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Applications of cellulose nanocrystals (CNCs) in various fields of high value have been and are being widely studied. However, research about the fundamental preparation method has come to a standstill. This work aims to introduce a concept of progressive dissolution of cellulosic fibers and an eco-friendly way of preparing CNCs. By controlling TBAH concentration, the amphiphilicity and dissolving capability of TBAH/H2O can be regulated. Through a controlled partial dissolution of cellulose in the solvent, aqueous tetra-butylammonium hydroxide (TBAH), the fiber can be dissolved to make nanoscale particles (CNC suspensions). Polarized light microscopy provides a quantitative evaluation of the progress of dissolution, by which a processing window (43% TBAH/H2O, 30 min dissolution at room temperature) for preparing CNCs from cotton pulp has been determined. The multiscale cellulose products, including micron-scale, nanoscale, and well-dissolved products of cellulose, have been separated with the assistance of the derivatization process. There are interestingly homogeneous materials of cellulose I with a needle-like shape in the nanoscale products extracted. Furthermore, the cellulose raw materials can be extended from cotton pulp to wood pulp, bamboo pulp, straw pulp, and microcrystalline cellulose, indicating it to be a universal method. Analysis of XRD patterns of the raw and CNCs indicates that amorphous and less-crystalline cellulose can be precisely and controllably dissolved by the solvent, leaving CNCs. [ABSTRACT FROM AUTHOR]

TBAH(tetra-butylammonium hydroxide)/Urea/H2O solvent has been applied for the solvent wet-spinning of cellulose, due to its room temperature operation, good stability and spinnability of the cellulose solution, as well as the unconditional string of low DP (degree of polymerization) for dissolving cellulose. Most importantly, it is found that the stability of the cellulose solution can be dramatically improved by the addition of urea, as indicated by the rheological property of the cellulose solution. With the help of urea, it has been preliminarily studied about the effect of the drawing process, including tnf (time for the formation of nascent fiber in coagulation bath), δ1 (primary drawing ratio) and δ2 (secondary drawing ratio), on the orientation structure and the mechanical performances of the spun fibers. The correlations between the drawing process and the mechanical performance have been established by mathematical models. The tensile strength of the spun fibers improved up to ca. 96% (1.3 cN/dtex) through our optimization of the drawing process. Morphological observations indicated that the spun fibers exhibited regular shape with a circular cross-section. X-ray diffraction and scattering analysis demonstrated that the orientation structure of fibers spun by TBAH/Urea/H2O is similar to that of the commercial viscose and Tencel fibers. [ABSTRACT FROM AUTHOR]

A novel biosorbent PEI-HOCM was successfully prepared by grafting polyethyleneimine (PEI) onto H2O2-oxidized cellulose membrane (HOCM). The whole systhesis process occurred in aqueous solution and was environmentally friendly without any toxic cross-linkers involved. ATR-FTIR, XPS and titration analysis confirmed that the hydroxyl groups of cellulose were oxidized to carbonyl groups by H2O2 and PEI was successfully introduced to the HOCM. The PEI-HOCM had positively charged surface (+ 20.6 to + 86.6 mV) at the measured pH range 3–9 according to the zeta potential analysis. The adsorption of Cr(VI) on the PEI-HOCM obeyed the pseudo-second-order kinetic model and Langmuir isotherm model. Its maximum equilibrium adsorption capacity was 147.06 mg/g at 25 °C, which was much higher than that of cellulose membrane (CM, 30.61 mg/g). According to the obtained results from the intraparticle diffusion, Body kinetic and diffusion-chemisorption models, film diffusion was the rate-limiting step and chemical adsorption was the main mechanism of Cr(VI) adsorption. The Cr(VI) adsorbed on the PEI-HOCM was completely reduced to Cr(III), suggesting that PEI-HOCM was not only useful for Cr(VI) removal but also good for its detoxification. The competitive uptakes from coexisting components (Na+, Mg2+, Ca2+, phenol, Cl− and NO3−) were insignificant except H2PO4− and SO42− which reduced the Cr(VI) uptake with a efficiency loss of 22–41%. Ionic strength had little effect on the adsorption in the range of 0–1000 mg/L NaCl. After five adsorption/desorption cycles, the PEI-HOCM still retained good adsorption capacity. More importantly, it can be separated easily after adsorption, which will greatly benefit the wastewater treatment by simplifying the separation procedure and reducing costs. [ABSTRACT FROM AUTHOR]