Mechanisms of zinc incorporation in aluminosilicate crystalline structures and the leaching behaviour of product phases.
This study quantitatively evaluates a waste-to-resource strategy of blending zinc-laden sludge and clay material for low-cost ceramic products. Using ZnO as the simulated zinc-laden sludge to sinter with kaolinite, both zinc aluminate spinel (ZnAl₂O₄) and willemite (Zn₂SiO₄) phases were formed during the sintering process. To analyse the details of zinc incorporation reactions, γ-Al₂O₃and quartz were further used as precursors to observe ZnAl₂O₄and Zn₂SiO₄formations. By firing the ZnO mixtures and their corresponding precursors at 750-1350°C for 3 h, the efficiency of zinc transformation was determined through Rietveld refinement analyses of X-ray diffraction data. The results also show different incorporation behaviour for kaolinite and mullite precursors during the formation of ZnAl2O₄and Zn2SiO₄in the system. In addition, with a competitive formation between ZnAl₂O₄and Zn₂SiO₄, the ZnAl₂O₄spinel phase is predominant at temperatures higher than 1050°C. This study used a prolonged leaching test modified from the US Environmental Protection Agency's toxicity characteristic leaching procedure to evaluate ZnO, ZnAl₂O₄, and Zn₂SiO₄product phases. The zinc concentrations in ZnO and Zn₂SiO₄leachates were about two orders of magnitude higher than that of ZnAl₂O₄ leachate at the end of the experiment, indicating that ZnAl₂O₄formation is the preferred stabilization mechanism for incorporating zinc in ceramic products.
a Department of Civil Engineering , The University of Hong Kong , Pokfulam Road, Hong Kong , SAR People's Republic of China.
Yuanyuan
Y
Tang
a Department of Civil Engineering , The University of Hong Kong , Pokfulam Road, Hong Kong , SAR People's Republic of China.
Kaimin
K
Shih
D019342:Acetic Acid / Q000737:chemistry; D017607:Aluminum Compounds / Q000737:chemistry*; D002516:Ceramics; D003460:Crystallization; D017640:Silicates / Q000737:chemistry*; D018505:Waste Management / Q000379:methods; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
D017607:Aluminum Compounds; D017640:Silicates; D017967:Zinc Compounds; D015032:Zinc; D019342:Acetic Acid; C029500:zinc silicate
kaolin; sludge; stabilization; thermal treatment; zinc