Microwave-assisted enhancement of milkweed (Calotropis procera L.) leaves as an eco-friendly source of natural colorants for textile.

Application of natural colorants to textile fabrics has gained worldwide public acceptance due to the hazardous nature of synthetic dyes. Present study investigated the microwave's mediated extraction of natural colorants from leaves of milkweed (Calotropis procera L.) as well as their application to cotton fabrics assisted with biochemical mordants. Dye extraction from C. procera leaves was carried out in various mediums (alkali and aqueous), and the extracted dye as well as cotton fabrics was irradiated with microwaves for 2, 4, 6, 8, or 10 min. Effect of various temperature regimes and sodium chloride (NaCl) concentrations was also evaluated on the color strength of dyed cotton fabrics. The results revealed that extraction of natural colorants was enhanced when microwave radiations were applied for 4 min by using alkali as an extraction medium as compared to aqueous one. Optimum dyeing of cotton fabrics was achieved by using NaCl at a temperature of 55 °C. Among the chemical mordants, iron was effective for better color strength when used as pre- and post-mordant. Among the studied bio-mordants, extract of Acacia nilotica bark significantly improved the color strength and fastness properties as pre-mordant and Curcuma longa tuber as post-mordant. It was concluded that extract of C. procera leaves was a potential source of natural colorants and a high level of dye was obtained upon irradiation of alkali-solubilized extract for 4 min. Application of NaCl at concentration of 3 g/100 mL and temperature treatment of 55 °C significantly improved the color strength of dyed cotton fabrics.