Investigation of novel deep eutectic systems for the reduction of water usage in leather manufacture

Water in the wet processes of leather manufacture acts as a solvent, transportation medium, support system and is an integral component of the collagen matrix stability at the macro and molecular levels. There have been proposals as to what extent water can be substituted with non-aqueous media, partly due to its role in collagen and processing. As the water content increases from bulk to float water, the system acts as a transport medium for chemical as well as a support system in processing vessels. Here, Deep Eutectic Solvents (DES) are investigated as an alternative solvent system to conventional tanning systems. The novel solvent is non-aqueous, has a high solubility for metal salts, low toxicity, is readily biodegradable and operates at variable temperatures without the release of harmful vapours. These properties make the DES system a potential alternative in leather processing, improving reagent uptake with the potential of lowering effluent discharge. The research focuses on the role of the solvent associated with stabilising collagen, such as the influence of inter- and intra-fibrillar, as well as bulk water, using type 2 DES systems. Thermal, mechanical analysis and electron microscopy were undertaken to determine the effects of the solvent system. The studies indicated that the solvent used, as well as the choice of counter ion, have an important effect on the thermal and mechanical stability of collagen.