Cellulose isolation from coconut husk by single step process using hydroperoxy-citric acid

Agricultural waste, specifically coconut husk, presents an abundant and underutilized source of lignocellulosic biomass, particularly in tropical regions. This study introduces a novel, single-step, halogen-free method for isolating cellulose from coconut husk using hydroperoxy-citric acid (HPCA), a sustainable alternative to conventional harsh chemical processes. The isolated cellulose at varying HPCA concentrations (20%-100%) was extensively characterized. Results showed that the highest cellulose yield (82.38%) was achieved at 20% HPCA. As shown by XRD results, Cellulose2 achieved 45.79% crystallinity index and a crystallite size of 5.40 nm. FTIR analysis confirmed the effective removal of lignin and hemicellulose across all concentrations, as evidenced by the absence of C C functional group in cellulose isolated. SEM images, illustrating a morphological shift from intact cellulose to a more homogeneous, dense, and less porous matrix of cellulose, ultimately obscuring individual fibers which isolated by higher HPCA concentrations. The thermal analysis of coconut husk and coconut husk cellulose was evaluated. The TGA data revealed an initial 8.5% and 7% weight loss from water evaporation at a temperature around 90 °C for coconut husk and coconut husk cellulose, respectively. Furthermore, TGA analysis indicates that coconut husk and coconut husk cellulose begin to degrade at 200 °C. Coconut husk cellulose degraded at a higher temperature (360 °C) compared to coconut husk (346 °C). The DSC results confirmed the natural cellulose characteristics through an endothermic peak with a heat flow of −59.72 J/g, and DMA analysis confirmed the viscoelastic properties of coconut husk and cellulose. This research validates the HPCA method's efficacy for sustainable cellulose isolation. Furthermore, the isolated cellulose can be used as a filler material in the manufacture of biocomposites.