FERROUS-GLUCONIC ACID COMPOUND TANNING: A CLEANER CHROME-FREE TANNING SYSTEM

In order to evaluate the reaction mechanism between Fe2+-gluconic acid compound and collagen, the combination tanning of type-I collagen with Fe2+-gluconic acid compound was studied by UV-Vis spectroscopy, infrared spectroscopy, circular dichroism, and differential scanning calorimetry. The molar ratio for the reaction between Fe2+ and gluconic acid was 1:3. The resulting increased thermal stability could be attributed to crosslinks formed between the compound and collagen. The tanning trials indicated favorable results. The shrinkage temperature observed was 96 degrees C, with tensile strength of about 239 kg/cm, elongation at break of about 63% and tear strength of about 74 kg/cm. The leather tanned with the Fe2+-gluconic acid compound was lighter in color compared to the single ferrous sulfate (Fe(II)) tanning system, and had neither a darkening of color nor a reduction in strength properties. It was also clear that COD and TS loads were decreased by 26.5% and 29.8%, respectively compared to Fe(II) system, 7.3% and 26.1%, respectively, compared to BCS system. Studies show that the disadvantages connected with Fe(II) tanning system including loss of strength and darkening of color have been solved successfully.