Feasibility of using hydrothermal treatment combined with washing process and high-shear homogenization to produce chemical-free cellulose nanofiber from lime residue

Chemical-free cellulose nanofiber (CNF) from lime residue (Citrus aurantifolia Swingle) was successfully produced via an environmentally friendly and cost-effective route. Hydrothermal treatment using hot water at 95 °C for 2 h and followed by washing using distilled water for 2 cycles was found to be an effective pretreatment to help remove non-cellulosic components from lime residue. An increase in cellulose content to 31% and a decrease in hemicellulose and pectin content were observed after hydrothermal treatment and washing process. High-shear homogenization at 26,000 rpm for 30 min could deliver the fiber having a diameter smaller than 30 nm. CNF suspension containing 1% total solids content exhibited gel-like behavior, which is a unique property of nanocellulose. Therefore, this study demonstrated the chemical-free pretreatment and alternative mechanical defibrillation for the production of CNF derived from agro-industrial by-products.