF membranes. [ABSTRACT FROM AUTHOR]

The current work reports a novel, completely water based approach to prepare the water resistant modified cellulose nanopapers. Lactic acid in aqueous medium was attached on cellulose nanofibers surface with the aid of ultra-sonication and later oligomerized (polymerized) by compression molding under high temperature and pressure, to obtain the modified nanopapers with enhanced mechanical properties. The modified nanopapers showed an increase of 32% in the elastic modulus and 30% in the yield strength over reference nanopapers. Additionally, the modified nanopaper was hydrophobic in nature and had superior storage modulus under moist conditions. The storage modulus of wet modified nanopaper was three times (2.4 GPa) compared to the reference nanopapers (0.8 GPa) after 1 h immersion in water. Finally, the thermal stability of the modified nanopaper was also higher than reference nanopaper. The material reported is 100% bio-based. [ABSTRACT FROM AUTHOR]

Never-dried bacterial cellulose (BC) and crosslinked cellulose nanofibers (CNF) were used for the removal of oil from stabilized and non-stabilized oil-in-water emulsions with droplet sizes less than 1 μm. The CNF membranes were exchanged with isopropyl alcohol before drying. The microscopic structure of the prepared membranes was evaluated using scanning electron microscopy (SEM); the water flux and the rejection of oil were evaluated using a dead-end filtration cell. BC harvested after different incubation time periods (2 to 10 days) did not show a change in the width of the nanofibers, but only the thickness of the membranes was increased. Pure water flux was not affected as a result of increasing thicknesses of BC membranes harvested after 4-10 days while BC harvested after two days had significantly higher water flux than the others. BC showed a higher flux and efficiency in removing oil from oil emulsions than CNF membranes. Removal of oil by the different membranes from the non-stabilized oil emulsion was more efficient than from the stabilized one. [ABSTRACT FROM AUTHOR]

Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation. [ABSTRACT FROM AUTHOR]

Cellulosic nanomaterials are potential candidates in different areas, especially in water treatment. In the current work, palm fruit stalks cellulose nanofibers (CNF), TEMPO-oxidized CNF (OCNF), and activated carbon (AC) were used to make thin film membranes for removal of E. coli bacteria from water. Two types of layered membranes were produced: a single layer setup of crosslinked CNF and a two-layer setup of AC/OCNF (bottom) and crosslinked CNF (up) on hardened filter paper. The prepared membranes were evaluated regarding their microstructure and layers thickness using scanning electron microscopy (SEM). Water flux and rejection of E. coli bacteria was tested using dead end stirred cells at 1 MPa pressure. Thickness of the cosslinked CNF layer in both types of membranes was about 0.75 micron. The results showed that exchanging water by isopropyl alcohol before drying increased porosity of membranes, and thus resulted in increasing pure water flux and flux of bacteria suspension. The two-layer AC/OCNF/CNF membrane had much higher water flux than the single layer CNF due to higher porosity seen on the surface of the former. Both types of membranes showed high capability of removing E. coli bacteria (rejection ~96-99%) with slightly higher efficiency for the AC/OCNF/CNF membrane than CNF membrane. AC/OCNF/CNF membrane also showed resistance against growth of E. coli and S. aureus bacteria on the upper CNF surface while the single layer CNF membrane did not show resistance against growth of the aforementioned bacteria. [ABSTRACT FROM AUTHOR]

A simple method for preparing redispersible nanofibers from sugar beet residue and their use as a well-dispersed reinforcement for a polyvinyl alcohol (PVA) matrix is reported. It is known that the redispersion of dried cellulose nanofibers is difficult because of the formation of strong hydrogen bonds between the nanofibers. The results show that the properties of the initial sugar beet nanofiber suspension can be recovered without the use of chemical modification or additives with higher pectin and hemicellulose content. Undried and redispersed nanofibers with and without pectin were used as nanocomposite reinforcement with PVA. The redispersed nanofibers were as good reinforcements as the undried nanofibers. The tensile strength and elastic modulus of the nanocomposites with the redispersed sugar beet nanofibers were as good as those of the nanocomposites with undried nanofibers. Interestingly, the nanofiber dispersion in the PVA matrix was better when sugar beet nanofibers containing pectin and hemicellulose were used as reinforcements. [ABSTRACT FROM AUTHOR]

