Walnut shells as cellulose nanocrystal source: isolation procedure and properties characterization

Abstract

The walnut shell is an agro-waste that could be used as nanocellulose source. In the literature, different methods were used to isolate nanocrystals and depending on the method used, spherical or rod like nanocrystals were obtained. The novelty of the current study is the characterization of the crystallinity index, the thermal stability, and the chemical composition, in addition to the geometrical features, of rod like nanocrystals isolated from the walnut shell of “Juglans regia”. The AFM images corroborated that rod like nanocrystals can be isolated using the procedures proposed in the current study. Furthermore, when alkali solution pretreatments were used and the subsequent acid hydrolysis, the isolated CNC showed lower amount of non-cellulosic compounds, and superior L/D and crystallinity index values than CNC isolated directly from walnut shells by acid hydrolysis. The aspect ratio and thermal stability of nanocrystals isolated in the current work are higher than the reported in the literature for other nanocrystals isolated from walnut shells. Finally, the properties of isolated nanocrystals were compared with a commercial cellulose nanocrystal and other nanocrystals reported in the literature.