A comparative study of the suitability of different cereal straws for lignocellulose nanofibers isolation

The aim of this work is to study the suitability of different soda cereal straw pulps (wheat, barley, corn and oats) to produce lignocellulose nanofibers (LCNF). For the study of the influence of the composition and physical characteristics, the pulps were characterized, observing that the physical characteristics do not influence the nanofibrillation process. However, the composition of the fibers plays a key role, mainly the hemicellulose content. The LCNF produced were characterized: chemical structure (FTIR), crystallinity (XRD), thermal stability (TGA), size (DLS) and colloidal stability (ZP). The TO-LCNF are those which presents higher nanofibrillation yields and lower nanofibers size, however presents low crystallinity, thermal stability and a further depolymerization compared to the others LCNF. The lignin contents allow a greater thermal stability (<330°C) than the same size CNF (<250°C). TO-LCNF present more stable suspensions (ZP<-25mV) due to their higher surface charge (COO- groups). AF4 technique was used to effectively determine the size of polydispersed samples of LCNF by avoiding the errors committed by conventional techniques. In addition, it is observed that wheat and barley straws present the most homogeneity in the LCNF samples, being the wheat which presents the best values in the production of LCNF under the three pretreatments.