Beneficial metal stabilization mechanisms using simulated sludge incineration ash for ceramic products

BACKGROUND This study explored the feasibility of a waste to resource strategy by using incineration ash of sewage/waste‐water treatment sludge as part of the raw materials for ceramic processing. Reactions between metal oxides (CuO, ZnO), common metal containing form in incineration ash, and kaolinite based ceramic raw materials (kaolinite, mullite) were observed. The metal incorporation behavior was determined using quantitative X‐ray diffraction analysis. RESULTS The optimal sintering temperature for copper incorporation was 1000°C, with CuAl2O4 phase dominating the system. For zinc incorporation, ZnAl2O4 and Zn2SiO4 formed in competition, with ZnAl2O4 found to predominate at temperatures higher than 1150°C. To determine the preferred phases for long‐term metal stability, a prolonged toxicity characteristic leaching procedure was carried out to quantify metal leaching performance and explore the leaching behavior. Metal leaching following incorporation in spinel leachates was significantly lower than those in oxide and silicate leachates, and the surface leaching behavior was also analyzed for the consideration of long‐term metal stability. CONCLUSION The overall results indicate that spinel formation is a preferred metal stabilization mechanism when incorporating sludge incineration ash into ceramic products and is also a key control step to safely implement this waste to resource strategy for a more sustainable engineering solution. © 2013 Society of Chemical Industry