Efficient extraction of carboxylated spherical cellulose nanocrystals with narrow distribution through hydrolysis of lyocell fibers by using ammonium persulfate as an oxidant

An efficient and low-cost approach to prepare spherical cellulose nanocrystals (SCNCs) is presented through chemical hydrolysis of lyocell fibers in an ammonium persulfate (APS) solution. The as-prepared cellulose nanoparticles were characterized by scanning electron microscopy, atomic force microscopy, laser light scattering particle analysis, wide angle X-ray diffraction, Fourier transform infrared spectrometry and thermal gravimetric analysis. Effects of hydrolysis conditions, such as reaction time and temperature, and APS concentration on the morphology, microstructure, and thermal stability of cellulose nanoparticles are discussed. Moreover, it is found that under mild reaction conditions, cellulose nanoparticles are spherical particles with a narrow diameter distribution, and have a cellulose II polymorphic crystalline structure with surface carboxyl groups. The optimal hydrolysis time was found to be around 16 h for hydrolysis at 80 °C with a 1 M APS aqueous solution.