Extraction and optimization of Mucuna pruriens for dyeing of leather

The present study reports on the leaching of natural pigment from Mucuna pruriens for dyeing of chrome tanned leather samples. The experiments were performed at temperature (30-70°C), time (30-90 min), feed to solvent ratio (1:3-1:7) and particle size (0.25-0.75 mm) using ethanol as solvent. The influence of process variables on percentage yield has been studied and the conditions were optimized using Box-Behnken design. The optimized conditions for intensified extraction was found to occur at a temperature of 60°C, extraction time of 1 hr, for a feed to solvent ratio of 1:5 and 0.75 mm particle size. The % yield under optimized conditions was found to be 47%. The extraction results were found to agree well with the statistical model (R² = 0.9740). The colouring ability of extracted dye has been tested on wet blue goat leathers. The dyed leather exhibited a better colour value, strength and fastness properties as inferred from reflectance and visual assessment tests.