Efficient separation of cellulose from Bamboo by organic alkali

Abstract

Abstract This study focuses on the effective separation of cellulose from bamboo through a two-step process. Several organic alkalies 2-pyrrolidinone, ethylurea, dibutylamine, N-methylformamide and tetramethyl guanidine were used to remove lignin and isolate cellulose from massive bamboo. The results showed that tetramethyl guanidine can effectively remove lignin and hemicellulose while retaining almost all the cellulose in the residual solid. The removal of lignin and hemicellulose achieved 86.0% and 84.0% after heating for 3h at 150°C, respectively. Subsequently, the final remove of lignin and hemicellulose increased to 91.5% and 93.8%, respectively, after a simple alkaline H2O2 bleach treatment. Interestingly, the loss of cellulose was very small after two-step treatments, and 96.9% of the component was still retained. The crystalline increased from 61.3–68.4% in XRD graphs due to the remove of lignin and hemicellulose. The SEM images indicated that the diameter of cellulose bundles decreased from 80–100µm to about 50µm after organic alkali treatment, and then the fiber bundle was completely separated into a single long fiber with a diameter of about 10 µm after H2O2 bleaching. The FT-IR spectra confirmed the high selective removal of lignin and hemicellulose. Two-dimensional 1H-13C NMR (2D HSQC) spectra were analyzed to investigate the lignin structure, and found that only the signals of –OCH3, Cγ-Hγ in β-O-4' (Aγ) and β-β' (Cγ) structures and C5-H5 in guaiacyl (G5) did not disappear after two-step treatment.