Extraction, Chemical Modification and Characterization of Indigo Dye from Indigofera Tinctoria Leaves and Its Application on Cotton Fabric

Indigofera tinctoria is a tropical plant that has een used to dye cloth since at least 9000 B C but being a natural dye it has poor to moderate fastness. In this study an attempt was made to extract indigo dye from Indigofera tinctoria leaves and carry out its chemical modification by sulphonation to improve its fastness properties when applied on cotton fabric. Indigo exists as a colourless substance which consists of sugar and indoxyl. Indigo dye was extracted from the leaves using an alkali solution (sodium hydroxide solution of different concentrations 2.0M, 3.0M and 4.0M) and acidified hydrogen peroxide to form indigo, the concentrated blue pigment (powdered form). Highest percentage yield of indigo dye powdered form (4.30%) was obtained from using 2.0M sodium hydroxide solution while 3.0M and 4.0M sodium hydroxide solution yielded 3.61% and 3.39% respectively. The characterization of the extracted dye and the modified dye was carried out using UV-Vis spectroscopy and Fourier Transform Infrared (FTIR). Dyeing of cotton fabrics was carried out using the extracted natural dye and the modified dye. Fastness properties was also determined on the dyed fabrics. The result showed that the dyed fabric with modified dye has better fastness properties. Fastness to sun light, fastness to ironing and fastness to washing are 4, 3, and 3 respectively for the modified dye. Dye manufacturing from local plants should be supported using chemical modification procedures to achieve better fastness properties on dyed fabrics.