Upcycling coconut husk coir by extraction of cellulose nanofibrils using green citric acid from lemon juice

Abstract

An eco-friendly approach to nanocellulose extraction from coconut husk waste is presented, utilizing natural lemon juice for acid hydrolysis instead of conventional sulfuric acid. This environmentally benign method reduces cost and safety concerns associated with chemical processing while offering a sustainable alternative to petroleum-derived acids. Coconut husk, a widely available agricultural waste, poses environmental hazards due to landfill overflow, contributing to pest proliferation and disease outbreaks. In this study, cellulose nanofibrils (CNFs) extracted using lemon juice were characterized by Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), and zeta potential analysis. The FTIR spectra confirmed the effective removal of hemicelluloses and lignin, while XRD analysis revealed a crystallinity index of 37%, indicating successful nanofibril isolation. SEM imaging demonstrated the fibrillar morphology of the extracted CNFs, while zeta potential measurements confirmed their colloidal stability. Compared to sulfuric acid-derived CNFs, the lemon juice-extracted nanofibrils exhibited comparable physicochemical properties, validating this green alternative. The findings support sustainable waste management and circular economy principles by promoting the valorization of agricultural residues into high-value nanocellulose. Potential applications include its use as a reinforcement material in biodegradable packaging, biomedical scaffolds, and environmentally friendly nanocomposites. This study aligns with several United Nations Sustainable Development Goals (SDGs), particularly those related to responsible production, sustainable consumption, and reduced dependency on fossil-based resources.