An approach on sustainable leather production system and method: Chromium tanning in vacuum operated reaction vessel for sheepskins

Conventional leather chromium tanning requires long process time, excessive water usage and results in low float exhaustion of chrome salts. Our study aimed to eliminate the negative aspects of chromium tanning by designing a vacuum operated reaction vessel/drum and suitable production recipe for sheepskins. Tanning time decreased from 10 h to 6 h under vacuum. Float uptake was increased almost 30% according to the chrome oxide (Cr₂O₃) contents in leather and residual floats. Using the process water was also considerably saved. Process success was proved with Cr₂O₃ contents in leather and wastewater by chemical analyses after tanning operations. Shrinkage temperature (T_s) controls as hydrothermal stability indicator of collagen were also realized on the tanned skins. Pollution loads of conventional and vacuum operated chromium tanning were discussed with chemical oxygen demand (COD), total suspended solids (TSS), conductivity and salinity in the tanning baths. Physico-mechanical properties were also compared of the final products by tensile strength and tear load analyses. The results showed that vacuum operated chromium tanning was highly effective and promised for the sustainable production of leather products.