Cellulose nanomaterial (CNM) and polyethylenimine (PEI) composites have attracted growing attention due to their multifunctional characteristics, which have been applied in different fields. In this work, soybean hulls were valorized into carboxyl cellulose nanofibrils (COOH-CNFs), and composited into hydrogels with PEI by combining them with cationic chelating and physical adsorption strategies. Cellulose nanofibrils (CNFs) were produced from soybean hulls prior to oxidation by a TEMPO mediated reaction to obtain COOH–CNFs; then drops of zinc chloride were added to 1.5% aqueous COOH–CNF dispersions, which were left for 24 h to form COOH-CNF hydrogels. Finally, the hydrogels were functionalized using different concentration of PEI solutions over a range of pH values. Elemental analysis results showed that 20% aq. PEI at pH 11.6 is the optimum condition to synthesize the COOH–CNF/PEI hydrogels. Additionally, the adsorption efficiency for the removal of anionic methyl blue dyes and Cu(II) ions from water was tested, reaching 82.6% and 69.8%, respectively, after 24 h. These results demonstrate the great potential of COOH–CNF/PEI hydrogels as adsorbent materials for water remediation.
- Award ID(s):
- 2047762
- NSF-PAR ID:
- 10491272
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Cellulose
- Volume:
- 30
- ISSN:
- 0366-6816
- Page Range / eLocation ID:
- 3639-3651
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract Graphical abstract -
Cellulose nanofibrils (CNFs) produced through processes involving oxidation (e.g. TEMPO oxidation) present reactive groups that allow for straightforward modification in aqueous suspension. CNFs fabricated through mechanical refinement alone can be challenging to modify for subsequent reactions due to only having hydroxyl groups present on the surface. To address these issues, CNFs with only hydroxyl groups present were functionalized with norbornene groups in their native aqueous suspension to achieve up to 10% functionalization per anhydroglucose unit. Since quantification of surface functionalizationof CNFs is challenging through most methods, a degradation and subsequent nuclear magnetic resonance analysis method was developed to quantify norbornene functionalization. The norbornene functionalized CNFs (nCNFs) were crosslinked through UV and thermally initiated thiol-eneclick reactions to create robust CNF hydrogels. By varying the reaction conditions, hydrogels made from nCNFs and a dithiol cross-linker could achieve compression modulus values up to 25 kPa. The materials were stable in aqueous suspensions and the cross-linked hydrogels still exhibited shear thinning behavior with high recovery, which demonstrated that even though effective cross-links were formed, a complete network was not. Through this study, thiolnorbornene crosslinking of CNFs could create robust hydrogels and improve aqueous stability that could have applications in sustainable materials and biomaterials.more » « less
-
null (Ed.)Rice husks are an agricultural residue of great annual production and have a high cellulose content. In this study, we have prepared highly charged carboxyl cellulose nanofibers (CNFs) from rice husks using the TEMPO-oxidation method and the extracted CNFs were evaluated as an adsorbent for the removal of lead( ii ) and lanthanum( iii ) (Pb( ii ) and La( iii )) ions from contaminated water. Three different forms of nanocellulose adsorbents were prepared: suspension, freeze-dried, and nanocomposite containing magnetic nanoparticles, where their adsorption performance was tested against the removal of the two chosen heavy metal ions. The maximum adsorption capacity of rice husk based CNFs was found to be the highest in the nanocellulose suspension, i.e. , 193.2 mg g −1 for Pb( ii ) and 100.7 mg g −1 for La( iii ). The separation of the used adsorbent in the suspension was further facilitated by the gelation of the CNFs and metal cations, where the resulting floc could be removed by gravity-driven filtration. The absorption mechanism of the investigated CNF system is mainly due to electrostatic interactions between negatively charged carboxylate groups and multivalent metal ions. It was found that 90% lanthanum content in the form of lanthanum oxychloride (determined by X-ray powder diffraction) could be obtained by incinerating the CNF/LaCl 3 gel. This study demonstrates a viable and sustainable solution to upcycle agricultural residues into remediation nanomaterials for the removal and recovery of toxic heavy metal ions from contaminated water.more » « less
-
Anionic carboxylated cellulose nanofibers (CNF) are effective media to remove cationic contaminants from water. In this study, sustainable cationic CNF-based adsorbents capable of removing anionic contaminants were demonstrated using a simple approach. Specifically, the zero-waste nitro-oxidization process was used to produce carboxylated CNF (NOCNF), which was subsequently converted into a cationic scaffold by crosslinking with aluminum ions. The system, termed Al-CNF, is found to be effective for the removal of fluoride ions from water. Using the Langmuir isotherm model, the fluoride adsorption study indicates that Al-CNF has a maximum adsorption capacity of 43.3 mg/g, which is significantly higher than that of alumina-based adsorbents such as activated alumina (16.3 mg/g). The selectivity of fluoride adsorption in the presence of other anionic species (nitrate or sulfate) by Al-CNF at different pH values was also evaluated. The results indicate that Al-CNF can maintain a relatively high selectivity towards the adsorption of fluoride. Finally, the sequential applicability of using spent Al-CNF after the fluoride adsorption to further remove cationic contaminant such as Basic Red 2 dye was demonstrated. The low cost and relatively high adsorption capacity of Al-CNF make it suitable for practical applications in fluoride removal from water.
-
During the past decade, cellulose nanofibrils (CNFs) have shown tremendous potential as a building block to fabricate new advanced materials that are both biocompatible and biodegradable. The excellent mechanical properties of the individual CNF can be transferred to macroscale fibers through careful control in hydrodynamic alignment and assembly processes. The optimization of such processes relies on the understanding of nanofibril dynamics during the process, which in turn requires in situ characterization. Here, we use a shear-free mixing experiment combined with scanning small-angle X-ray scattering (scanning-SAXS) to provide time-resolved nanoscale kinetics during the in situ assembly of dispersed cellulose nanofibrils (CNFs) upon mixing with a sodium chloride solution. The addition of monovalent ions led to the transition to a volume-spanning arrested (gel) state. The transition of CNFs is associated with segmental aggregation of the particles, leading to a connected network and reduced Brownian motion, whereby an aligned structure can be preserved. Furthermore, we find that the extensional flow seems to enhance the formation of these segmental aggregates, which in turn provides a comprehensible explanation for the superior material properties obtained in shear-free processes used for spinning filaments from CNFs. This observation clearly highlights the need for different assembly strategies depending on morphology and interactions of the dispersed nanoparticles, where this work can be used as a guide for improved nanomaterial processes.more » « less