Isolation of cellulose nanofibers from poplar wood and wheat straw: optimization of bleaching step parameters in a chemo-mechanical process by experimental design

Abstract

Isolation of cellulose nanofibers was carried out from two diverse cellulosic sources, wood (poplar) and non-wood (wheat straw), by means of a developed chemo-mechanical treatment with emphasis on optimizing the bleaching step. During chemical treatments, the effect of the primary bleaching step on the quality of cellulose microfibers was investigated at different times and temperatures. Furthermore, to optimize bleaching conditions, Klason lignin was calculated, and the effect of bleaching steps on the Klason lignin was also studied. National renewable energy laboratory (NREL) procedure, Kappa number determination, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy were conducted for chemical and morphological characterization of cellulose fibers during experiments, and transmission electron microscopy and amount of energy consumption were used to analyze cellulose nanofibers. The results obtained from NREL, Kappa number, and FTIR indicated that noncellulosic compounds were dramatically removed during chemical treatments, and the average diameters of cellulose nanofibers were obtained to be 43 and 45.2 nm for wheat straw and poplar wood. Finally, it was found that during mechanical treatment, the amount of energy consumed by poplar wood was higher than wheat straw.