Melamine-Based Polymeric Crosslinker for Cleaner Leather Production

To augment sustainable tanning, less chrome input, high functional quality leather processed via no restricted substance in processing, and ease to treat the inevitable protein waste generated are the key challenge, and currently, they have become the active part of leather research. Our work covers the synthesis of a formaldehyde-free chromium-incorporated polymeric tanning agent (FF-CIPTA) and its application in a reformed leather processing route which ensures near zero discharge of chromium containing solid waste. The preliminary characterization of FF-CIPTA reveals that the developed product is stable up to pH 5.2, and the particle size distribution ranges from 955 to 1450 nm with 12% Cr₂O₃ content. The present work significantly reduces the tanning agent input without compromising the thermal stability (103 °C) of the leather because of its multicrosslinking nature. Since the product exhibits a polymeric character, it provides tanning-cum-filling action which in turn reduces the retanning agent consumption in subsequent processes. Scanning electron microscopic study, porosity analysis, and hand assessment results clearly indicate the significant improvement in organoleptic properties. In addition, the process also enjoys the benefits of zero chromium containing solid waste generation, 71.4% reduction in chromium input, and high chromium transfer efficiency (92%) than the conventional process (36%), and 74.4% reduction in total dissolved solids generation. Furthermore, the water consumption and chemical input are reduced by 51.6 and 17%, respectively. Reduction in wastewater treatment cost and a high economic value of chromium-free leather scraps leads to a cumulative gain of US$ 39.84 per ton of raw material processing. Overall, a potential and practical applicability for cleaner and sustainable tanning is well established.