The separation of nanofibers from carrot juice residue and their reinforcing potential is demonstrated. Morphological properties, X-ray diffraction (XRD), and specific surface area (SSA) measurements showed that carrot nanofibers (CNF) have maintained the crystalline structure of native cellulose, while presenting a SSA as high as 246 m 2 .g −1 and diameters between 3 and 36 nm. CNF could be redispersed in water after drying, giving nanofibers with SSA and diameter comparable to properties of initial never-dried CNF. Finally, we propose possible uses of CNF either as strong nanopaper with excellent mechanical properties, i.e. modulus of 13.3 GPa and strength of 175 MPa, or as reinforcing phase in polymer matrices (CAB). Interesting properties of carrot nanofibers in terms of their possible transport and use from the dry state, as well as their remarkable mechanical properties afforded to nanopaper and nanocomposites may promote their use in environmentally benign constituent in industrial applications. [ABSTRACT FROM AUTHOR]

Bio-based continuous fibers were prepared by melt spinning cellulose acetate butyrate (CAB), cellulose nanocrystals (CNC) and triethyl citrate. A CNC organo-gel dispersion technique was used and the prepared materials (2 and 10 wt% CNC) were melt spun using a twin-screw micro-compounder and drawn to a ratio of 1.5. The microscopy studies showed that the addition of CNC in CAB resulted in defect-free and smooth fiber surfaces. An addition of 10 wt% CNC enhanced the storage modulus and increased the tensile strength and Young's modulus. Fiber drawing improved the mechanical properties further. In addition, a micromechanical model of the composite material was used to estimate the stiffness and showed that theoretical values were exceeded for the lower concentration of CNC but not reached for the higher concentration. In conclusion, this dispersion technique combined with melt spinning can be used to produce all-cellulose nanocomposites fibers and that both the increase in CNC volume fraction and the fiber drawing increased the mechanical performance. [ABSTRACT FROM AUTHOR]

ABSTRACT The efficiency of twin-screw extrusion process to fibrillate cellulose fibers into micro/nanosize in the same step as the compounding of green bionanocomposites of thermoplastic starch (TPS) with 10 wt % fibers was examined. The effect of the processing setup on micro/nanofibrillation and fiber dispersion/distribution in starch was studied using two types of cellulose fibers: bleached wood fibers and TEMPO-oxidized cellulose fibers. A composite with cellulose nanofibers was prepared to examine the nanofiber distribution and dispersion in the starch and to compare the properties with the composites containing cellulose fibers. Optical microscopy, scanning electron microscopy, and UV/Vis spectroscopy showed that fibers were not nanofibrillated in the extrusion, but good dispersion and distribution of fibers in the starch matrix was obtained. The addition of cellulose fibers enhanced the mechanical properties of the TPS. Moisture uptake study revealed that the material containing TEMPO-oxidized fibers had higher moisture absorption than the other composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39981. [ABSTRACT FROM AUTHOR]

