Preparation and characterization of nanocrystalline cellulose via low-intensity ultrasonic-assisted sulfuric acid hydrolysis
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Nanocrystalline cellulose (NCC) was extracted from microcrystalline cellulose via low-intensity ultrasonic-assisted sulfuric acid hydrolysis process. NCC samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size distribution (PSD) analysis, Fourier-transformed infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and rheological measurement. It was found that NCC yield reached 40.4 % under the optimum process of low-intensity ultrasonic-assisted sulfuric acid hydrolysis, while it was only 33.0 % in the absence of ultrasonic treatment. Furthermore, the results showed that the two NCC samples obtained from ultrasonic-assisted hydrolysis and conventional hydrolysis were very similar in morphology, both exhibiting rod-like structures with widths and lengths of 10–20 and 50–150 nm, respectively. XRD result revealed that the NCC sample from ultrasonic-assisted hydrolysis contained a small amount of cellulose II and possessed a Segal Crystallinity Index of 90.38 % and a crystallite size of 58.99 Å, higher than those of the NCC sample from conventional hydrolysis. Moreover, PSD analysis demonstrated that the former exhibited a smaller value in average particle size than the latter. In addition, rheological measurements showed that the NCC suspensions from the ultrasonic-assisted process exhibited a lower viscosity over the range of shear rate from 0.1 to 100 s−1 in comparison with that prepared in the absence of ultrasonic treatment.
KeywordsNanocrystalline cellulose Sulfuric acid hydrolysis Ultrasonic treatment Yield Microstructure
This work was financially supported by the National Natural Science Foundation of China (Grant No. 31100442), the Science and Technology Program of Hangzhou City of China (Grant No. 20120433B63), the Science and Technology Program of Zhejiang Environmental Protection Bureau of China (Grant No. 2012B008), Zhejiang Provincial Top Key Academic Discipline of Chemical Engineering and Technology and 521 Talent Cultivation Program of Zhejiang Sci-Tech University (Grant No. 11110132521310).
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