Heated Blends of Phosphate Sludge: Thermal Transformation and Microstructure Characterization
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The mining industry faces many environmental challenges resulting from the huge amounts of waste generated by mines such as phosphate sludge. This waste deposited in the mine site is a potential source of pollution. The aim of this study was to valorize Tunisian phosphates sludge in ceramic manufacturing. To this end, the microstructure of heated blends was characterized using X-ray diffraction (XRD), inductively coupled plasma and atomic emission spectrometry (ICP-AES), scanning electron microscope (SEM), thermal analyses (DTA-TG) and dilatometry. Their ceramic properties: shrinkage, water absorption, density and compressive strength were followed as a function of heating temperature and kaolin content. The DTA curve shows an exothermic peak at 900 °C, which corresponds to the neoformation of the gehlenite phase. Moreover, fluor-apatite phase remains stable up to about 1100 °C. Based on their mineralogical and ceramic properties, heated blends of phosphate sludge may be a used in the ceramic industry. The addition of kaolin at different proportions with phosphate sludge improved the performance of samples sintered at 1100 °C and proved that the content of phosphate sludge in the mixture remained limited to 30% wt against 70% wt of kaolin.
KeywordsCeramic Phosphate Sludge Dilatometry Pollution Kaolin