Immobilisation of heavy metals in hazardous waste incineration residue using SiO2–Al2O3–Fe2O3–CaO glass-ceramic

Hazardous waste incineration residue (HWIR) is categorised as hazardous waste due to the presence of heavy metals such as Zn, Cu, and Cr. Based on the abundant components of silica, aluminium oxide, iron oxide, and calcium oxide in a HWIR from an environmental protection corporation in China, a 100% HWIR was used to prepare SiO2–Al2O3–Fe2O3–CaO glass-ceramic samples. The results showed that Zn, Cu, and Cr present in the glass-ceramic samples were effectively immobilised through the melting–sintering process. Among the four parameters of heat treatment, crystallisation temperature played the most significant role. The glass-ceramic that was formed under optimal conditions contained haematite, pseudobrookite, and anorthite, and exhibited a superior compressive strength, volume density, and water absorption of 204.84 MPa, 2.80 g/cm3, and 1.20%, respectively. Compared with the raw HWIR sample, the leaching concentrations of Zn, Cu, and Cr from the prepared glass-ceramic samples decreased significantly, and their immobilisation efficiencies exceeded 99%. Physical encapsulation in the glass-ceramic samples along with ion exchange in the amorphous glassy matrix and iron-rich crystalline phases were the main immobilisation mechanisms of Zn, Cu, and Cr.