Chemical modification is a reliable and efficient strategy for designing cellulose-based functional materials. Herein, porous quaternized cellulose beads (QCBs) as cationic superabsorbent were ...fabricated by homogeneous in-situ chemical grafting cellulose molecular chains with glycidyl trimethylammonium chloride (GTAC) in tetraethylammonium hydroxide (TEAOH)/urea aqueous solution followed by acetic acid induced regeneration. The influence of GTAC dosage on the physicochemical-structural properties of cationic QCBs was deeply investigated. Results revealed that cotton liner could well-dissolved in TEAOH/urea aqueous solution, leading to a homogeneous and efficient quaternization medium for cellulose, thereby giving the high DS and positive charge density for quaternized cellulose. NMR results demonstrated the main substitution of GTAC groups at 2-OH and 6-OH positions of the cellulose chains during quaternization reaction. With increasing GTAC dosage, the network skeleton of QCBs gradually transformed from thick fibrils to thin aggregates, as well as enhanced pore volumes and hydrophilicity. Accordingly, QCBs-1.5 with high pore volume (99.70 cm3/g) exhibited excellent absorption capacity and efficiency, absorbing 122.32 g of water and 0.45 g of moisture per gram of the beads in 20 min. This work not only offers a simple strategy for the homogeneous quaternization modification of cellulose, but also provides a porous cellulose-based cationic superabsorbent material.
Display omitted
Cellulose-based materials, such as cellulose microspheres, have attracted enormous attention because of their widespread applications in water and protein purifications, chromatographic stationary ...phase, biocatalyst, drug delivery, electrode materials, etc. Here, homogenous and spherical porous regenerated cellulose microstructures (RCMSs) obtained from the agglomeration of micro/nanospheres were fabricated via a simple emulsion–coagulation–oven-drying process in pulp cellulose–tetraethylammonium hydroxide (TEAOH)/urea/H
2
O solution, and the formation mechanism of the RCMSs was investigated by controlling the synthesis time. The results revealed that the uniform micro/nanospheres with a narrow size distribution of 600 nm–6 μm were first synthesized, followed by the formation of the RCMSs via the continuous agglomeration of the micro/nanospheres with the increasing synthesis time. Additionally, the RCMSs exhibiting micro/nanoscale pores with an adjustable mean diameter (
r
) of 280–103 μm were readily prepared by controlling the stirring speed between 300 and 1200 rpm. The re-wetted RCMSs exhibited a swelling ratio (
SR
) of 690–1400%, indicating their excellent swelling performance. Furthermore, the RCMSs with the structure of cellulose II exhibited good physical properties, including high porosity (
P
r
, 90–93%), pore volume (
V
p
, 7.0–10.3 cm
3
/g), specific surface area (
S
, 40–70 m
2
/g), and chemical/thermal stabilities. These findings can contribute to the design and exploitation of highly functional cellulose-based materials exhibiting micro/nanostructures.
Porous regenerated cellulose microspheres (RCMs) have attracted increasing attention due to their wide range of applications from medical carriers to environmental remediation. Here, porous RCMs were ...synthesized for adsorption of cationic methylene blue dye using a simple emulsification–acid coagulation–oven-drying technique after dissolving pulp cellulose with a degree of polymerization (DP) of approximately 1500 in tetraethylammonium hydroxide (TEAOH)/urea solvents at room temperature. The RCMs with controllable size (20 to 224 µm) and high pore volume (8.24 to 10.20 mL/g) were prepared by varying the dosage of the surfactant polyoxyethylene sorbitan monooleate (polysorbate 80). Moreover, the viscosity of the cellulose solution steadily decreased with storage time due to the decrease in cellulose DP, but the effect on the particle size and morphology of RCMs was negligible, which could be advantageous to the scalable production of RCMs. When used as an adsorbent for cationic methylene blue dye removal, it showed high adsorption efficiency (1 h to achieve equilibrium, 24.5 mg/g), stability, recyclability, and reusability.
•Composite filler by using cellulose nanofibrils, PCC and C-starch was developed.•Paper loaded with composite fillers had higher strength properties than PCC loading.•Paper loaded with composite ...fillers became denser with increasing the filler content.
A new concept of composite filler was developed by using cellulose nanofibrils (CNF), precipitated calcium carbonate (PCC) and cationic starch (C-starch). In this study, cellulose nanofibrils were utilized in two different ways: a PCC–CNF composite filler and a papermaking additive in sheet forming. The aim was to elucidate their effects on flocculation, filler retention and the strength and optical properties of handsheets. The highest filler retention was obtained by using the PCC–CNF composite filler in paper sheets. The paper filled with the composite fillers had much higher bursting and tensile strengths than conventional PCC loading. It was also found that the paper prepared with PCC–CNF composite fillers became denser with increasing the filler content of paper.
