Cleaner approach in leather dyeing using graft copolymer as high performance auxiliary: related kinetics and mechanism

Abstract

Solid wastes from leather industry especially trimming waste can be converted to useful auxiliaries for minimization of pollution problems. A copolymer from trimming hydrolysate has been developed using starch and poly vinyl alcohol and is characterized. The application of copolymer at the level of 10% gave improved dye exhaustion of 96%. Optimal operating conditions for dyeing obtained were at pH 5, temperature 60 °C and duration 80 min. Kinetic models have been developed to understand mechanism of adsorption using response surface method supported by design of experiments. Fourier transform infrared spectra analysis showed presence of stretching frequency of hydroxyl groups at the peak of 3278 cm−1 for the copolymer sample. The plausible mechanism for the interaction of -collagen -copolymer-dye- is predicted. The presence of dye and carboxylic reactive sites were confirmed by 13C-nuclear magnetic resonance and mass spectra. These carboxylic acid groups that are present in the co-polymer are responsible in enhancing the adsorption of dye. Emission factors namely, bio-chemical-oxygen-demand and chemical-oxygen-demand have been reduced to the level of 44–66%. The color measurement study showed improvement in dyeing properties. It has been found that copolymer plays a major role in the improving uptake of dye by through active functional groups. This improved dyeing process paves a cleaner way for making sustainable leather production. This method helps to reduce solid waste, especially collagenous waste, generated in leather industry.