Effects of EDTA on the accelerated carbonation behavior of steel slag used as cementitious materials

To utilize the steel slag (SS) on a large scale and sequester CO2, a room-temperature wet carbonation process with the assistance of ethylene-diamine-tetra-acetic acid (EDTA) was developed. In this work, the accelerated carbonation process of SS with EDTA was investigated. The evolution of phase composition and microstructure of carbonated steel slag (CSS) was revealed by XRD, TG/DTG, FT-IR and SEM. The results show that the carbonation reaction can reduce the content of free calcium oxide in SS, and the volume stability of CSS-cement cementitious materials is greatly improved. The carbonation products are mainly fine calcite and the 28-day compressive strength of cementitious materials containing CSS is improved. EDTA accelerates the calcium leaching and has a catalytic effect on the carbonation reaction through chelating effect. SS with EDTA reached a CO2 sequestration rate of 14.3% after 60 min of carbonation. In addition, the cyclic performance of the continuous wet carbonation process was investigated. Although the CO2 sequestration efficiency of each cycle dropped, they were still higher than that of the control group, indicating the good potential for the continuous wet carbonation method through solvent recovery.