Hydrochloric Acid Hydrolysis of Pulps from Oil Palm Empty Fruit Bunches to Produce Cellulose Nanocrystals
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Cellulose nanocrystals (CNCs) were successfully isolated by hydrochloric acid hydrolysis followed by ultrasonic homogenization of oil palm empty fruit bunches (OPEFB), which are a major form of agricultural waste in Southeast Asia. Currently sulfuric acid is mainly used in CNC preparation to achieve high dispersibility; however, we demonstrated that CNC suspensions prepared from OPEFB by hydrochloric acid hydrolysis remained stable without any sedimentation over 6 months. The obtained CNCs were fully characterized by elemental analysis, electron microscopic observation, X-ray diffraction measurement, and thermal analysis. The OPEFB-derived CNCs exhibited higher aspect ratios of 23–29 and higher thermal stability of 347–359 °C as maximum degradation temperature, as compared with those of woody CNCs prepared by sulfuric acid hydrolysis (15 and 311 °C, respectively). Although as-prepared CNCs showed comparable morphological and physicochemical properties to those prepared from oil palm biomass by other methods including sulfuric acid hydrolysis, use of hydrochloric acid and ultrasonication for hydrolysis of OPEFB was effective to yield crystalline CNCs with long-term nanodispersibility showing clear birefringence.
KeywordsCellulose nanocrystal Nanocellulose Hydrochloric acid Oil palm empty fruit bunch Agricultural waste
This research was supported by an Advanced Low Carbon Technology Research and Development Program from the Japan Science and Technology Agency (T.K.) and by a Research Fellowship for Young Scientists from Japan Society for the Promotion of Science (K.K.). The authors are grateful to Kurnia Wiji Prasetyo, M.Sc. from Biomaterial Research Institute, Indonesian Institute of Sciences, for kindly providing oil palm empty fruit bunches pulp for this research, and the Ministry of Education and Culture, Republic of Indonesia, for partial financial support through the Unggulan Scholarship (N.H.). The authors also thank Prof. Dr. Syuntaro Hiradate and Prof. Dr. Yuki Mori for performing XRD analysis.
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