Use of Ternary Solvent (Water - Ethanol - Ethyl Acetate) Medium for Leather Processing: A Possible Paradigm Change

An attempt to replace water (7-10 m(3)/ton) in leather processing with a ternary mixture of solvents that would have a lower boiling point than water (for easy recovery through evaporation) and also bring about maximum solubility of conventional dyes, syntans and fatliquors is reported. The ternary mixture (Water ethanol ethyl acetate) reported in this study provided for good solubility/dispersion of leather chemicals. Average particle size of the syntan/dye in solvent / water remaining the same, particle size distribution of dyes and syntans was advantageous in the solvent medium, leading to better diffusion. Amongst various trials, neutralization of the leathers after tanning in solvent medium followed by use of neutralization syntans was found to be more advantageous to obtain leather properties comparable to conventional controls. The adsorption studies of dye used in the present study followed Freundlich model in both solvent and water medium indicates multilayer adsorption. Physical properties of the leathers were similar to that of control, indicating clearly that the solvent had no adversary effect on collagen and also provided for good diffusion and fixation of chemicals. The method thus reported in this study could provide for a minimum change approach to leather processing with ample contribution to water saving.