Modified ammonium persulfate oxidations for efficient preparation of carboxylated cellulose nanocrystals

Ammonium persulfate (APS) was able to produce carboxylated cellulose nanocrystals (CNCs-COOH) directly from the raw materials of cellulose. However, the industrial production of CNCs-COOH by this method is obstructed by the lower preparation efficiency. Herein, by the activation via N,N,N’,N’-tetramethylethylenediamine (TMEDA) and ultrasonic assisted disintegration, modified APS method to extract CNCs-COOH from pulp was presented. A high yield (up to 62.5 %), low usage of APS (8.5 g APS per gram pulp) and less reaction time (6 h) was achieved. The as-prepared CNCs-COOH exhibited high carboxyl group content (1.45 mmol/g) and high crystallinity index of 93 %. The reaction mechanism has been studied, and the results show that with the addition of TMEDA, S2O82–can be converted to free radicals and hydrogen peroxide more quickly. Our studies suggested that modified APS method may be a suitable and economic alternative for the preparation of CNCs-COOH.