Ultrasound-assisted mild sulphuric acid ball milling preparation of lignocellulose nanofibers (LCNFs) from sunflower stalks (SFS)

Abstract

Cellulose nanomaterials have properties that make them renewable materials of choice for various applications. However, the utilization of concentrated alkaline, acids, oxidizing or reducing agents in their production presents significant challenges to the environment. To mitigate this challenge and ensure the efficient industrialization of cellulose nanomaterials, lignocellulose nanofibers (LCNFs) were prepared through an easy, feasible and environment friendly method relative to conventional techniques. 1–3% Sulphuric acid was used in combination with ball milling and ultrasound to produce cellulose nanofibers containing about 92% of the original lignin content. The microstructure and morphology of the nanofibers were studied while thermal analysis showed that the LCNFs can withstand between 225–251 °C and lose only 5% of their weight. Interestingly, despite the binding force of lignin, the nanofibers showed high electrostatic repulsion up to − 47 mV between the fibers. The translucent nanofilms produced from the LCNFs are less hydrophilic having water contact angles around 76°–62°. These LCNFs were synthesised without passing through any pre-treatment process and their hydrophobic properties have been found to be better than conventional cellulose nanomaterials while their thermal properties are comparable.