Cellulose microfibrils from banana rachis: Effect of alkaline treatments on structural and morphological features

Four different alkaline treatments for isolation of cellulose microfibrils from vascular bundles of banana rachis were comparatively studied. Isolated cellulose microfibrils were characterized using high performance anion exchange chromatography for neutral sugar composition, as well as attenuated total reflection Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray and electron diffraction and solid-state ¹³C NMR. The cellulose microfibrils treated with peroxide alkaline, peroxide alkaline–hydrochloric acid or 5 wt% potassium hydroxide had average diameters of 3–5 nm, estimated lengths of several micrometers. Although the interpretation of their structure is difficult because of the low cristallinity, X-ray diffraction, ¹³C NMR and ATR-FTIR results suggested that cellulose microfibrils from banana rachis could be either interpreted as cellulose IV₁ or cellulose Iβ. The specimens treated with a more concentrated KOH solution (18 wt%) were still microfibrillated but their structure was converted to cellulose II.