Eco-friendly Synthesis of Silver Nanoparticles Using Anacardium occidentale Juice and their Deposition on Cellulose Derived from Agricultural Residues

Abstract

This study investigated an eco-friendly route for producing silver nanoparticles (AgNPs) and immobilising them on cellulose recovered from coconut coir, an agricultural residue. Cellulose was extracted from Cocos nucifera coir through alkali treatment, acid treatment and bleaching. Juice obtained from Anacardium occidentale cashew apples was used as the bioreducing medium for AgNP synthesis from a 5 mM silver nitrate solution under microwave irradiation. The AgNPs, pristine coir fibre cellulose (CFC) and AgNP-coated cellulose nanocomposite (AgNPs@CFC) were characterised using ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. AgNP formation was indicated by a visible colour change and a characteristic absorption maximum at 432 nm. The infrared spectra supported the effective removal of lignin and partial removal of hemicellulose during cellulose extraction and showed changes associated with AgNP deposition. X-ray diffraction confirmed the retention of the cellulose I crystalline phase after nanoparticle deposition and identified a characteristic silver reflection at 46.44°. The crystallinity indices of CFC and AgNPs@CFC were 63% and 64%, respectively. Scanning electron micrographs showed a fibrous cellulose morphology and well-dispersed AgNPs on the cellulose surface. The findings demonstrate a practical green synthesis approach that combines cashew apple juice and coconut coir cellulose for agricultural-waste valorisation. Application-specific testing is required before the nanocomposite can be validated for pollutant removal, antimicrobial use or packaging.