Cellulose Nanofibers as Functional Biomaterial from Pineapple Stubbles via TEMPO Oxidation and Mechanical Process

Kenly Araya-Chavarría,Ruth Rojas,Marianelly Esquivel-Alfaro,Karla Ramírez-Amador,Belkis Sulbarán-Rangel,Orlando Rojas

doi:10.1007/s12649-021-01619-3

Abstract

The pineapple fruit when harvested generates a large amount of residual biomass; this biomass can be used to generate value-added products such as cellulose nanofibers. This study was focused on the isolation of CNF from pineapple leaves after oxidation pretreatment with 2,2,6,6-tetramethylpireridine-1-oxyl, followed by mechanical deconstruction of the fibers via combination of grinding and microfluidization process. One and two microfluidization passes were applied to bleached and unbleached fibers, respectively. The implications of these findings are that during the production process it is possible to reduce the amount of chemicals needed for bleaching and the energy involved in the mechanical microfluidization process. Such process yielded corresponding fibril lengths and widths in the range of 481–746 nm and 16–48 nm. The respective electrostatic charges, as measured by zeta potentials, were −41 mV and −31 mV. As expected, the CNF crystallinity was higher than that of the starting material, especially for the cellulose. However, the thermal stability was reduced, showing two degradative processes due to the chemical modification of the fibers. The CNF produced from pineapple leaves has a potential to be used like biomaterial in diverse applications while representing a viable alternative to producers, which face serious environmental and health challenges given the large volume of biomass that is otherwise left in the fields as waste.Graphic

Highlights

The novelty of this investigation was to produce bleached and unbleached cellulose nanofibers from pineapple leaves using an oxidative pretreatment with 2,2,6,6-tetramethylpiperidine1-oxy (TEMPO) followed by mechanical combination of grinding and microfluidization process
The characteristics of nanofibers was similar independent of the cellulose. The implications of these findings are that during the production process it is possible to reduce the amount of chemicals needed for bleaching and reduce the energy involved in the mechanical microfluidization process
During the isolation of cellulose nanofibers, the starting pineapple leaves fibers (PALF) must be exposed to different reactions that generate chemical composition changes

Summary

Introduction

The novelty of this investigation was to produce bleached and unbleached cellulose nanofibers from pineapple leaves using an oxidative pretreatment with 2,2,6,6-tetramethylpiperidine1-oxy (TEMPO) followed by mechanical combination of grinding and microfluidization process. The novelty was to take advantage of pineapple stubble waste and give it a beneficial use for the elaboration of advanced materials Through this process, it was found that the PALF is a suitable source for the extraction of nanofibers and the TEMPO pretreatment reduced the number of steps in the microfluidization process. The novelty of this research is producing CNF from pineapple leaves white cellulose bleached and unbleached using an oxidative pretreatment with TEMPO followed by mechanical combination of grinding and microfluidization process. The pretreatment of the fibers by TEMPO oxidation enhances the dispersibility in water, given the electrostatic repulsion generated by the formation of anionic carboxylate groups [28] This will help to reduce the steps through the microfluidizer and, the energy consumption of the mechanical processes will be reduced. The high electrical energy consumption typical of mechanical nanocellulose production is a significant drawback, from the point of view of both environmental impact and production cost [15]

Materials and Methods

Results and Discussion

Conclusions