Purpose: A variety of lignocellulosic raw materials have been previously reported for the production of cellulose and cellulose derivatives, but little research effort has been dedicated to producing cellulose from Hyparrhenia filipendula . In this study, cellulose nanofibers (CNFs) were extracted from Hyparrhenia filipendula waste straws via sulphuric acid hydrolysis.
Methods: The straws were pretreated with a combination of physiochemical processes and hydrolyzed using sulphuric acid at three different concentrations (1 M, 3 M and 5.6 M) for 2 hours at 80 °C. The properties of the CNFs was checked by Fourier Transform Infrared spectroscopy (FTIR) for surface chemistry, X-ray diffraction (XRD) for crystallinity, Scanning Electron microscopy and Transmission electron microscopy (TEM) for morphology. A high-performance liquid chromatograph (HPLC) was used to quantify the amount of biopolymers in the CNFs.
Results: The results show that CNFs, denoted as CNF 1 , CNF 3 , and CNF 5.6 for 1 M, 3 M, and 5.6 M sulphuric acid, respectively, were successfully extracted at the various concentrations of sulphuric acid. The cellulose content of CNF1 , CNF3 , and CNF5.6 determined by HPLC analysis were 85%, 77 % and 78 % respectively. Also, the hemicellulose content in CNF 1 , CNF 3 , and CNF 5.6 was 10 %, 15 %, and 12 % respectively, showing a high carbohydrate content of the CNFs. The FTIR spectra confirm the absence of characteristic peaks for lignin in the CNFs. The XRD analysis reveals presence of characteristic cellulose I β peaks at 2θ of 18°, 26°, and 40° with the crystallinity of 78%, 74 % and 73% for CNF1, CNF3 and CNF5.6, respectively. Moreover, SEM analysis shows the deposition of lignin polycondensate on the surface of CNF 1 , CNF 3 , and CNF 5.6 while the bleached sample has a smooth and glossy appearance. The TEM analysis shows long unbranched nano-sized fibers for CNF 1 and shorter fibrous network of fibers for CNF 3 , and CNF 5.6. The average diameter of the fibers, measured with ImageJ software is 40 nm for CNF 1 , 57 nm for CNF 3 , and 92 nm for CNF 5.6.
Conclusion: CNFs were successfully produced from Hyparrhenia filipendula and reported for the first time in open literature. In view of the structure and properties of the produced CNFs, they are a potential material for value-added applications such as polymer matrices, films, and membranes, thus enabling efficient utilization of agricultural waste.