Tanning is the process of treating skins and hides of animals to produce leather. The tanning process prevents bacterial attack, increases leather’s strength, and produces a soft, durable and, flexible material. Chromium, iron, aluminum, titanium, and zirconium are commonly used inorganic tanning agents in the leather industry.
Chrome tanning is widely employed because of its high shrinkage temperature property and tensile strength. However, certain limitations of chromium tanning agents have led to the usage of its substitute. Limitations include lack of fiber compaction and high environmental hazards. Furthermore, some countries have imposed stringent limits upon the quantity of chromium emanating from tanneries that is discharged in the environment through liquid and solid wastes.
The chromium salt tanning system is under continuous pressure from environmental groups and international regulatory bodies due to pollution and toxicity. This has resulted in the development of new tanning agents intended to partially or completely replace chromium salts. Research and development has been directed toward the development of alternative tanning processes. For instance, alternative mineral tanning salts based on aluminum, titanium, zirconium, iron, and silica were developed. Implementation of cost-effective processes that enable the production of leathers bearing similar properties to those of conventional chrome tanned stock led to the usage of iron or zirconium. Zirconium was the preferred choice, as iron has poor strength and color drawbacks. Therefore, zirconium was the potential alternative to replace chromium in tanning.