Accelerated carbonation of high Ca content municipal solid waste incineration fly ash and impact on leaching of heavy metal

The accelerated carbonation of high Ca content Municipal Solid Waste Incineration (MSWI) fly ash was investigated with an L:S ratio of 0 25:1 to study the effect of accelerated carbonation on the leaching of critical heavy metals (As, Cd, Cu, Zn, Sb, Pb) in the fly ash. The results of XRD analysis showed after carbonation the peaks of Ca (OH)₂ and CaClOH disappeared, while the peaks of CaCO₃ became intense. After carbonation, the mineral phase of Pb was changed and Cu compound (CuTi_2.05S₄) was identified. The TG/DTA analysis showed the weight gain of the fly ash before 440°C reached 5.70%. Furthermore, the SEM-EDS analysis confirmed the occurrence of the reaction of Ca (OH)₂ (s) + CO₂ (g) → CaCO₃ (s). The TCLP test of carbonated fly ash revealed that the leaching concentration of the critical heavy metals, except Cd, decreased within the carbonation time of 2 h. When the carbonation time was longer than 50 h, the leaching concentration of critical heavy metals, except Pb were higher than that of un-carbonated fly ash.