Effect of crystal size on zinc stabilization in aluminum-rich ceramic matrix

Abstract

With aluminum as the predominant element, incineration residues from municipal solid waste and sewage sludge may be reused as precursors for zinc stabilization. As solid-state reactions are influenced by the crystal sizes of the reactants, the aluminum-containing components with different crystal sizes in the incineration residues may affect zinc transformation and immobilization. In this study, Al2O3 was prepared with a variety of crystal sizes to simulate the aluminum-rich incineration residue matrix, and ZnO was mixed with Al2O3 to study the zinc incorporation mechanisms. The crystal sizes of Al2O3 were determined using Rietveld refinement. Quantification results showed that ~ 30% of zinc was incorporated into the ZnAl2O4 spinel when Al2O3 with the largest crystal size was used. However, the zinc transformation was enhanced twofold when the Al2O3 precursor had the smallest crystal size. This study confirmed the potential enhancement of zinc immobilization by nanoscale crystals in simulated aluminum-rich incineration residues. By improving zinc stabilization efficiencies using poorly crystallized aluminum-containing compounds instead of increasing the energy consumption by increasing the sintering temperatures, we can achieve an economic and environmental win–win scenario for the beneficial utilization of incineration residues of municipal solid waste and sewage sludge.