Síntese de silicato de lítio a partir do rejeito da mineração de ferro e sua utilização para captura de CO2

Abstract

The sandy tailings rich in silica (ca. 80-90%) is a by-product generated in the iron ore beneficiation industry. In Brazil, it is estimated that there was a generation of 164 million tons of this tailings in 2019, still destined in dams. In this context, the present work sought to synthesize lithium silicate from the sandy tailings of iron mining and its use for CO2 capture. The IOT were impregnated with LiOH using different Li: Si molar ratios (1, 2.5 and 4), calcined at 850 °C for 3h. In the solid state reaction method, all materials were prepared from a Li:Si molar ratio of 4, the variables were evaluated: calcination time (3h, 5h and 12h), calcination temperature (850 °C and 900°C) for 5h and milling of IOT. The materials were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy coupled with energy dispersive spectroscopy (SEM/EDS), Raman Spectroscopy, Infrared Spectroscopy and Mossbauer Spectroscopy. The CO2 capture performance of the materials was evaluated by thermogravimetric analysis using a CO2 flow through dynamic and isothermal tests. After lithium modification of the tailings, all materials presented lithium silicate as the main phase, except using the impregnation method at a molar ratio of 1 and 2.5. Lithium silicate synthesis is dependent on the synthesis method, Li: Si molar ratio, calcination time, calcination temperature and grinding. The crushed IOT and modified with lithium by the state reaction method, and using a Li:Si molar ratio of 4:1, calcined at 850°C for 5h showed better CO2 capture performance of 16% w/w, while in the isothermal test it reached 22% w/w at 670 °C. It also showed excellent cyclic stability during the four.