The study explores the potential of cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and chitin nanocrystals (ChNC) isolated from bioresidues to remove silver ions from contaminated water. Zeta sizer studies showed negatively charged surfaces for CNC and CNF isolated from cellulose sludge in the acidic and alkaline pHs, whereas ChNC isolated from crab shell residue showed either positive or negative charges depending on pH conditions. Model water containing silver ions showed a decrease in Ag ion concentration (measured by inductively coupled plasma-optical emission spectrometer; inductively coupled plasma mass spectrometry), after treatment with CNC, CNF and ChNC suspensions. The highest Ag ion removal was measured near neutral pH for CNC, being 34.4 mg/g, corresponding to 64 % removal. ChNC showed 37 % and CNF showed 27 % removal of silver ions. The WDX (wavelength dispersive X-ray analysis) and XPS (X-ray photoelectron spectroscopy) analysis confirmed the presence of silver ions on the surface of the nanocellulose and nanochitin after adsorption. Surface adsorption on the nanoparticles via electrostatic interactions is considered to be the prominent mechanism of heavy metal ion capture from aqueous medium, with CNC with negative surface charge and negatively charged functional groups being most favourable for the adsorption of positively charged Ag ions compared to other native bionanomaterials. [ABSTRACT FROM AUTHOR]

The properties of cellulose/polypropylene (PP) nanocomposites with n-octadecyl-modified bagasse nanofibers (MBNF) were compared to those with maleated polypropylene (MAPP) coupling agent. The nanocomposites were prepared by twin-screw extrusion with bagasse nanofiber (BNF) content varying from 2.5 to 10 wt%. The compression molded nanocomposites sheets were characterized regarding their tensile strength properties, dynamic mechanical thermal properties, crystallinity, water absorption, transparency and loss of strength due to composting in soil. As a compatibilizer to improve the tensile strength properties and transparency of PP/cellulose nanofibers nanocomposites, MAPP was more effective than n-octadecyl-modified cellulose nanofibers. The crystallinity of the nanocomposites was lower than that of neat PP except for those prepared using high loading of MBNF. Dynamic mechanical thermal analysis (DMTA) of the prepared materials showed that adding the different nanofibers (treated or untreated) resulted in better mechanical thermal properties above glass transition temperature (Tg) of PP. Water absorption capability in all nanocomposites was weakened while that in PP/MBNF was the lowest. No significant differences were found between the nanocomposites with different kinds of nanofibers regarding the loss of their tensile strength after compositing in soil up to six months. [ABSTRACT FROM AUTHOR]

The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5 wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones. [ABSTRACT FROM AUTHOR]

Nanofibers were isolated from rice straw pulp using ultrahigh friction grinding and high-pressure homogenization. Chitosan nanocomposites were prepared using the isolated nanofibers at fiber loading from 2.5 to 20% by solution casting and evaporation technique. The effect of nanofiber loading on dry and wet tensile strength, dynamic mechanical thermal properties, and cyrstallinity of chitosan were studied using tensile testing, thermogravimetric analysis, dynamic mechanical thermal analysis, and X-ray diffraction. Addition of rice straw nanofibers (RSNF) to chitosan resulted in significant improvement in wet and dry tensile strength, and shift of glass transition temperature ( T g) of chitosan matrix to higher values. Chitosan nanocomposites prepared using RSNF (CRSNF) had remarkable wet and dry tensile strength, which could be attributed to presence of both nanofibers and nanosilica particles originally present in rice straw fibers. Addition of RSNF to chitosan did not affect its onset thermal degradation temperature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Nanocomposites were prepared using two bioresources, viz., cellulose nanofibers (CNFs) extracted from bamboo paper-pulp waste as the reinforcing phase and natural rubber (NR) as the matrix phase. CNFs with diameters up to 50 nm were isolated from bamboo pulp waste, and nanocomposites with 5 and 10% CNFs were obtained via two-roll mill mixing of solid natural rubber with a master batch containing 20 wt% CNFs. The NR phase was cross-linked using sulphur vulcanization. The morphology studies showed that the dispersion of CNF in NR matrix was not optimal, and some aggregates were visible on the fracture surface. The tensile strength and modulus at 50% elongation increased for the nanocomposites with the addition of CNFs, accompanied by a moderate decrease in elongation at break. The storage modulus of the natural rubber significantly increased above its glass-rubber transition temperature upon nanofiber addition. The addition of CNFs also had a synergistic impact on the thermal stability of natural rubber. The susceptibility to organic solvents decreased significantly for the nanocomposites compared to crosslinked NR, which indicated restriction of polymer chain mobility in the vicinity of the nanosized CNFs in the NR matrix. [ABSTRACT FROM AUTHOR]

