Evaluation of eco-friendly cellulose and lignocellulose nanofibers from rice straw using Multiple Quality Index

Huge amounts of rice straw are left every year in different areas of the world; these residues still cause environmental problems due to un-safe practices such as burning. Isolation of nanomaterials such as cellulose nanofibers represents an effective way for utilization of rice straw in advanced products. The current work aimed at evaluating the properties of rice straw cellulose nanofibers isolated from bleached and high-lignin unbleached pulps using a multi-criterion quality index, which allows a benchmarking analysis between different sources, processes and features. Rice straw was subjected to neutral sulfite pulping process to obtain the high-lignin unbleached pulp while the bleached pulp was obtained by bleaching the produced pulp with NaClO2/acetic acid mixture. Using mechanical pretreatment (Valley beater), and ultrafine friction grinder both bleached and unbleached pulps were used to obtain cellulose nanofibers with and without lignin (L-CNF and CNF, respectively). Nanopaper sheets were prepared from both types of nanofibers and characterized using tensile tests, optical microscopy, atomic force microscopy, electron scanning microscopy, water contact angle and surface energy. Cellulose nanofibers generated from rice straw were scored using a multi-criterion quality index depending on characterization using eight tests (nanosized and macro size fraction, turbidity, Young's modulus, porosity, transmittance, tear resistance, and homogeneity).