Display omitted
Cellulose aerogel beads (CABs) have emerged as advanced biomaterials with numerous engineering applications, including chromatography and drug release. In this study, porous ...core–shell CABs were synthesized using a dilute ethanol solution-substitution-assisted freeze-drying. The formation mechanism of the CABs and the effect of ethanol concentration on the core–shell microstructures and physical properties were investigated. Cellulose hydrogel beads (CHBs) were formed through the exchange/neutralization of acetic acid with tetraethylammonium hydroxide (TEAOH)/urea. The cellulose chains dissolved in the cellulose–TEAOH/urea droplets regenerated from the edge to the inside of the droplet in an acetic acid bath. Notably, adding ethanol at a concentration of 10% before freeze-drying can result in core–shell CABs with non-obvious structural shrinkage, large particle size, uniform pores, and high porosity. Ethanol molecules induce ice crystal growth to form more uniform ice crystals during the freezing process. Additionally, by altering the TEAOH/urea molar ratios and cellulose concentrations of cellulose solutions, well-shaped and porous CABs were prepared, demonstrating the feasibility and availability of dilute ethanol solution-assisted freeze-drying. Consequently, the as-fabricated CABs had a dense micro-shell (1–9 μm) and loose millimetric-core with anisotropic pores (2–6 μm), exhibiting low density (0.06–0.09 g/cm3), high porosity (87.0–91.5%), and noteworthy thermal stability.
The objectives of this work were to investigate the effect of the degree of fibrillation and addition method of cellulose nanofibrils (CNFs) into the wet end of the papermaking process on the ...drainage, filler retention, strength and optical properties of handsheets. CNFs were produced with the grinding method, and the degree of fibrillation was manipulated by varying the passing number through the grinder from 15 to 50 passes. The CNFs were added to the wet end of the papermaking process in two different ways: a precipitated calcium carbonate (PCC)-CNF composite filler and a wet-end additive. The results showed that the water retention capacity of CNFs increased as the fibrillation was performed, and this resulted in an increase in drainage time. The solid content of handsheets filled with composite filler was about 1–2% higher than in the CNF-added sheets after wet pressing. Furthermore, the composite filler-filled sheets with higher ash content had similar tensile strength, compared with the CNF-added sheets. It was also found that water retention capacity of CNFs increased as the fibrillation was performed, and this resulted in an increment in drainage time and a reduction in solid content of sheets after wet pressing. The more fibrillated CNFs significantly (
p
<
0.05) increased the density and tensile strength of sheets, which might be due to the increased number of inter-fiber bonds. Filler retention and opacity were not significantly influenced by the fibrillation degree of CNFs.
Three alkali swelling methods were used to treat two kinds of kraft pulp fibers. The morphological and chemical properties of the treated fibers were elucidated in terms of alkali concentration, with ...the aim of developing bulky paper and conserving wood resources. The effects of beating before and after alkali swelling were examined. The water retention value of fibers increased when higher concentrations of NaOH were used for swelling. Alkali swelling increased fiber width, while fiber length decreased. With increasing NaOH concentration, fibers became curled or kinked; the crystalline structure changed from cellulose I to cellulose II, and the crystalline index decreased. Beating before and after the alkali swelling affected the swelling behavior of kraft pulps, but there was no distinct influence on the crystalline structure. The beating treatment before alkali swelling improved the alkali swelling of fiber. However, beating after the alkali treatment diminished the alkali swelling effects. In addition, the beating after alkali swelling straightened the curled fibers.
A composite filler was developed by pre-flocculation of fiber fines and precipitated calcium carbonate (PCC) particles with flocculants such as cationic polyacrylamide (cPAM) and bentonite. The ...composite filler was compared with a conventional loading method in terms of physical properties of handsheet and filler retention. The handsheets using the composite filler showed higher strength properties than that using a conventional loading at a similar paper ash content level, implying that paper ash content can be increased maintaining same level of paper strength. Optical properties such as opacity and brightness of the paper with the composite were quite similar with the paper with the conventional loading. Filler retention of the composite filler was slightly higher than that of the conventional loading even though retention aids were not used for the composite filler. Paper formation of the composite filler was better than the case of the conventional loading. However, the sheet with the composite filler showed lower bulk than that with the conventional loading. Conclusively, the composite filler technology by pre-flocculation of fines and filler has a potential to be utilized to produce a high loaded paper.
Effects of alkali swelling of kraft pulp fibers and the order of alkali swelling and beating treatments on paper bulk and paper strength were evaluated in terms of NaOH concentration in order to ...produce high bulk sheet (i. e., high porous and low density sheet). Effects of replacement of part of furnish with the alkali swollen pulp on paper properties were also investigated. It was found that alkali swelling of pulp fiber can increase the bulk of handsheet. NaOH concentration and beating treatment influenced paper bulk and paper strength. Alkali swollen pulp without beating showed the highest handsheet bulk. The paper bulk of alkali swollen pulp with pre-beating was higher than that with post-beating. Paper strength decreased with increasing the bulk of handsheet. In addition, replacement of part of furnish with alkali swollen pulps increased paper bulk, adversely decreasing paper strength. The highest improvement in paper bulk was achieved with the addition of alkali swollen SwBKP without beating.
Spent cooking liquor from kraft pulping, known as black liquor, was applied to linerboard (corrugated medium) by surface sizing in order to increase strength properties. The influence of alum in ...black liquor on linerboard properties was also investigated. The surface application of black liquor improved the dry strength of linerboard. A slight addition of alum into black liquor (2.5% on black liquor solids) significantly improved strength properties such as tensile strength, TEA, compressive strength, and bursting strength. The results implied that black liquor with alum can be used for industrial grade papers that require high strength properties. The air permeability of corrugated medium increased after 5 g/m2 of dry pick-up. Black liquor appeared to penetrate the paper pores, and aggregates of lignin and carbohydrates in the black liquor increased bonds between fibers, which improved strength. The surface sizing of black liquor and alum addition also affected the hydrophobicity of linerboard.
PDF