This article investigates the transport behavior of three aromatic organic solvents, viz. benzene, toluene, and p-xylene in natural rubber nanocomposite membranes containing cellulose nanofibres (CNFs) and cellulose nanowhiskers (CNWs) isolated from bamboo pulp. The solvent molecules act as molecular probes to study the diffusion, sorption, and permeation through the nanocomposites, and provide information on the nanocomposite structure and matrix-filler interactions. Both the nanocelluloses were found to decrease the uptake of aromatic solvents in nanocomposite membranes, but the effect was more significant in the case on nanofibers compared to nanowhiskers. Furthermore, the uptake decreased with increased penetrant size; being the highest for benzene and the lowest for p-xylene. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated. Comparison of the experimental values of equilibrium solvent uptake with the predicted values indicated that both the nanocelluloses have restricted the molecular mobility at the interphase and thereby decreased the transport of solvents through the materials; being more significant for nanofibers. The results showed that both the used cellulosic nanomaterials act as functional additives capable of manipulating and tailoring the transport of organic solvents through elastomeric membranes, even at concentrations as low as 2.5 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Collagen and cellulose nanofiber based composites were prepared by solution casting followed by pH induced in situ partial fibrillation of collagen phase and crosslinking of collagen phase using gluteraldehyde. Microscopy studies on the materials confirmed the presence of fibrous collagen and cellulose nanofibers embedded in the collagen matrix. The cellulose nanofiber addition as well as collagen crosslinking showed significant positive impact on the nanocomposite's mechanical behaviour. The synergistic performance of the nanocomposites indicated stabilization and reinforcement through strong physical entanglement between collagen and cellulose fibres as well as chemical interaction between collagen matrix and collagen fibrils. The mechanical performance and stability in moist conditions showed the potential of these materials as implantable scaffolds in biomedical applications. The collagen-cellulose ratio, crosslinking agent and crosslinking level of collagen may be further optimised to tailor the mechanical properties and cytocompatibility of these composites for specific applications such as artificial ligament or tendon. [ABSTRACT FROM AUTHOR]

Nanofibers (NF) were isolated from bleached bagasse and rice straw pulps. The pulps were refined using high-shear ultrafine grinder and then homogenized using high-pressure homogenizer. The efficiency of the used isolation processes was studied by optical microscopy (OM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and testing the tensile properties (wet and dry) of nanopaper sheets made from the nanofibers. In addition, opacity and porosity of nanopaper sheets made after different processing steps were investigated. The microscopy studies showed that the processes used resulted in nanofibers with diameters ranging from 3.5 to 60 nm. The results indicated that main isolation of nanofibers took place during refining using the ultrafine grinding process, while high-pressure homogenization resulted in smaller and more homogeneous size of nanofibers. Nanopaper sheets made from bagasse showed better wet and dry tensile strength properties than those made of rice straw. [ABSTRACT FROM AUTHOR]

In the present study, chemical-physical properties of nanofibers isolated from rubberwood ( Hevea brasiliensis) and empty fruit bunches (EFB) of oil palm ( Elaeis guineensis) were analyzed by microscopic, spectroscopic, thermal and X-ray diffraction methods. The isolation was achieved using chemo-mechanical processes. Microscopy study showed that the diameters of the nanofibers isolated from the EFB ranged from 5 to 40 nm while those of the nanofibers isolated from rubberwood had a wider range (10-90 nm). Fourier transform infrared spectroscopy study demonstrated that almost all the lignin and most of the hemicellulose were removed during the chemical treatments. X-ray diffraction analysis revealed that the crystallinity of the studied nanofibers increased after the chemo-mechanical isolation process. The results of thermogravimetric analysis showed that the nanofibers isolated from both sources had higher thermal stability than those of the bleached pulp and untreated fibers. [ABSTRACT FROM AUTHOR]

