Optimal Conditions for Isolation of Nanocrystalline Cellulose Particles

Nanocrystalline cellulose particles are new class of cellulose materials that can find the wide application in various technical areas, biotechnology and medicine. The nanoparticles are usually made by treatment or initial cellulose samples with concentrated sulfuric acid (SA) at various temperatures and following mechanical or ultrasound disintegration. Unfortunately, conditions of existing methods for preparation of nanocellulose are multifarious and give both crystalline and amorphous nanoparticles. Therefore in this paper the optimal conditions for obtaining just of nanocrystalline cellulose particles (NCP) have been studied. The experiment showed that isolation of NCP is carried out in narrow interval of the acid concentration: from 50 to about 61 wt. %. If concentration of SA is less than 50 wt. % then micro-scale particles are isolated. On the other hand, if concentration of SA is higher than 63 wt. % the cellulose completely dissolves, and as a result instead of nanocrystalline the amorphous particles are formed with decreased yield. In the range of the acid concentration from 55 to 61 wt. %, a low decrystallization of the initial cellulose is taken place that contributes to forming of rod-like nanocrystalline cellulose particles. The following optimal conditions of the acidic treatment for isolation of NCP were proposed: concentration of sulfuric acid 57-60 wt. %, acid to cellulose ratio 8-10, temperature 45-55 C, time 40-60 min. These optimal conditions in combination with the high-power disintegration permit obtaining the rod-like nanocrystalline cellulose particles (150-200 x 10-20 nm) with the increased yield (70-75%).