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This dissertation, Glass-ceramic Matrices to Immobilize Actinide and Hazardous Metal Wastes by Changzhong, Liao, 廖长忠, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Glass-Ceramic Matrices to Immobilize Actinide and Hazardous Metal Wastes Submitted by LIAO CHANGZHONG (廖长忠) For the degree of Doctor of Philosophy at The University of Hong Kong in December 2015 The hypothesis in this study is to incorporate radionuclides/hazardous metals into a double- barrier container named glass-ceramic, in which radionuclides/hazardous metals were captured by a chemically stable and leach-resistant durable crystalline phase and the residual glass covers this crystalline phase as a second barrier. In this study, lanthanides (Ce, Nd, Gd, Yb) were used as surrogates for highly radioactive actinides (Np, Pu, Am and Cm). Hazardous metal wastes (red mud, cathode ray tube (CRT) funnel glass, chromite ore processing residue (COPR)) were immobilized in their corresponding glass-ceramic matrices and the potential reutilization of these glass-ceramic products were investigated. To avoid the significant signal interference between crystal and glass in the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) mode, it is for the first time to demonstrate the advantage of transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) mode to precisely determine the chemical composition of crystals especially nano-size crystals embedded in the glass. Two key conceptions, partitioning ratio and leaching ratio, were introduced to reveal the immobilization mechanisms of radionuclides/hazardous metals in the glass-ceramic products. Glass-ceramic with single zirconolite phase in the bulk sample was successfully synthesized in the SiO -Al O -CaO-TiO -ZrO -Na O-Ln-Oxide/UO (Ln=Ce, Nd, Gd, Yb) system. All the 2 2 3 2 2 2 3 samples experienced a phase transformation of cubic-zirconia to zirconolite when carried out heat-treatment. The size, morphology and quantities of the crystals in the above system can be controlled by adjusting temperature, dwell time and chemical ratio. The 100-500 nm zirconolite crystals crystalized at 1050 C for 2h from glass matrix was determined to be Ca Nd Zr Ti Al O . In this zirconolite crystal, heavy stacking faults were found and 0.83 0.25 0.85 1.95 0.11 7 3+ 3+ Nd ions prefer to occupy the CaO octahedron. The partitioning ratio of Nd in the zirconolite can be up to 41% but has a decrease when increasing crystallization temperature and has a decreasing linear relationship to the loading contents of Nd O . Increasing radius of 2 3 lanthanide ions leads to a decrease of partitioning ratio of ions in the zirconolite phase. The uranium-bearing crystalline phases in the glass-ceramic matrices maybe cubic-zirconia, zirconolite and CaUO . The phase compositions and transformation processes of sintered red mud were revealed. Formation of PbFe O was proved to be effective when sintering the mixture with 25 wt.% 12 19 CRT funnel glass and 75 wt.% red mud at a moderate sintering temperature (900 C). The leachable lead concentration from the sintered product is about three orders of magnitudes lower than that from the CRT funnel glass. In CaO-MgO-SiO -Al O -Cr O glass-ceramic 2 2 3 2 3 system, the formation of MgCr Al O spinel is highly related to the amount of Cr O . The x 2-x 4 2 3 partitioning ratio of Cr in the spinel phase was about 70% when adding 2 wt.% Cr O, and 2 3 increased to 90% with

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