An Eco-Friendly Tanning by Aromatic Sulphonic Acids for Enhancing Chrome Absorption and Reducing the Negative Impact on Environment

Abstract

This study was carried out for reducing the environmental effects of chromium and sodium chloride resulting in leather tanning process through salt-free pickling, which is considered as the most important way in reducing pollution of sodium chloride in process of chrome tanning. Two aromatic sulphonic acids (naphthalene sulphonic acid and phenol sulphonic acid) were prepared by sulphonation reaction. Thirty sheep pelts were used in tanning process and divided into ten groups where each group contains three pelts. Group 1 was tanned by traditional method as a control group. While the other groups tanned with prepared aromatic sulphonic acids and sulphonic acid in concentrations (2, 3 and 4%) from bating weight. The results showed that salt free pickling acids have ability to reduce total dissolved solids (TDS), chloride content and chemical oxygen demand (COD) compared to traditional method. Also, results indicated that utilization of sulphonic acid with concentration (4%) enhanced chrome exhaustion from 79.62% to 90.10% and reduced Cr (III) in spent liquor from 6.63% to 2.83%. It had no bad influence on the quality of the finished leather as well and was suitable for using in leather manufacturing.