Carbonation behavior of solidified/stabilized cadmium in phosphogypsum slag-based cementitious materials

To explore the enduring durability of the solidified matrix comprising phosphogypsum slag-based cementitious material (PSC) in a carbonization environment, the carbonization behavior of cadmium (Cd) solidified within an accelerated carbonization environment was examined. The carbonation depth, mechanical strength, and Cd leaching properties of PSC matrices doped with varying Cd2+ concentrations (ranging from 0 % to 1 % by weight) are analyzed. The impact of carbonation on Cd stabilization in the PSC matrix is examined using techniques including XRD, TGA, FTIR, XPS NMR, MIP, and SEM-EDS. The findings indicate a decrease in strength of PSC after carbonation; however, matrices containing Cd exhibit lower strength loss compared to those without heavy metals. The concentration of leached Cd2+ from the matrices increases from 0.134 μg/L to 4.4274 μg/L, but remains below the safety limits. During the crystallization process, Cd2+ are stabilized by ettringite (AFt) and calcium silicate hydrate (C-S-H) through the ion exchange with Ca2+, contributing to the strength and stability of the matrix under carbonation conditions. •Phosphogypsum slag-based cementitious materials (PSC) maintain favorable strength and leaching characteristics for solidified Cd after carbonization.•After carbonization, the PSC effectively stabilizes Cd as Cd(OH)2 and Cd(CO3)2.•Ion exchange between Cd2+ and Ca2+ preserves AFt and C-S-H, preventing decalcification.