Mixed metal tanning using chrome-zinc-silica: A new chrome-saver approach

Development of newer tanning agents is necessary to overcome the ecological pressure arising from the present tanning methods. Research of such nature will also lead to the evolution of better tanning systems. In the present work, a tanning system based on the mixed metal complexes of chromium, zinc and silica have been prepared. The percentages of chrome, zinc and silica in the tanning system have been optimized based on the properties like hydrothermal stability, physical strength characteristics and percentage exhaustion of chromium. Tanning agents with various ligand environments have been prepared so as to obtain an effective combination for tanning. Hydrothermal stability of the leathers is about 95degreesC and the percentage exhaustion of chromium is about 90%. The strength and organoleptic properties of the leathers tanned with this new tanning system are on par with and/or better than the conventional chrome tanned system.