Bleached bagasse pulp was pretreated with dilute alkali and xylanase enzymes before isolation of microfibrillated cellulose using ultra-high friction grinding and high-pressure homogenization. The isolated nanofibers were used with chitosan polymer to prepare chitosan nanocomposites by solution casting at nanofiber loading from 2.5 to 20%. The effect of nanofibers loading on moisture sorption, dry and wet tensile strength, crystallinity, thermal stability, and dynamic mechanical thermal properties was studied using tensile testing, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). Nanocomposites with good transparency were obtained at the different nanofibers loadings. Chitosan nanocomposites made using nanofibers isolated from bagasse fibers treated with xylanase or alkali showed higher dry and wet tensile strength than those made using nanofibers isolated from untreated bagasse pulp. DMTA results showed higher storage modulus and indicated higher glass transition temperature for the chitosan nanocomposites than that of neat chitosan. XRD patterns showed that, at low nanofibers loading, addition of bagasse nanofibers to chitosan matrix increased ordering of chitosan chains upon drying the nanocomposites films. [ABSTRACT FROM AUTHOR]

The article reports that two kinds of nanocelluloses, including mechanically isolated nanofibers (CNF) and acid-hydrolyzed nonwhiskers (CNW), have been extracted from softwood flour. It states that the aqueous suspensions of both nanocelluloses formed strong gels at low solid content, which showed independence of dynamic moduli on frequency. It mentions that it is possible that the extracted cellulose was partly dissolved and regenerated during acid hydrolysis.

In addition to their lower cost and more environmentally friendly nature, cellulose nanofibers isolated from unbleached pulps offer different surface properties and functionality than those isolated from bleached pulps. At the same time, nanofibers isolated from unbleached pulps keep interesting properties such as hydrophilicity and mechanical strength, close to those isolated from bleached pulps. In the current work, rice straw nanofibers (RSNF) isolated from unbleached neutral sulfite pulp (lignin content 14%) were used with polysulfone (PSF) polymer to make membrane via phase inversion. The effect of RSNF on microstructure, porosity, hydrophilicity, mechanical properties, water flux, and fouling of PSF membranes was studied. In addition, the prepared membranes were tested to remove lime nanoparticles, an example of medium-size nanoparticles. The results showed that using RSNF at loadings from 0.5 to 2 wt.% can significantly increase hydrophilicity, porosity, water flux, and antifouling properties of PSF. RSNF also brought about an increase in rejection of lime nanoparticles (up to 98% rejection) from their aqueous suspension, and at the same time, with increasing flux across the membranes. Tensile strength of the membranes improved by ~29% with addition of RSNF and the maximum improvement was obtained on using 0.5% of RSNF, while Young's modulus improved by ~40% at the same RSNF loading. As compared to previous published results on using cellulose nanofibers isolated from bleached pulps, the obtained results in the current work showed potential application of nanofibers isolated from unbleached pulps for improving important properties of PSF membranes, such as hydrophilicity, water flux, rejection, and antifouling properties. [ABSTRACT FROM AUTHOR]

