Phase analysis and thermo‐structural evolution of spent bleaching earth

Abstract This work investigated the phase composition and structural properties of spent bleaching earth, a harmful waste material used for filtering edible oil. The phase composition and structural properties were investigated through heat treatment from room temperature to 1000°C, using X‐ray diffraction with Rietveld refinement. The findings revealed that spent bleaching earth contains montmorillonite, β‐tridymite, β‐cristobalite, α‐quartz and aluminosilicates. Also, it was determined that the oil remnant from the industrial process is strongly adhered to the amorphous silica and plays a critical role during the phases' recrystallization. Results show a complex phase evolution as the calcination temperature increases. Montmorillonite partially decomposes above 900°C into aluminosilicates and tridymite transforms to cristobalite. Furthermore, aluminosilicates of the type Al 2 SiO 5 are promoted when the temperature is higher than 1000°C. This behavior is explained by the interactions between organic and inorganic components. The structural changes endow the spent bleaching earth with new and interesting properties, making it a promising candidate for the building industry.