Synergic effect of tungstophosphoric acid and sonication for rapid synthesis of crystalline nanocellulose.

The utilization of sonication in combination with tungstophosphoric acid (PWA) catalyst reduces dramatically the time of operations from 30h to 10min by using an optimum sonication power of 225W. The basic cellulosic structure is maintained, allowing preparing high-quality nanocellulose. The size of the nanocellulose obtained was in the range from 15 to 35nm in diameter and several hundred nanometers in length, with a high crystallinity of about 88%. The nanocellulose shows a surface charge of -38.2mV which allows to obtaina stable colloidal suspension. The surface tension of the stable, swollen aqueous nanocellulose was close to that of water. These characteristics, together with the fast procedure allowed from the synergic combination of PWA and sonication, evidence the high potential of the proposed method for the industrial production of nanocellulose having the properties required in many applications.