Properties and Application of Re-generated Vegetable Tanning Agent

For fully utilizing the phenolic substances in vegetable tanning effluent and reducing effluent discharge during vegetable tanning process, the effluent was sulfonated with sodium sulfite at first, and then formaldehyde was used to crosslink to prepare re-generated vegetable tanning agent (RVTA). Then the similarities and differences between bayberry extract and RVTA were compared in terms of component, combination ability, penetration and tanning properties. RVTA was used in tanning process with bayberry extract, and the performances of tanned leather were also tested. The results showed that there was more non-tannin composition but less tannin composition in RVTA and it had weak combination ability and stability with collagen together with slightly poor permeability. However, shrinkage temperature of hide powder tanned by RVTA could reach 81.2 ℃ when tannin content was 8 g/L. By using RVTA together with bayberry extract in vegetable tanning process, the tear strength and shrinkage temperature of the leather was better, and the tensile strength, elongation, grain and cross-section morphology were comparable with leather tanned by bayberry extract. This work would provide a reference for vegetable tanning effluent recycling and cleaning process of vegetable tanning.