Nanocomposites cut down on chromium waste from making leather

The cost of soft, supple leather shoes and handbags goes beyond the price tag. Chromium tanning agents transform roughly 90% of the world’s animal hides into leather, and a good deal of the chromium ends up in wastewater, where it becomes a hazard. To cut pollution levels, several groups have turned to nanocomposites, which improve chromium uptake into the network of polymerized collagen fibrils that makes up leather. Along those lines, Bin Lyu and Jianzhong Ma of China’s Key Laboratory of Leather Cleaner Production and colleagues now report that pretreating cowhide with vinyl polymer-zinc oxide nanocomposites before tanning improves chromium uptake in the resulting leather. The process also reduces chromium content in wastewater by 50 to 80% (ACS Sustainable Chem. Eng. 2018, DOI:10.1021/acssuschemeng.8b00233). Compared to conventionally tanned samples, the resulting shoe leather has similar durability and softness. Sujay Prabakar of New Zealand’s Leather and Shoe Research Association praised the work but would like to see techniques such as small-angle X-ray scattering employed in the future to learn more about the tanning mechanism and chromium uptake.