Stabilization of heavy metals in ceramsite made with sewage sludge

In order to investigate stabilization of heavy metals in ceramsite made with sewage sludge as an additive, the configuration of heavy metals in ceramsite was analysed by XRD and while leaching tests were conducted to find out the effect of sintering temperature (850 °C, 900 °C, 950 °C, 1000 °C, 1100 °C, and 1200 °C), pH (1, 3, 5, 7, 9, and 12), and H2O2 concentration (0.5 mol L−1, 1 mol L−1, 1.5 mol L−1, 3 mol L−1, and 5 mol L−1) on stabilization of heavy metals (Cd, Cr, Cu, and Pb) in ceramsite. The results indicate that leaching contents of heavy metals do not change above 1000 °C and sintering temperature has a significant effect on stabilization of heavy metals in ceramsite; leaching contents of heavy metals decrease as pH increases and increase as H2O2 concentration increases. XRD analysis reveals that the heavy metals exist in steady forms, mainly Pb2O(CrO4), CdSiO3, and CuO at 1100 °C. It is therefore concluded that heavy metals are properly stabilized in ceramsite and cannot be easily released into the environment again to cause secondary pollution.