Nanofibers isolated from unbleached neutral sulfite rice straw pulp were used to prepare transparent films without the need to modify the isolated rice straw nanofibers (RSNF). RSNF with loading from 1.25 to 10 wt.% were mixed with cellulose acetate (CA) solution in acetone and films were formed by casting. The films were characterized regarding their transparency and light transmittance, microstructure, mechanical properties, crystallinity, water contact angle, porosity, water vapor permeability, and thermal properties. The results showed good dispersion of RSNF in CA matrix and films with good transparency and homogeneity could be prepared at RSNF loadings of less than 5%. As shown from contact angle and atomic force microscopy (AFM) measurements, the RSNF resulted in increased hydrophilic nature and roughness of the films. No significant improvement in tensile strength and Young's modulus was recorded as a result of adding RSNF to CA. Addition of the RSNF did not significantly affect the porosity, crystallinity and melting temperature of CA, but slightly increased its glass transition temperature. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to isolate cellulose nanofibers by ultrafine grinding, from sludge (residue from dissolving cellulose production) and cellulose (dissolving cellulose) and to characterize their properties. The mechanical fibrillation was found to be more energy efficient at low rotor speed (1440) and was estimated to be 1.7 and 1.3kWh/kg for cellulose (CF) and sludge fibers (SF), respectively. Sludge (SNF) and cellulose (CNF) nanofibers had diameter less than 100nm, as measured from transmission electron microscopy images. The specific surface area ranged from approximately 84 to 112m2/g for CNF and SNF respectively. The apparent networks density increased with fibrillation, being approximately 330 and 370 for CF and SF while 907 and 986kg/m3 for the corresponding nanosized ones. The scanning electron microscopy (SEM) study exhibited considerably smoother surfaces for the nanofiber networks compared to microsized. Fibrillation to nanosized fibers had positive impact on modulus and strength of both raw materials and the improvement was more significant for sludge, indicating more efficient fibrillation. The study showed that the isolation of nanofibers from sludge could be considered an economic, energy efficient and viable alternative to generate value-added product from cellulose sludge while minimizing the sludge disposal issues. [Copyright &y& Elsevier]

Conversion of bio-based industrial residues into high value-added products such as natural nanofibers is advantageous from an environmental and economic perspective, promoting resource efficiency along with the utilization of renewable materials. However, in order to employ the benefits of the raw material; its eco-efficient production should further be developed. Within this context, eco-design optimization through life cycle assessment (LCA) combined with life cycle costing (LCC) were applied to target eco-efficient production of natural nanofibers from carrot residue, along with quality assessment. The initial production steps included pretreatment combined mechanical nanofibrillation via ultrafine grinding, where the largest contributors to the environmental impact were identified as chemicals and energy. These were targeted by omitting the alkali pretreatment step and instead applying direct bleaching prior to nanofibrillation. After eco-design optimization, the yield increased while the energy, chemical, and water use significantly decreased. Therefore, a reduced environmental impact of more than 75% each for carbon footprint, freshwater ecotoxicity, and human toxicity was shown, along with a cost reduction of more than 50%. The use of carrot residue displayed an efficient conversion into natural nanofibers that was further promoted with the use of eco-design, yet with sustained functionality and nanoscaled dimensions, thus promoting resource-efficiency and natural nanofiber implementation in a wide range of promising bio-based applications. Image 1 • Eco-efficient production of high-quality natural nanofibers was demonstrated. • Eco-design optimization via LCA resulted in a 75% reduction of the carbon-footprint. • LCC revealed a 50% cost reduction after optimization of the processing route. • Higher yield by preservation of hemicellulose and pectin enhances efficiency. • An approach for efficient conversion combined waste minimization was presented. [ABSTRACT FROM AUTHOR]

Cellulose nanofiber aerogels were used as preforms that were impregnated with a bio-epoxy resin via a widely used vacuum infusion process. The simple and straightforward nanocomposite processing approach resulted in an almost 70% improvement in the storage modulus of the polymer with only an 11.7 wt% cellulose nanofiber content. The nanofibers were well dispersed in the polymer matrix and the fiber structures were anisotropically aligned. The impregnation time of the aerogels was also significantly lower than that of the more commonly used nanopapers. It was thus shown that environmentally friendly and mechanically robust nanocomposites could be produced by impregnating cellulose nanofiber aerogels with a thermosetting resin using a processing approach that has potential to be scaled up for commercial use. [ABSTRACT FROM AUTHOR]

