Extraction of natural dye from the mesocarp and exocarp of Cocos nucifera, textile dyeing, and colour fastness properties

Abstract

Dyes derived from coconut (Cocos nucifera) husk have materialised as an important substitute to synthetic dyes. However, better extraction techniques are needed to leach out the natural colourants from this plant. The influence of sodium hydroxide (NaOH) concentration (0.2 to 0.8 M) and time of extraction (2 to 10 min) on the maximum extraction yield of natural dye from the mesocarp and exocarp of C. nucifera have been studied. The results indicate a significant (p < 0.05) increase in dye yield for both mesocarp and exocarp extracts when using 0.8 M NaOH for 4 min. This study had also investigated the effect of different concentrations of tannic acid as a mordant on dyeing properties and wash fastness of cotton fabrics dyed with the mesocarp and exocarp C. nucifera dyes. The dyeing process of the natural dye was performed by varying the concentrations of tannic acid (2.5%, 5.0%, and 7.5%) at 40 °C for 60 min. Pre-mordanted dyed cotton fabrics showed a deeper colour than unmordanted dyed cotton fabrics. As the concentration of tannic acid increases, the L* value decreases in all pre-mordanted fabrics. Tannic acid as a mordant exhibited better result at 7.5% concentration than the 2.5% and 5.0% concentration. The darkness and shade of the dye from the mesocarp exhibited a better outcome than the exocarp of C. nucifera and confirms that the mordant enhanced the dye hue on cotton fabric. Wash fastness properties of mesocarp dyed cotton fabrics ranged from poor (2) to good (3) depended on the tannic acid concentration used. This work suggests that mesocarp C. nucifera dye can complement synthetic dyes in the dye industries.