Environmentally-friendly tanning for leather production: a review

Traditional industrial methods of the leather industry produce toxic chromium-containing wastewater and solid wastes, calling for alternative procedures. Here, we review greener technologies to produce leather with focus on principles to design materials, high-efficiency chrome tanning, chrome-free processes, e.g., organic tanning, combination tanning, nanomaterial-based tanning, and tanning agent-free technology, as well as high-performance post-tanning using multifunctional polymers, integrated tanning-dyeing systems, and socioeconomical aspects. High-efficiency chrome tanning is done by high-exhaustion chrome tanning or inverse chrome tanning, which reduce the usage of chrome. Organic tanning employs biomass-derived and polymeric tanning agents.