A smart high chrome exhaustion and chrome-less tanning system based on chromium (III)-loaded nanoparticles for cleaner leather processing

Currently, chromium-containing wastewater from tanning process has seriously restricted the sustainable development of the leather industry. This problem can be solved by high-exhaustion chrome tanning technology and chrome-less tanning technology. However, these techniques not only fail to achieve a uniform tanning effect but also reduce the performance of the leather. In this work, pH-sensitive and chromium (III)-loaded nanoparticles were fabricated by self-assembly of poly [poly (ethylene glycol) methyl ether acrylate-co-acrylic acid-co-glycidyl methacrylate (PEGMA-co-AA-co-GMA)] terpolymers templated Cr(OH)(3) mineralization, which were defined as Cr-PPAG NPs and utilized as smart high chrome exhaustion and chrome-less tanning agents. Due to the core-shell structure, these Cr-PPAG NPs exhibit a 'Trojan horses' behavior which can protect Cr3+ from reacting with skin collagen during the penetration process, leading to effective and uniform delivery of Cr3+ to the rawhide's interior. Then, the released Cr3+ from Cr-PPAG NPs could cross-link the carboxyl groups both on the skin collagen and poly (PEGMA-co-AA-co-GMA), thereby producing the high-exhaustion chrome tanning effect. Furthermore, the GMA moieties of poly (PEGMA-co-AA-co-GMA) could further react with amino groups of collagen fiber. The synergy between chrome tanning and the organic tanning effects provided by Cr-PPAG NPs resulted in a chrome-less tanning technology. Finally, the final leather tanned with Cr-PPAG NPs exhibiting improved hygienic characteristics with excellent antiadhesive properties against E. coli and S. aureus bacterial strains. (C) 2020 Elsevier Ltd. All rights reserved.