Chromium immobilization in basic magnesium sulfate cement: Experimental and density functional theory studies

This study investigated the effects of different concentrations of Cr(III) on the properties of basic magnesium sulfate cement (BMSC). In addition, the hydration process of BMSC with different concentrations of Cr(III) was studied using isothermal calorimetry and in-situ pH monitoring. A combined experimental approach and density functional theory simulation was further employed to investigate the solidification mechanism of Cr(III) in BMSC. The results indicated that Cr(III) affected the hydration heat, pH value, compressive strength and setting time of BMSC, and the influence became more obvious with the increase of Cr(III) concentration. In addition, the solidification efficiency of Cr(III) in BMSC was up to 99.9%; the efficient solidification of Cr(III) in BMSC primarily operated through ion exchange interactions, as revealed by density functional theory simulation and phase analysis results. Furthermore, the BMSC matrix after being immersed in simulated acid rain solutions for 28 days had a compressive strength of over 45 MPa, showing remarkable resistance to acids.