Extraction, Characterization and Usage of Dyes from Mango Rinds

Abstract

Dyes are substances used to colour fibres and fabrics in everyday applications and are broadly classified as natural or synthetic. Increasing environmental and health concerns associated with synthetic dyes have intensified interest in sustainable, eco-friendly alternatives. This study investigates the extraction, characterization, and application of natural dyes derived from discarded mango rinds, an abundant agricultural waste. Mango rinds were sourced from consumers and fruit vendors in Ogbomoso, then washed, dried, pulverized, and subjected to aqueous and hydrothermal extraction. The resulting dyes were characterized using ultraviolet-visible (UV-Vis) spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy to determine their optical and chemical properties. Dyeing experiments were conducted on cotton and silk fabrics using alum and lime as mordants. The dyed samples were evaluated for colour fastness to water, detergent, and sunlight exposure. Results indicate that mango rinds yield appreciable natural dyes with distinct colour intensities. UV-Vis analysis suggests the dominance of carotenoid pigments, while FTIR confirms the presence of functional groups such as hydroxyl, carbonyl, and nitro compounds. The colour shades varied with mordanting conditions and exhibited moderate to good fastness properties. Cotton fabrics showed better dye retention compared to silk. However, excessive mordant concentration, particularly with alum, adversely affected fabric strength and led to degradation. The study demonstrates that mango rind is a viable, sustainable source of natural dye, contributing to waste valorisation. Further research on purification, large scale production, and application on diverse substrates is recommended to enhance industrial viability.