A STUDY ON THE EFFECTS OF ACID CONCENTRATION ON THE PROPERTIES OF NANOCELLULOSE EXTRACTED FROM SUNN HEMP (CROTALARIA JUNCEA) BY ACID HYDROLYSIS

Abstract

Nanocelluloses from sunn hemp (crotalaria juncea) was extracted by employing the process of acid hydrolysis. The present work focuses on two important objectives, firstly to valorise the sunn hemp fibers in the field of nanocellulose and second is to study the effects of acid concentration on the properties of nanocellulose (NC). The study was performed the extraction of nanocellulose at five different concentrations of H2SO4; 16%, 32%, 48%, 64% and 72%. Obtained nanocelluloses were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). FTIR confirms the removal of lignin and hemicelluloses at various stages and total crystallinity index (TCI) was calculated. Similar trend of crystallinity (NC-32, NC-48, NC-64, NC-72: 72.52, 73.83, 76.30, 19.04 %) was observed in XRD analysis. The highest yield of 94.83% was obtained in NC 32 followed by 91.40 and 81.70% for NC-48 and NC-64 and most poor yield was obtained for NC 72~12.03%. AFM and FE-SEM confirms the morphology of obtained nanocellulose and were characterised as three different type of nanocellulose. The NC-32 have web like structure normally observed for cellulose nanofibrills, whereas NC-48 and NC-64 shows rod like particles similar to that of cellulose nanocrystals and NC-72 displayed spherical particles termed as cellulose nanospheres The agglomeration of NCs was related with the low zeta potential (NC-32, 48, 64 and 72; -16.85, -17.84, -5.84, -8.95 mV). The thermal stability of nanocellulose was measured by TGA which suggests NC-64 to have highest thermal stability (>250oC) respective to others. This study has not only explored a novel source in the field of nanocellulose but also developed an understanding on the effect of process parameters on final morphology and characteristics of nanocellulose. This study can help us to carefully design the methodology to tailor the nanocellulose as per end use.