Sustainable eco-friendly extraction of yellow natural dye from haar singhar (Nyctanthes arbor-tritis) for bio coloration of cotton fabric

The revival of natural dyes in different walks of life is due to stringent environmental standards imposed by many associations. For current studies, flowers of haar singhar (Nyctanthes arbor-tritis) has been chosen for bio-dyeing of cotton fabric using microwave irradiation techniques. For this purpose, liquid extracts and fabrics were exposed to microwave for 5 min at various conditions. These treated and un-treated dye extracts obtained in respective media were employed to dye the radiated and non-radiated cotton fabrics. The characterization of extract and untreated and undyed irradiated fabrics samples was done through FTIR. Different dyeing variables were optimized under CCD response surface methodology as a statistical tool. With the introduction of new shades and improvement of colorfastness properties, different concentrations of sustainable chemical and bio-mordant were employed. All dyed cotton fabrics were exposed to CIE-color space system for estimation of color coordinates and color strength by using spectra flash SF600 and to rate colorfastness properties using ISO standard methods for light, dry and wet rubbing, washing fastness. Cotton fabric was dyed with haar singhar flower extract of 7 pH from 4 g of powder, using 1.5 g/100 mL salt solution at 60 degrees C for 30 min. To get acceptable shades, aqueous extract after microwave treatment for 4 min provided excellent color strength. Pistachio (K/S = 3.6342) is a bio-mordant with great results, and aluminum (K/S = 4.8205) is a chemical mordant with outstanding results. It is found that green methods for isolation of colorant and green mordants for getting new shades should be employed.

Automated summary

The revival of natural dyes in various industries is a response to the strict environmental standards imposed by associations. In this study, the flowers of haar singhar were used for dyeing cotton fabric using microwave irradiation techniques. The results showed that microwave treatment improved the color strength of the dye extracts, and the use of bio-mordant and chemical mordant enhanced the dyeing effect.