The new ‘ion’ age – revolutionary new technology for leather manufacture?

Processing leather has an historical reputation as a chemically and energetically intensive process which produces large volumes of aqueous waste. Saline pollution combined with heavy-metal, dyes and acid and base streams make leather production an ecologically sensitive industry. Deep eutectic solvents (DESs) have been used for a range of other applications and removed the use of water in those systems. This presentation introduces DESs and demonstrates how they can be used for the tanning, fatliquoring and dyeing of animal hides drastically reducing water requirements when compared with current technology. It is shown to be useful for both mineral (chromium) and vegetable tanning processes. The tanning agents are able to penetrate rapidly into the hide which are shown to have similar tanning agent content to the hide tanned using a traditional aqueous chromium (III) sulfate solution. Incorporation of the DES into the leather can act in the same manner as a fatliquor which lubricates or plasticises the fibrous structure of the collagen. The DES can also be used to carry a lysochromic dye throughout the leather and the hydrophobicity of the dye means that it does not leach into an aqueous wash solution. Physical measurements show that leather processed using DESs have similar properties to that processed using conventional aqueous systems.