Abstract

Lignosulfonate (LGS) is a major by-product of pulping industry, generated in a huge amount each year. In this research, LGS was used as a reducing agent to reduce Cr(IV) to Cr(III) so that the LGS reduced chrome tanning agent (Cr-LGS) was prepared. It was found that the optimal mass ratio of LGS, dichromate and concentrated sulphuric acid was 0.7:1.0:1.0 for the preparation reaction. The LGS was degraded during the reaction while some functional groups, such as carboxyl, were derived. These structural changes in LGS made the Cr-LGS exhibit a satisfactory self-masking effect and thus possess good alkali resistance. Tanning experiments indicated that Cr-LGS achieved a high shrinkage temperature for wet-blue (Ts=118°C, Cr2O3 offer=1.5%). Compared with the leather tanned by commercial chrome tanning agent, the Cr-LGS tanned leather exhibited greater tensile and tear strengths with improved fullness and tightness.