Effects of hydroxyapatite addition on heavy metal volatility during tannery sludge incineration.

The effectiveness of hydroxyapatite (HAP) on volatilization reducing of heavy metals during incineration of tannery sludge was investigated. The tannery sludge was treated through doped with different content of HAP, and then incinerated in the tube furnace at the temperature of 600 °C and 900 °C. The results showed that the volatilization rates decreased by 10.19% for Pb, 10.17% for Zn, 7.40% for Cu and 5.33% for Cr at 600 °C when the HAP content was raised to 20%. At 900 °C, the volatilization rates of Pb, Cr and Cu decreased by about 40.0%, 24.0% and 9.0%, respectively, while volatilization of Zn can be considered nearly unchanged at around 5%. The heavy metals can be stabilized effectively in the incineration after the pyromorphite-like minerals were formed in the sludge doped with HAP.