Heated Blends of Phosphate Sludge: Thermal Transformation and Microstructure Characterization
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