TEMPO Oxidation for High Cellulose Content Biomass: A Study on Palm Oil Empty Fruit Bunch Fibers

Abstract Palm oil milling in Colombia generates abundant residual biomass. With a yearly production of over one million tons, empty fruit bunches (EFB) from palm oil extraction can be a valuable source of biopolymers due to their high cellulose, lignin, and hemicellulose contents. We investigate the impact of reaction time, primary oxidizing agent, and a pretreatment process on the physicochemical properties of TEMPO-oxidized cellulose nanofibers (TOCN) derived from palm oil empty fruit bunch (EFB) fibers. Conductometric titrations (CT) and X-ray photoelectron spectroscopy (XPS) were used to determine the total carboxylate contents of nanocellulose and examine the influence of experimental parameters on the EFB-TOCN surface chemistry. Statistical analysis indicates a positive and significant influence of reaction time and primary oxidizing agent on EBF-TOCN degree of oxidation and surface charge density. Partial EFB delignification increased EFB-TOCN oxidation and reaction yield compared to EFB without pretreatment. We also found that only time significantly influences EFB-TOCN hydrodynamic radii, with a reaction length of over 120 minutes required to obtain nanocellulose below 100 nm in size. EFB-TOCN hydrodynamic radii, reaction yield, and oxidation are directly linked to reaction time, primary oxidizing agent amount, and biomass pretreatment process.