Optimum oxidation for direct and efficient extraction of carboxylated cellulose nanocrystals from recycled MDF fibers by ammonium persulfate

For the first time, this study demonstrates a direct extraction of carboxylated cellulose nanocrystals (c-CNCs) from recycled medium density fiberboard (r-MDF) fibers by ammonium persulfate (APS) without any chemical pre-treatment. The aim of this research was to find an optimum condition for isolating c-CNCs from r-MDF fibers by studying the effect of reaction parameters on the characteristics of c-CNCs. The rod-like c-CNCs had an average length and width of 170 to 365 nm and 13 to 17 nm, leading to an aspect ratio of 13∼21. The optimum conditions for a maximum yield and crystallinity were obtained at a reaction temperature of 70 °C, reaction time of 16 h and APS concentration of 1.5 mol L^˗1. Thermal analysis also revealed lower thermal stability of the c-CNCs compared to r-MDF fibers. The APS oxidation is a viable option for converting r-MDF fibers into value-added c-CNCs.