Minimization of Chromium Discharge in Leather Processing by using Methanesulfonic Acid: A Cleaner Pickling-masking-chrome Tanning System

Abstract

Chrome tanning is the most important and widely used tanningmethod in leather manufacture hitherto. However, chromiumdischarge may be a serious environmental concerned pollutantin leather processing, which originates from both chrometanning and post-tanning operations. In order to minimize theemissions of chromium from the whole leather processing, anovel leather processing method integrating high chromiumexhaustion and low chromium leaching-out based on theapplication of methanesulfonic acid (MSA) was designed andoptimized. The results indicated that, being superior to theconventional processes, the chrome tanning and retanningprocesses with MSA were conducted at a high beginning pH(5.0) smoothly and the total chromium utilization ratio wasincreased to 95.8% from 81.0% in the novel processes.Accordingly, the total Cr dosage was decreased by 26.7% around,the residual Cr concentrations in each chrome-containingwastewater was decreased by 44%-85%, varying with theoperations, and the total Cr discharge generated in the wholeleather processing was reduced by 83.8% around, from 2.737 kg/tsalted-wet hide to 0.443kg/t salted-wet hide before next chromeprecipitation treatment. The area yields, mechanical propertiesand organoleptic properties of the leather from the new methodwere comparable with that from conventional processes.