Journal
CELLULOSE
Volume 27, Issue 9, Pages 5017-5028Publisher
SPRINGER
DOI: 10.1007/s10570-020-03113-w
Keywords
Cellulose nanofibers; Composite film; Poly(vinyl alcohol); Spent coffee grounds; TEMPO-mediated oxidation; Waste revalorization
Funding
- YNU Diversity Research Grant'' under MEXT Funds for the Development of Human Resources in Science and Technology, Initiative for Realizing Diversity in the Research Environment (Collaboration Type)''
- Yokohama National University
- Japan Society for the Promotion of Science (JSPS) KAKENHI [JP18H02387]
- Yokohama Academic Foundation [674]
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The waste valorization of spent coffee grounds (SCGs), which are obtainable in large amounts worldwide for new non-wood source has been considered. Cellulose nanofibers derived from SCGs have been successfully produced by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of SCGs containing 10% cellulose (dry weight). The TEMPO-oxidized cellulose nanofibers (TOCNFs) are 20-35 nm wide observed by scanning electron microscopy. X-ray diffraction showed that TOCNFs are present in a cellulose crystal form I. The average crystal size corresponding to a fiber width was 4.2 nm, as determined from the diffraction pattern. Solid-state NMR shows that hemicellulose and lignin were mostly removed from SCGs via TEMPO-mediated oxidation, but small amounts of triacylglycerols remained in the TOCNFs. Thermogravimetric analysis of TOCNFs showed two major steps of thermal decomposition at 251 degrees C and 267 degrees C, which were higher than the coffee roasting temperature range. Furthermore, in order to investigate an interaction of these TOCNFs with a polymer, a SCG-derived TOCNF composite film with poly(vinyl alcohol) as a water-soluble polymer was prepared. We found the TOCNFs were successfully integrated into the polymer. The outcome of this study indicated that SCGs could be used as well as wood as an alternative source for producing TOCNFs, thus contributing to the development of sustainable green chemistry. [GRAPHICS]
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