Evaluation of MgO-rich materials obtained from Ferronickel slag for CO2 sequestration

Abstract

Because it has a high magnesium content, ferronickel (FeNi) slag is a potential alternative material for CO2 sequestration. The slag can be pretreated by alkali fusion with NaOH to obtain MgO-rich materials. In this study, the potential of this MgO-rich material for CO2 sequestration was investigated using MgO from FeNi slag (MgO-FS) and MgNa2SiO4 from FeNi slag (MNA). A MgO reagent (MgO-R) and FeNi slag were used as reference materials. The carbonation process was carried out using a batch autoclave with various liquid-to-solid (L/S) ratios, initial pressures, times, and CO2 concentrations. The MgO-FS effectively captured CO2 and had a carbonation performance comparable to that of MgO-R. The degrees of carbonation for MgO-R, MgO-FS, and MNA were 68.43 %, 65.53 %, and 39.40 %, respectively, when carbonation was carried out at 423 K and 8 bar with an L/S ratio of 10 mL/g and pure CO2 for 9 h. Combination of the FeNi slag alkali fusion process (1:2 FeNi slag/NaOH mass ratio, 773 K, and 4 h) with water washing and carbonation (4 bar, 423 K, 10 mL/g L/S ratio, 3 h, and pure CO2) gave a CO2 uptake efficiency of 0.119 ± 0.004 g CO2/g FeNi slag. The results of the degree of carbonation (i.e. 65.53 %), X-Ray diffraction spectra (magnesite mineral peak), and scanning electron microscope observations (magnesite crystal appearance) provide evidence that MgO-FS is an effective alternative material for indirect CO2 sequestration.