Metals removal from thermally treated tannery sludge: A novel approach

Abstract

Tannery sludge contains significant amount of various metals. These metals containing tannery sludge management has become a great challenge for the survival of tanning industry. The aim of this work was to remove metals especially chromium (Cr) from the thermally treated tannery sludge with a possible way of decontaminating without any chemical treatment for safe disposal. Tannery sludge was thermally treated at 100 to 1000 °C with an interval of 100 °C for 4 h and metals removal was assessed through the Toxicity Characteristic Leaching Procedure (TCLP). The presence of metals in aqueous solution was quantified by Flame Atomic Absorption Spectrophotometer (FAAS). Results indicate that Cr removal from the thermally treated tannery sludge was minimum at low temperature (<400 °C) due to the presence of organic substance. The maximum Cr removal was found at 600 °C. In the case of zinc (Zn), nickel (Ni) and copper (Cu) the maximum removal was at low temperature (<400 °C) and decreased with increasing temperature. In addition, metals removal efficiency were changed with temperature variation except for lead (Pb). The 98% Cr could be removed from the thermally treated tannery sludge at 600 °C or all the metals studied could be immobilized at 1000 °C.