Assessing cellulose nanofiber production from olive tree pruning residue

Abstract

Pruning operation in olive trees generates a large amount of biomass that is normally burned causing severe environmental concern. Therefore, the transformation of this agricultural residue into value-added products is imperative but still remains as a technological challenge. In this study, olive tree pruning (OTP) residue is evaluated for the first time to produce cellulose nanofibers (CNF). The OTP bleached pulp was treated by TEMPO-mediated oxidation and subsequent defibrillation in a microfluidizer. The resulting CNF was characterized and compared to CNF obtained from a commercial bleached eucalyptus kraft pulp using the same chemi-mechanical procedure. CNF from OTP showed higher carboxylate content but lower fibrillation yield and optical transmittance as compared to eucalyptus CNF. Finally, the visco-elastic gel obtained from OTP was stronger than that produced from eucalyptus. Therefore, the properties of CNF from OTP made this nanomaterial suitable for several applications. CNF from OTP showed higher carboxylate content as compared to eucalyptus CNF (1038 vs. 778μmol/g) but lower fibrillation yield (48% vs. 96%) and optical transmittance. Finally, the visco-elastic gel obtained from OTP was stronger than that produced from eucalyptus. Therefore, the properties of CNF from OTP made this nanomaterial suitable for several applications.

Keywords: Agricultural residue; Cellulose nanofibers; Olive tree pruning; TEMPO-mediated oxidation.