Optimization of liquid hot water pretreatment for extraction of nanocellulose crystal from South African waste corncobs

Abstract

This study extracted nanocellulose crystals from South African waste corncobs via liquid hot water pretreatment and alkali treatment. The pretreatment process was designed and optimized using Central Composite Design (CCD) and Response Surface Methodology (RSM), respectively setting temperature (150–200 °C), time (10–60 min), and solid loading rate (3–10% w/w) as input variables. After pretreatment, the residue was treated with sodium hydroxide (2%wt) at 90 °C for 90 min. The extracted nanocellulose crystal was filtered, washed with deionized water, and dried in an oven. The characterization of the nanocellulose crystal was carried out based on standard procedures. The positive correlations between the input variables were observed, whereby a rise in the pretreatment conditions improved the nanocellulose crystal yield. Hence, the study obtained an optimum yield of 55.5% at 200 °C, 10% w/w, and 60 min. The surface morphology showed a more porous and rougher surface, and the crystallinity analysis indicated that run 7 had the most crystalline nanocellulose crystal with a crystallinity index of 57.3%. The study revealed that nanocellulose crystals could be extracted from corncobs via liquid hot water pretreatment and alkali treatment.