PRODUCTION OF NANO CELLULOSE FROM NATIVE CELLULOSE - VARIOUS OPTIONS UTILIZING ULTRASOUND

In this study three different ways of applying ultrasound for the production of nanocellulose from native cellulose has been explored. In the first option bleached hardwood kraft pulp was oxidized with the ultrasound catalyzed TEMPO/NaBr/NaOCl-system (US-TEMPO-system) at optimized reaction conditions followed by nanocellulose production by mechanical treatment. The pulp oxidized by US-TEMPO-system at optimum condition has 10%similar to 15% more carboxyls and similar to 10% increase in the nanocellulose yield when compared to the TEMPO-system without sono catalysis. In the second option ultrasound pretreated pulp was subjected to oxidation with TEMPO-system and the oxidized pulp was evaluated for the carboxyls content. No gain in the carboxyls content was obtained in this option compared to the oxidation with TEMPO-system alone even though, scanning electron microscopic analysis showed a higher degree of fibrillation after ultrasound treatment. In the third option US-TEMPO and TEMPO oxidized pulps were subjected to mechanical and ultrasound treatment for the production of nanocellulose. At the same span of time nanocellulose yield was higher in the case of ultrasound treatment compared to mechanical one however, at the same nanocellulose concentration Rheometer Stresstech viscosity of nanocellulose solution was inferior in the former. Observation of the nanofibres under transmission electron microscope showed slightly thinner nanofibrils (diameter - 2-6 nm) in the case of ultrasound treatment compared to mechanical method (diameter - 3-7 nm).