Studies on the Acid Hydrolysis of Chamois Leather Wastes

The present paper aims to investigate a hydrolytic method, feasible to be applied at industrial level, to turn into useful products the Chamois leather wastes, mainly the buffing dust. The efficacy of acid treatments with 0.3, 0.5 and 1.0 % HCl solutions, by autoclaving at 105 °C, for reaction times of 6, 10 and 14 hours, was determined in an attempt to optimize the hydrolysis parameters. Based on the mass balance of performed experiments, the yields of hydrolysis processes were calculated for two of the products that were separated from the final mixture: collagen hydrolysates and fats. Optimal working parameters were: a concentration of 0.5 % HCl, and a duration of 10 hours, by simply boiling in autoclave, at 105 °C. The resulted polypeptides mixture was characterized by chemical (total nitrogen content) and physical-chemical methods (FTIR spectra, EDAX). The recovered greasy matters were purified by water-solvent partition, and the specific physical-chemical indicators were determined. The main advantage of the polypeptide mixtures obtained by Chamois wastes hydrolysis consists in the fact that they are chromium-free, and can be used for a large range of industrial (foaming agents, waste water treatment, chemical auxiliaries, fillers, adhesives, blends with synthetic polymers, concrete mixtures etc.) and agricultural applications (nitrogen and sulfur slow release fertilizers, animal feeding). The grease fraction can be used in leather wet finishing, or can be further chemically modified to produce surfactants. The small amounts of solid residues which resist to the acidic hydrolysis can be used, after neutralization, as additives of concrete mixtures, in producing decorative bricks.