Abstract

The distribution of chrome in the wastewaters from chrome tanning and post tanning processes was investigated. The results indicate that the residual chrome in chrome tanning and rechroming wastewaters is the main origin of chrome in effluent. Meanwhile, a considerable amount of chrome is released from leather in almost all the post tanning processes, including washing, neutralizing, retanning with various retanning agents, dyeing, fatliquoring and acid fixation. As a result, more than 60% of the chrome added is discharged into wastewater. It is interesting that the shrinkage temperature of leather does not decrease along with the release of chrome. This fact demonstrates that the chromes that effectively react with collagen and produce tanning action have not been released during these processes. So a right strategy to reduce chrome discharge in leather processing is to develop technologies that can increase effective chrome-collagen interaction with reduced chrome offer.