Coconut Husk Fiber: A Low-Cost Bioresource for the Synthesis of High-Value Nanocellulose

Nanocellulose has recently gained a foothold of significance among nanomaterials due to its unique properties, including renewability and sustainability. In this study, two promising methods, steam explosion and alkali-acid hydrolysis, were evaluated for the cellulose extraction from coconut husk fiber. Between the two methods, alkali-acid hydrolysis yielded 1.8 times higher cellulose content than the other. Hence, cellulose was obtained through the alkali-acid hydrolysis method to synthesize Nano-Crystalline Cellulose (NCC). In order to maximize cellulose content in nanocellulose synthesis, acid concentration, reaction temperature, and hydrolysis time were optimized using Response Surface Methodology (RSM). The optimum reaction condition for the synthesis of NCC was 50 °C with 45 wt% acid concentration for 60 minutes due to its high cellulose content (85.6 %). Synthesized NCC was spherical in shape with a diameter below 40 nm. NCC had better crystallinity (80.05 %) with a high zeta potential of -72.2 mV. NCC was evaluated for its adsorption capacity for different dyes at varying pH levels. Among the dyes, the removal efficiency of NCC was higher for methylene blue (90.89 %) and congo red (89.96 %) at all pH levels. But adsorption of crystal violet dye by NCC was higher in alkaline pH (9) and methyl red in acidic pH (5). As a result, synthesized nano cellulose could be used in the removal of synthetic dyes from textile effluents.