In this study, the addition of hydroxyethyl cellulose (HEC) in cellulose nanofiber filaments is shown to improve the solvent-free processing and mechanical properties of these biobased fibers as well as their compatibility with epoxy. An aqueous dope of cellulose nanofiber (CNF) with HEC was spun and the resulting filaments cold-drawn. The HEC increased the wet strength of the dope allowing stable spinning of low concentrations of CNF. These lower concentrations promote nanofiber alignment which is further improved by cold-drawing. Alignment improves the modulus and strength and an increase of over 70% compared to the as-spun CNF only filaments was achieved. HEC also decreases hydrophilicity thus increasing slightly the interfacial shear strength of the filaments with epoxy resin. The result is continuous biobased fibers with improved epoxy compatibility that can be prepared in an upscalable and environmentally friendly way. Further optimization is expected to increase draw ratio and consequently mechanical properties. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the production potential of cellulose nanofibers from two different industrial bio-residues: wastes from the juice industry (carrot) and the beer brewing process (BSG). The mechanical separation of the cellulose nanofibers was by ultrafine grinding. X-ray diffraction (XRD) and Raman spectroscopy revealed that the materials were mechanically isolated without significantly affecting their crystallinity. The carrot residue was more easily bleached and consumed less energy during grinding, using only 0.9 kWh/kg compared to 21 kWh/kg for the BSG. The carrot residue also had a 10% higher yield than the BSG. Moreover, the dried nanofiber networks showed high mechanical properties, with an average modulus and strength of 12.9 GPa and 210 MPa, respectively, thus indicating a homogeneous nanosize distribution. The study showed that carrot residue has great potential for the industrial production of cellulose nanofibers due to its high quality, processing efficiency, and low raw material cost. [ABSTRACT FROM AUTHOR]

In this study, carrot nanofibers (CNF) were used to enhance the performance of biobased castor oil polyol polyurethane nanocomposite foams. A method of dispersing CNF in the polyol was developed and the foam characteristics and CNF reinforcing effect were studied. Co-solvent-assisted mixing resulted in well-dispersed CNF in the polyol, and foams with 0.25, 0.5 and 1 phr CNF content were prepared. The reinforced nanocomposite foams displayed a narrow cell size distribution and the compressive strength and modulus were significantly elevated and the best compressive strength and modulus were reached with 0.5 phr CNF. Similarly, the modulus of the solid material was also significantly increased based on theoretical calculations. When comparing the foam performance, compressive strength and stiffness as a function of the density, the nanocomposite foams performs as commercial rigid PU foam with a closed cell structure. These results are very promising and we believe that these foams are excellent core materials for lightweight sandwich composites. [ABSTRACT FROM AUTHOR]

Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers suspensions followed by dip coating with cellulose nanocrystals having sulphate or carboxyl surface groups. It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes via control of drying conditions and acetone treatment. Cellulose nanofibers coated with cellulose nanocrystal with carboxyl surface groups showed the highest tensile strength (95 MPa), which decreased in wet conditions (≈3.7 MPa) and with acetone (2.7 MPa) treatment. The membrane pore sizes, determined by nitrogen adsorption/desorption were in nanofiltration range (74 Å) and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194 Å) with a concomitant increase (7000%) of surface area. The water flux, also increased from zero to 25 L m −2 h −1 at a pressure differential of 0.45 MPa, for acetone treated membranes. Modeling of the permeance showed that the middle layer of cellulose nanofibers was responsible for the majority of the resistance to flux and the flux can be improved by increasing the porosity or decreasing the thickness of this layer. The membranes irrespective of the surface functionality showed exceptional capability (≈100%) to remove Ag + , Cu 2+ and Fe 3+ /Fe 2+ ions from mirror industry effluents. Surface adsorption followed by micro-precipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultrafiltration membranes with high rejection towards metal ions. [ABSTRACT FROM AUTHOR]