TANNING STUDIES WITH BASIC CHROMIUM SULFATE PREPARED USING CHROME SHAVINGS AS A REDUCTANT: A CALL FOR 'WEALTH FROM WASTE' APPROACH TO THE TANNING INDUSTRY

摘要

Leather processing is associated with the generation of both solid and liquid wastes. Various in plant as well as end-of-pipe treatment methodologies are available for the management of liquid wastes. Although several options do exist for handling solid wastes, the presence of chromium causes concern for many of the applications. Chrome shavings contribute to almost 10% of the solid wastes generated from processing raw hides/skins. In this study, chrome shavings have been advantageously used as a reductant for the manufacture of basic chromium sulfate thereby providing a comprehensive closed cycle. Two BCS products developed with chrome shavings alone for reduction (complete replacement of molasses, product A) or partial replacement of molasses (product B) have been employed for tanning of goatskins. Studies reveal that the quality of the wet blue leathers is on par with the leathers tanned with commercial BCS. Shrinkage temperature of the leathers is comparable and is above 100℃ at an offer of 1.25% Cr_2O_3. Chromium exhaustion is in the range of 75 - 80% with 1318-1490 ppm of chromium in the spent tan liquor. Wet blue leathers tanned with product A possess more fullness among all the leathers, which may be due to the presence of intermediate protein products formed during BCS preparation. This is further confirmed with the scanning electron microscopic analysis. Performance of the crust leathers is comparable to that of conventional tanned leathers in spite of reduction in syntans by 20%. This methodology provides a means for recovering wealth from waste.