Utilization of Sludge from Leather Tanning Residual Baths as Additive in Mortars

In tanneries, one of the environmental issues is the removal of trivalent Chromium from residual leather tanning floats. In this paper we have experimented separation of floats from leather tanning process and the precipitation of trivalent Chromium by flocculation with synthetic polymers. The method presents the following advantages: on one hand the trivalent Chromium can be extracted from sludge and re-use in tanning process; on the other hand, the sludge containing trivalent Chromium and synthetic polymers (polyacrylamide) can be used in the construction industry, as a binder with cement to obtain mortars. The freeze-thaw resistance of the mortar containing “polymer-sludge” addition, compared to the control subjected to 15-25 freeze-thaw cycles was greatly improved.