Processing of Leather Using Deep Eutectic Solvents

Abstract

Processing of 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. The current study shows that a variety of deep eutectic solvents, DESs may be used for the tanning, fatliquoring and dyeing of animal hides, being particularly useful for mineral (chromium) and vegetable tanning processes. The tanning agents are able to penetrate rapidly into the hide, driven by lyotropic swelling due to their high ionic strength. The samples are shown to have similar tanning agent content to the currently used aqueous chromium (III) sulfate solution, however the waste metal content is shown to be significantly reduced. Incorporation of the DES Ethaline into the leather significantly alters the swelling properties of the leather increasing the flexibility and ductility of the material, therefore acting in the same manner as a fatliquor which lubricates or plasticises the fibrous structure of the collagen. Ethaline was also used to transport a lysochromic dye throughout the cross-section of the leather, and the hydrophobicity of the dye prevents leaching into the aqueous wash solution. Physical measurements show that leather processed using DESs have similar mechanical properties to that processed using conventional aqueous systems.

Thermodynamics of phase transfer for polar molecules from alkanes to deep eutectic solvents

“…The partition coefficients between decane and 1 ChCl: 2 EG are shown in Table 5. It can be seen from High solubilities have previously been observed for large molecules such as lignin [27] and vegetable tans [28] in DESs. This presumably because of the large enthalpy of solvation resulting from the solute having a large number of hydroxyl functional groups.…”

Globular and Fibrous Proteins Modified with Deep Eutectic Solvents: Materials for Drug Delivery

“…Results show that initially, the IL monomers interact with gelatin at the interface but at higher concentrations hydrophobic micro domains were observed. A study by Alaysuy investigated the effect of DESs on collagen in leather [30]. Results showed that the DES did not denature the collagen structure but was absorbed into the macroscopic pores and could be forced out of the structure with applied pressure, i.e., the DES did not change the crystalline structure of the collagen.…”

Current trends in leather science

“…This has been demonstrated as a useful option for both chrome and vegetable tanning [61,62]. However, the more exciting aspect is the possibility of using chemistries currently not possible, for example introducing graphite deep into the collagen structure.…”