Extraction optimization and molecular dynamic simulation of cellulose nanocrystals obtained from bean forage

Abstract

The structural, energetic, and mechanical characteristics of cellulose were evaluated through molecular dynamic simulation on atomic scale in view of different applications. This research standardized the processing variables for the extraction of cellulose nanocrystals obtained from bean forage; the optimal conditions for the alkaline and bleaching treatments were: NaOH 1.75% w/w for 8.5 h with a bleaching time of 1 h at 70 °C with a yield of 25.51%; for the acid treatment the optimal conditions obtained were: H2SO4 at 55% for 30 min at 40 °C; in this case, the optimization was carried out with two responses: yield (60.68%) and crystallinity index (49.36%). The raw material was chemically characterized showing a cellulose content of 45.78 ± 0.888% wt. cellulose, 10.73 ± 0.732% wt. hemicellulose, 5.09 ± 0.753% wt. lignin, and other components. X-ray diffraction indicated changes in the diffraction patterns corresponding to the crystalline and amorphous areas of the cellulose. The percentages of crystallinity obtained with the optimal conditions were: 40.39% after the alkaline treatment, 42.02% after the bleaching treatment, and 49.36% after the acid treatment. Finally, the structure and molecular dynamics of cellulose nanocrystals obtained from bean forage created with Materials Studio 8.0 program were evaluated, in which geometric optimization was carried out applying the Quasi-Newton BFGS method. X-ray diffractograms generated by the program were compared against those obtained experimentally, validating the virtual structure of the nanocrystals by obtaining a similarity of 86%, which would allow exploratory research using molecular dynamics to find possible applications.