Pickle-free chrome tanning using a polymeric synthetic tanning agent for cleaner leather processing

Abstract

Stringent environmental regulations on the discharge of pollutants from various industries have prompted researchers to seek the development of eco-benign technologies. Conventional chrome tanning in leather processing discharges significant amounts of chromium, total dissolved solids and chlorides. Hence, tanners are looking for new product-process innovations towards low-waste and high exhaust chrome tanning. A polymeric syntan, which can enable pickle-free chrome tanning using commercial basic chromium sulphate, has been developed. A convenient process for tanning goatskins as well as cow hides has been designed. This method enhances the uptake of chromium to above 90%. Although the developed process is a highly reactive system, the tanned leathers are free from physical deposition of chromium as seen from microscopic analysis. The distribution of chromium in thicker cow sides is uniform and comparable to that of conventional tanned leathers even at reduced dosage. Further, the novel product-process helps to reduce the chemical oxygen demand (COD), total dissolved solids (TDS) and chlorides in the spent tan liquor by 50, 80 and 98% respectively. The product offers full, soft leathers having a shrinkage temperature comparable to that of conventional chrome tanned leathers. This integrated process provides reduction in chemicals, water, time and power consumption. Thus the novel product/process developed not only seeks advantages in reducing pollution loads but also seems to be techno-economically viable.