Preparation and Characterization of Porous Cellulose Acetate Nanofiber Hydrogels.

The currently reported methods for preparing cellulose acetate hydrogels use chemical reagents as cross-linking agents, and the prepared ones are non-porous structured cellulose acetate hydrogels. Nonporous cellulose acetate hydrogels limit the range of applications, such as limiting cell attachment and nutrient delivery in tissue engineering. This research creatively proposed a facile method to prepare cellulose acetate hydrogels with porous structures. Water was added to the cellulose acetate-acetone solution as an anti-solvent to induce the phase separation of the cellulose acetate-acetone solution to obtain a physical gel with a network structure, where the cellulose acetate molecules undergo re-arrangement during the replacement of acetone by water to obtain hydrogels. The SEM and BET test results showed that the hydrogels are relatively porous. The maximum pore size of the cellulose acetate hydrogel is 380 nm, and the specific surface area reaches 62 m2/g. The porosity of the hydrogel is significantly higher than that of the cellulose acetate hydrogel reported in the previous literature. The XRD results show that the nanofibrous morphology of cellulose acetate hydrogels is caused by the deacetylation reaction of cellulose acetate.

Simultaneous microwave-assisted phosphotungstic acid catalysis for rapid improvements on the accessibility and reactivity of Kraft-based dissolving pulp.

Improving the cellulose accessibility and reactivity in an efficient and convenient way has become the focused issue in the field of dissolving pulp manufacturing. We herein demonstrate a simple yet efficient strategy, namely a simultaneous microwave (MW)-assisted phosphotungstic acid (PTA) catalysis (MW-PTAsim). The MW-PTAsim treatment was efficient to improve Fock reactivity from 49.1 % to 85.8 % and decrease viscosity from 561 to 360 mL/g within 10 min, which was superior to the single MW treatment and the sequential MW-PTAseq treatment. Besides, the MW-PTAsim treated fiber had rougher and more fibrillated surfaces with an enhanced fiber accessibility, showing increased specific surface area (SSA) from 1.43 to 6.31 m2/g, mean pore diameter (MPD) from 6.92 to 11.20 nm and water retention value (WRV) from 101 % to 172 %. These positive enhancements are mainly due to a synergy that MW-enhanced rotation of PTA mediums was served as "spinning cutters" to attack the fibers, plus MW-accelerated PTA transfer and catalytic hydrolysis further improved the fiber accessibility. Moreover, PTA also demonstrates a high reusability and chemical stability. This process offers an effective and sustainable alternative for manufacturing a premium dissolving pulp.

Ultrafast process of microwave-assisted deep eutectic solvent to improve properties of bamboo dissolving pulp.

Viscosity control and reactivity enhancement are critical to produce high-quality cellulose products, such as dissolving pulp, yet remain challenging. In this work, an ultrafast process, namely microwave-assisted deep eutectic solvent (MW-DES), is proposed for this purpose. It is based on the hypothesis that the MW-DES process can deliver an enhanced synergy: a simultaneous fiber swelling and cellulose depolymerization via hydrogen-bonding break-up and acid hydrolysis from the actions of polar and acidic DES further boosted under MW irradiation. Results showed that after the MW-DES (Choline chloride- oxalic acid, ChCl-OA) treatment for only 40 s, the pulp viscosity decreased from 715 to 453 mL/g, and the reactivity increased from 43.0 % to 84.6 %, which is ultrafast in comparison with those reported work. Furthermore, DES in the process shows a high reusability and chemical stability, thus offering a simple, sustainable and effective alternative for upgrading of dissolving pulp, particularly, using non-wood materials of bamboo.

Solvent-free preparation of thermoplastic bio-materials from microcrystalline cellulose (MCC) through reactive extrusion.

Cellulose, as a renewable biopolymer, was acknowledged as a promising alternative for petroleum polymer. However, the poor thermoplasticity of cellulose caused a limitation in its full development. Herein, a solvent-free and simple strategy was proposed for the preparation of thermoplastic bio-materials from microcrystalline cellulose (MCC). Kraft lignin (KL) was employed as a plasticizer in this work. It was demonstrated that MCC-based materials with great thermoplasticity and mechanical properties could be successfully prepared by reactive extrusion. The obtained MCC-based material ML8G (with 50 wt% KL adding) possessed great thermostability and thermoplastic properties with an obvious glass transition temperature (Tg) at 106 °C. In addition, the bending strength, flexural modulus and storage modulus of the MCC-based material were improved to 20.44 MPa, 3139.47 MPa and 5.81 GPa respectively. Furthermore, the obtained MCC-based material exhibited good water stability and biodegradability. The comprehensive results confirmed the feasibility of MCC-based materials plasticized with KL through reactive extrusion. Overall, this work was a promising development in the field of bio-plastic utilization of natural products from a green source.

Insights into structure and properties of cellulose nanofibrils (CNFs) prepared by screw extrusion and deep eutectic solvent permeation.

To achieve the balance on economy and ecology, it is indispensable to explore the greener and more inexpensive method for the production of cellulose nanofibrils (CNFs). Herein, a deep eutectic solvent (DES) system based on choline chloride (ChCl) and ethylene glycol (EG) was employed as the swollen solvent, combining with screw extrusion and permeant, to fabricate unmodified CNFs with high yield and thermal stability. The proposed method in this work was simple, convenient, and industrially viable. The hydrous DESs were applied in the process of CNFs preparation and dispersion to reduce the cost and viscosity of DES. To reveal the principle of CNFs preparation, the impact of sulfuric acid and water content of DES system on the chemical, physical, morphological, thermal, and dispersive properties of CNFs was systematically studied. Properties of the dispersed solvents were characterized by solvatochromic parameters and viscosity parameters to evaluate the potential influence on the preparation and dispersion of CNFs. In general, this work would play valuable guidance in realizing the preparation and dispersion of CNFs via a versatile DES solvent system, thus endowing cellulose materials high-value utilization.

Experimental study on the relationship between the mineral production capability and the physiochemical properties in the coproduction of Q phase-3CaO·3Al2O3·CaSO4 cement clinker.

A coproduction tests of quaternary (Q) phase(6CaO·4Al2O3·MgO·SiO2) -3CaO·3Al2O3·CaSO4 cement clinker and an experimental study on the relationship between the mineral production capability and the physiochemical properties are conducted in a two-stage multiphase reaction test bed with Changguang coal. X-ray diffractometer (XRD) analyses are performed on the coproduction clinker samples. The results demonstrate that, with the reduction in particle sizes of the coal powder and the additives and expanded screening level differences between them, both the proportion of Q phase and the mass of 3CaO·3Al2O3·CaSO4 in the clinker increase accordingly. When mixed coal powder particles are prepared through reducing particle sizes and expanding screening level differences between coal powder and additives, the additives CaO and MgO are more likely to be enclosed by coal powder to form globular polymerized particles. In addition, this preparation aids in polymerization and promotes even distribution of CaO, MgO and coal minerals, thus facilitating clinker mineral formation reactions of inorganic substances in the mixed coal powder. Target minerals, such as 2CaO·SiO2 and Q phase, are found in both industrial high-calcium limestone and low-calcium limestone coproduction clinker samples. A diffraction peak of free CaO is also evident in both samples. Compared with a coproduction clinker sample of high-calcium limestone, that of low-calcium limestone exhibits higher diffraction peaks for 2CaO·SiO2 and Q phase. With the current state of the art, it is not yet the optimum choice to substitute CaCO3 for CaO in Q-phase cement clinker coproduction. Before the technology matures and gains practical application, further study on the form and the mixing process of calcium-based additives for cement clinker coproduction will be required.