Free of water tanning using CO2 as process additive—An overview on the process development

Leather is a product traded worldwide. The majority of leathers are cattle skins tanned by using chromium-III salt, which are in the focus of this work. The article describes the shortening of tanning time by using compressed carbon dioxide as process additive from 30 to 5 h in lab-scale (63 mL autoclave). In pilot-scale (20 L autoclave) a tanning process practically free of wastewater is demonstrated. Compared to conventional processes less chromium-III salt is used and the process time can be reduced to 2.5 h. Some underlying principles for the process intensification caused by carbon dioxide are described. The article concludes with first results from a demonstration plant of technical size with a volume of 1700 L, which is able to tan a mass of up to 700 kg (>100 m2) per batch in a rotating drum.