Sustainable leather making - An amphoteric organic chrome-free tanning agents based on recycling waste leather

Dongyu Hao; Xuechuan Wang; Shuang Liang; Ouyang Yue; Xinhua Liu; Dongyan Hao; Xugang Dang

doi:10.1016/j.scitotenv.2023.161531

Sustainable leather making - An amphoteric organic chrome-free tanning agents based on recycling waste leather

Sci Total Environ. 2023 Apr 1:867:161531. doi: 10.1016/j.scitotenv.2023.161531. Epub 2023 Jan 10.

Authors

Dongyu Hao¹, Xuechuan Wang², Shuang Liang³, Ouyang Yue¹, Xinhua Liu³, Dongyan Hao⁴, Xugang Dang⁵

Affiliations

¹ College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi 710021, PR China; Institute of Biomass and Function Materials & National Demonstration Centre for Experimental Light Chemistry Engineering Education, Xi'an 710021, PR China.
² College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi 710021, PR China; College of Bioresources Chemistry and Materials Engineering, Shaanxi University of Science and Technology, Xi'an 710021, PR China. Electronic address: wangxc@sust.edu.cn.
³ Institute of Biomass and Function Materials & National Demonstration Centre for Experimental Light Chemistry Engineering Education, Xi'an 710021, PR China; College of Bioresources Chemistry and Materials Engineering, Shaanxi University of Science and Technology, Xi'an 710021, PR China.
⁴ School of chemical engineering and modern materials, Shangluo University, Shangluo 726000, PR China.
⁵ Institute of Biomass and Function Materials & National Demonstration Centre for Experimental Light Chemistry Engineering Education, Xi'an 710021, PR China; College of Bioresources Chemistry and Materials Engineering, Shaanxi University of Science and Technology, Xi'an 710021, PR China. Electronic address: xg.dang@sust.edu.cn.

PMID: 36638976
DOI: 10.1016/j.scitotenv.2023.161531

Abstract

Currently, globally, 90 % of the tannery is still tanned by using chrome, resulting in chromium-containing wastewater and chromium-containing solid waste that will cause serious harm to the environment. Under the pressure of environmental protection, on the one hand, the leather manufacturing industry should to dispose the current problem of chromium pollution, especially chromium-containing solid waste (chromium-containing waste leather (CCWL)), on the other hand, to popularize chrome-free tanning agent. Organic chrome-free tanning agents are the way forward for chrome-free tanning agents. However, organic chrome-free tanning agents exhibit several limitations with respect to their preparation and applications: The preparation process is not eco-friendly, and physicochemical properties of tanned crust leather are poor. More importantly, the leather tanned by an organic chrome-free tanning agent has low absorptivity of traditional anionic wet finishing materials, resulting in high total dissolved solids in tannery wastewater, which increased the difficulty of tannery wastewater treatment, and posed a potential threat to the environment. In this study, collagen polypeptide (CP) was extracted by using in situ dechromization and industrial trypsin from CCWL, followed by modification with ethylene glycol diglycidyl ether (EGDE) to obtain an epoxy-terminated, biomass-based, amphoteric organic, chrome-free tanning agent (CP-EGDE) with a high isoelectric point of 5.16, and an epoxy value of 0.316 mol/100 g. CP-EGDE can be applied in the pickling-free and salt-free tanning processes to prepare wet white leather and the tannery wastewater with good degradability. The shrinkage temperature (T_s = 84.9 °C), grain flatness, fullness, softness, yellowing resistance, mechanical properties, absorptivity of traditional anionic fatliquor (88.4 %) and dyes (95.3 %) of CP-EGDE tanned leather exceeded those of commercial organic chrome-free tanning agents. This research considered both environmental protection and leather quality, especially greatly improving the absorptivity of traditional anionic wet finishing materials. CP-EGDE is expected to replace chrome tanning agents and has good application prospects.

Keywords: Amphoteric; Biomass-based; Chrome-containing waste leather; Chrome-free tanning agent; Leather manufacturing industry; Sustainable.