Evaluation of Ultraviolet Light and Hydrogen Peroxide Enhanced Ozone Oxidation Treatment for the Production of Cellulose Nanofibrils

The oxidation of cellulose to modify the fiber surface is widely recognized as a promising strategy to improve the production of cellulose nanofibrils (CNFs) from pulp fibers. In this study, an eco-friendly advanced oxidation process combining ozone gas, ultraviolet (UV) light, and hydrogen peroxide (H2O2) was proposed and investigated to oxidize cellulose for the production of CNFs from Northern bleached softwood kraft (NBSK) pulp fibers. The results demonstrated that oxidation with the ternary combination of ozone gas, UV radiation, and H2O2 could significantly reduce the degree of polymerization (DP) of cellulose from similar to 1036 to similar to 330 (reduced by about 68%) and increase the content of carboxyl groups from 0.04 to 0.32 mmol/g fibers. Moreover, the oxidation also considerably disrupted the fiber surface. Following high-pressure homogenization, the zeta potential value of the CNFs produced from the oxidized pulps was also much higher (similar to 32 mV) than that of the control (similar to 9 mV). Moreover, the energy consumption during nanofibrillation of the oxidized NBSK pulp fibers (1.52 kWh/kg CNFs) was also significantly reduced by approximately 80% compared to that of the control (6.6 kWh/kg CNFs).