Microcrystals and Microfibers of Cellulose from Mangífera indica L. for Paper Industry Applications

Lignocellulosic residues are abundant and easily accessible. This work has evaluated the potential of the residues, shell (C), pulp (P), and seeds (S) of mango fruit as sources of cellulose for the preparation of microcrystals (MCC) and microfibers of cellulose (MFC), which could be used as additives in the paper industry. First, compositions of C, P, and S were determined, being the cellulose content 5.35%, 43.2%, and 52.45%, respectively. Then, the purification of the residues with high cellulose content (P and S) was carried out by alkaline treatment and bleaching. Next, to obtain MCC and MFC from P and S, a unifactorial design was used to study the relationship between the acid hydrolysis time (15, 30, and 60 min) and the crystallinity of the MCC, and the relationship between the mechanical treatment time (5, 10, and 20 min) and the diameter of the MFC. For the MCC, an increase in the crystallinity index at longer treatment times was observed, resulting in the best condition for both S and P, 60 min. For the MFC, a decrease in the diameter was verified in both S and P, as the treatment time increased, resulting in the best condition at 20 min. Different analytical methods were used during the processes of obtaining MCC and MFC, such as scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential thermogravimetric analysis (DTG). The obtained results such as high fibrillation of MFC and high crystallinity indexes CrI of MCC reveal the potential of the extracted cellulosic materials for applications in the paper industry since they should improve the mechanical properties of paper.