Valorization of an agro-industrial waste, mango seed, by the extraction and characterization of its cellulose nanocrystals

Mango seeds are lignocellulosic agro-industrial residues available in large quantities in tropical countries and are simply discarded or used as animal feed. They are a natural and renewable resource, and were used to generate new polymeric materials in this work. This new materials can be used as alternatives to fossil resources such as petroleum. This work aimed to extract and characterize cellulose nanocrystals (CN) from mango seed by acid hydrolysis to obtain a material suitable as a reinforcing agent in the manufacturing of nanocomposites. The fibers of mango seeds were ground in mills and purified mainly to remove lignin. The raw mango seed (MS) and the purified mango seed (PMS) were analyzed for chemical composition and characterized by infrared and X-rays. Cellulose nanocrystals from the mango seed (CNM) were isolated by acid hydrolysis at 40 °C for 10 min, with 20 ml of H2SO4 (11.21 M) used for every gram of cellulose. The yield at this step was 22.8%. CNM were needle-shaped, with high crystallinity (90.6%), good thermal stability (around 248 °C), a medium length (L) of 123.4 ± 22.1 nm and a diameter (D) of 4.59 ± 2.22 nm, giving an aspect ratio (L/D) of about 34.1 ± 18.6. The diameter measurements of CNM were also confirmed by Scherrer's equation. This work also aimed to reuse mango seed produced as industrial waste, giving it a useful application and preventing its role as an environmental pollutant.

► Cellulose nanocrystals (CN) were extracted from mango seeds.
► CN presented high crystallinity and good thermal stability.
► CN obtained have great potential as reinforcement agents in nanocomposites.
► An added value of an agro-waste material through its reuse was demonstrated.