An integrated pickling-bating technology for reducing ammonia-nitrogen and chloride pollution in leather manufacturing

Abstract

Currently, ammonia-nitrogen (NH3–N), chloride (Cl−) and chromium (Cr) pollution from leather manufacturing processes attracts much attention and limited the sustainable development of the leather industry. In this paper, conventional trypsin bating and high-salt pickling procedures were substituted by a salt-free pickling-bating system, using acidic protease L80A and salt-free pickling agent naphthalene sulfonic acid (NSA); a novel integrated technology comprising non-ammonia bating, salt-free pickling and high-exhausting chrome-tanning methods was established to reduce NH3–N, Cl− and Cr pollution. The results indicated that the properties of the leather produced by the established method were better than the conventional method. Furthermore, the established integrated salt-free pickling-bating technology resulted in the almost elimination of NH3–N and chloride pollution from waste effluent. The total Cr utilization ratio was increased to 95% from 80%, the total Cr discharge was reduced by 74%. Scale-up experiments further verified the acceptability of this novel technology in terms of physical and organoleptic properties of the resultant leather. It can be easy to predict that the effluent liquors with a little amount of NH3–N, chloride and chromium can be disposed of conveniently. We suppose that the established novel technology is an environment-friendly technology and a way forward in the development of the modern sustainable leather industry.