Low-Temperature Reacting Glass-Ceramic Matrices for Incorporating Zinc and Lead in Waste Incineration Residues
Dr Shih, Kaimin (Principal investigator)
MSWI Residues, Hazardous Metals, Glass-Ceramic, Quantitative XRD, Leaching Behavior
RGC General Research Fund (GRF)
HKU Project Code
General Research Fund (GRF)
1) The main project purpose is to develop an economical method to thermally incorporate Zn and Pb in MSWI residues, as a safer and more reliable alternative of current cementation methods. The key challenge is on promoting the formation of glass-ceramic matrices with the aluminates and aluminosilicates for hosting Zn and Pb. The metal reaction pathways will be clearly identified by X-ray diffraction and electron diffraction results. The evolutionary processes of different Zn and Pb hosting phases will be portrayed across different precursor compositions and treatment schemes. 2) Our very unique quantitative X-ray diffraction analysis skill (Rietveld refinement method using the fundamental parameter approach and amorphous content quantification through internal standards) will then report the quantities of Zn and Pb hosting phases in products through high resolution X-ray diffraction data. An amorphous content quantification protocol employing commonly available calcium fluoride and silicon carbide internal standards will be also conducted to assist in the development of a reliable quantification method for the amorphous content. 3) Crystalline characteristics (lattice parameters, cation distribution, crystal size, etc.) of Zn- and Pb-containing phases generated from thermally reacting with the precursors will be quantified by Rietveld refinement on X-ray diffraction data to evaluate the quality of metal stabilization. The influences of different metal oxide additives on the structures of Zn- and Pb-hosting phases will also be assessed by monitoring the responses of these crystalline characteristics to provide direct evidence of the changes in the metal coordination environment. 4) Metal stabilization effects will be investigated by leaching experiments to quantify the metal leachability and by surface-sensitive characterization tools, e.g. atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), to elucidate the metal leaching behavior on the surface. Our strong expertise in high resolution electron microscopy (SEM and TEM) will assist the characterizations of glass-ceramic microstructures and the identification of metal-hosting phase nanostructures, such as grain boundary features, to facilitate the development of a reliable metal incorporation strategy. 5) Based on the mechanistic understanding of Zn and Pb phase transformations initiated by reactive glass-ceramic matrix incorporation, techniques will be elaborated for fabricating desired nano- and micro-structural features for MSWI residue-containing products. Overall, the implementation of this project will facilitate the goal of safely and reliably stabilizing the hazardous metals in MSWI residues through a scientifically sound and economically feasible treatment strategy.