In this study, the effect of antisolvents on the structure of regenerated microcrystalline cellulose (MCC) obtained from the extraction of 1-butyl-3-methylimidazolium chloride (BmimCl) was investigated; further, the usage of the aqueous N,N-dimethylmethanamide (DMF) solution was proposed as an effective antisolvent for cellulose regeneration. The results denoted that regeneration after dissolution resulted in a looser cellulose texture with a high specific surface area, low degree of polymerization (DP), low crystallinity index (CrI), and decreased thermostability, which are favorable for its downstream processing. Among the studied antisolvents, the DMF solution was superior in cellulose regeneration from BmimCl, as demonstrated by the kinetics of enzymatic hydrolysis. The improved ability of the DMF solution with respect to cellulose regeneration can be attributed to the effective dispersion of H-bonds and the inductive hydrophobic orientation of cellulose chains; correspondingly, a looser H-bond network was observed in the regenerated cellulose. The DMF solution as an antisolvent offers an effective cellulose regeneration method and an optimal structure for subsequent processing and applications.
The ink-absorption capacity is an important factor for evaluating the printing quality of paper. In this study, the effects of different parameters of papermaking on the ink-absorption capacity of paper were investigated. The results showed that hardwood pulp exhibited better performance in increasing the absorptivity of paper compared with softwood pulp. When the content of hardwood pulp in paper was increased from 0% to 100%, the ink mark length decreased from 5.1 cm to 4.3 cm. Furthermore, a basis weight change from 100 g/m2 to 60 g/m2 increased the ink-absorption capacity, as revealed by a decrease of the ink mark length from 4.8 cm to 4.4 cm. Both sizing agent and beating degree affected the ink-absorption performance of the paper. For example, a shorter ink mark length of 5.1 cm was obtained at a low beating degree of 5000 r compared with that of 5.1 cm at 15000 r.
Crude enzyme secreted from Trametes sp. lg-9 was applied in biomechanical pulping of poplar. The Canadian Standard Freeness (CSF) of the pulp pretreated with crude enzyme by a charge of 8 IU g -1 pulp was 215 mL. However, the CSF of untreated pulp was 235 mL at the same refining revolutions of 15000. Also, the energy consumption during refining was significantly lowered. The brightness of enzyme-pretreated pulp was increased by 2%, and the light absorption coefficient and opacity were decreased slightly. The effect of H2O2 (P) and CH3COOOH-H2O2 (PaP) bleaching were reinforced, and the brightness of pulp was further enhanced when the dosage of crude enzyme was great than 8 IU g -1 pulp. However, the content of fines was decreased, and the lowest value was 6.99% when the dosage of crude enzyme was 8 IU g -1 pulp. The results of this work will be valuable for future possible commercialization.
Sulfonated cellulose (SC) with varying degrees of substitution (DS) were prepared with the pyridine sulfur trioxide complex (Py-SO3) as a sulfonation reagent (as a source of sulfur trioxide) in dimethyl formamide (DMF) as a solvent, where the DS was primarily affected by the molar ratio between Py-SO3 and the anhydroglucose (AHG) unit. Sulfonation temperature and residence time have less effect on DS. The ratio of the crystalline domain of SC decreased gradually with incremental DS, and the crystalline cellulose I of SC at DS0.81 nearly disappeared, and the moiety of the paracrystalline SC with high hydrophilicity increased. The thermostability decreased with increasing DS as a consequence of crystalline domain decrement. The adsorption performance of SC to metal ions was enhanced with increasing DS. However, above DS 0.62, the adsorption capacity enhancement is negligible. For an economic adsorption of heavy meatal ions in effluents, the DS of SC must be optimized.
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