Estabilização/solidificação de rejeito de mineração de ferro com ligante álcali-ativado oriundo de resíduos agroindustriais

Abstract

Due to the environmental and socioeconomic impacts associated with the disposal of mining tailings, the waste valorization and the use of alkali-activated binders are important for sustainable practices. Despite the existence of studies on alkaline activation applied to the stabilization of iron ore tailings (IOT), it is still necessary to explore the factors that influence the behavior of cemented waste. Furthermore, understanding the mechanical and leaching behavior of mining tailings with alkaline cements over time is crucial for the technical viability of the material. In this sense, this study evaluated the stabilization/solidification of IOT with alkali-activated binder (AAB) based on sugarcane bagasse ash and eggshell lime. Unconfined compressive strength (UCS), leaching, chemical and mineralogical composition and microstructure tests were conducted with 7 to 365 days and tensile strength and initial stiffness for shorter curing times. UCS of up to 6.59 MPa was achieved after 28 days of curing at 40°C. Reducing porosity and increasing binder content improved the strength and stiffness of IOT-AAB. UCS development occurred up to 60 days, showing low variation after this period. IOT-AAB with higher binder content and dry unit weight showed no metal toxicity over time. Ba, Mn, Pb and Zn were encapsulated in the cemented matrix and after 90 days of curing time, total encapsulation of metals was observed. The mineralogy of the cemented tailings showed no changes due to the leaching test. The presence of N-A-S-H gel was identified in all IOT-AAB mixtures. Exposure to the acidic environment of the leaching test altered the carbonate bond bands in IOT-AAB.