High-purity vaterite CaCO3 recovery through wet carbonation of magnesium slag and leaching residue utilization in cement

This work turned industrial waste of magnesium slag (MS) into two value-added products, high-purity vaterite and supplementary cementitious materials, through "leaching-carbonation" method. The various parameters on the leaching rate of Ca2+ from MS by using NH4Cl solution were investigated. The spherical vaterite with high purity of 96.5 % and high surface area (27.89 m2/g) could be successfully produced through wet carbonation of leachate with addition of glycine as crystal modifiers. In addition, the leachate solid residue (LSR) obtained from leaching process of MS had a smaller size destruction and higher surface area in comparison to Portland cement, resulting in an accelerated hydration process. The amorphous silica gel in LSR had a high pozzolanic effect, which resulted in a higher compressive strength development and refined pore structure in comparison to control samples. This work provides a novel treatment and can realize the high value-added utilization of MS.