Isolation of Cellulose Nanocrystals from Banana Peel Using One-Pot Microwave and Mild Oxidative Hydrolysis System.

The current investigation deals with the application of a one-pot system to facilitate the production of cellulose nanocrystals (CNCs) from banana peel by a combination of microwave pre-treatment and mild oxidative hydrolysis with hydrogen peroxide (H 2 O 2 , 0-30 wt%) and sulfuric acid (H 2 SO 4 , 0-10%). H 2 O 2 causes decolorization of the banana peel suspension from dark brown to light yellow, while further treatment with H 2 SO 4 produces a white suspension, indicating successful removal of the non-cellulosic components from the banana peel. This finding was further supported by Fourier Transform Infrared (FTIR) spectroscopic analysis, which showed the gradual disappearance of lignin and hemicellulose peaks with increasing H 2 O 2 and H 2 SO 4 concentrations. The CNCs has considerably high crystallinity, with the highest crystallinity (~85%) being obtained at 6% H 2 SO 4 . Therefore, CNCs obtained at 6% H 2 SO 4 were selected for further characterization. Scanning Electron Microscope (SEM) analysis confirmed the disintegration of the cellulose fibres into small fragments after hydrolysis. Transmission Electron Microscope (TEM) and Atomic Force Microscope (AFM) analyses revealed the spherical shape of the CNCs with an average size of approximately 20 nm. The CNCs have good stability with zeta potential of -42.9 mV. Findings from this study suggest that the combination of microwave pre-treatment and oxidative hydrolysis with 30 wt% H 2 O 2 and 6% H 2 SO 4 , which is about 11 times lower than the commonly used H 2 SO 4 concentration, is proven effective for the isolation of CNCs from banana peel. These observations are expected to provide insight into a facile and environmentally benign alternative to the conventional CNCs isolation method, using abundant and underutilized agricultural waste as feedstock.