Adsorption and Kinetic studies of Adhatoda vasica natural dye onto woolen yarn with evaluations of Colorimetric and Fluorescence Characteristics

•In the present study adsorption studies, colorimetric, and emission characteristics of A. vasica natural dye were investigated onto woolen yarn.•Effect of pH on adsorption shows an increase in adsorption capacity with decreasing pH.•Pseudo-second order for kinetics, Redlich-Peterson and Hill isotherm for thermodynamic studies provided best fit to experimental data.•Activation energy was found 69.039 kJ mol−1 indicating chemisorption.•Colorimetric properties and fluorescence characteristics of dyed woolen yarn were found to be improved upon mordanting with different metal salts.

In the present investigation adsorption studies, colorimetric, and emission characteristics of Adhatoda vasica natural dye onto woolen yarn were investigated. Assessment of the effect of pH on dye adsorption showed an increase in adsorption capacity with decreasing pH, with maximum adsorption at pH 3. Pseudo-first order, Pseudo-second order, Elvoich, and Intraparticle diffusion equations were employed to investigate adsorption rates. Pseudo-second order model provided best fit to the experimental data with activation energy of 69.039 kJ mol−1 indicating chemisorption. The equilibrium adsorption data were fitted to Langmuir, Freundlich, Redlich-Peterson, and Hill isotherm models. Redlich-Peterson and Hill isotherm models agreed well with the experimental data having high regression coefficients and least standard deviations for dyeing temperatures of 50, 70 and 90 °C with dye concentration varying from 0.5–20% (o.w.f). A comparative adsorption investigation on silk fiber was presented to understand the better efficiency of woolen yarn. Colorimetric properties and fluorescence characteristics of dyed woolen yarn mordanted with metal salts were generally dependent on chemical nature of mordants and wool-mordant-dye complex forming ability.

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