Carbonation washing of waste incinerator air pollution control residues under wastewater reuse conditions

This study investigates a novel carbonation washing approach for treating waste incineration Air Pollution Control residues (APCr), aiming to divert them from landfilling, mitigate carbon emissions, and reduce water consumption. 23 laboratory-scale tests using a 1.5 L stirred reactor carbonated over 500 g of APCr, achieving a mean carbonation degree of 250 gCO 2 /kg. The results show significant reductions in heavy metal leaching, including Pb (99.9 %), Zn (76.0 %), Fe (66.8 %), and Cr (96.5 %), while Cl, Na, and K ions remained in the wastewater. However, additional treatments are needed for Sb, which was mobilized upon carbonation. Process intensification with ultra-fine CO 2 bubble sparging and temperature optimization achieved CO 2 absorption rates exceeding 90 %, with optimal temperatures between 333 K and 343 K. The calcite-to-vaterite ratio increases with temperature, reflecting the greater stability of calcite at higher temperatures. Under wastewater reuse conditions, CO 2 uptake remained high, and over 90 % water recovery efficiency was achieved. A new re-carbonation technique using NaOH before CO 2 bubbling is expected to yield nearly pure CaCO 3 and a recyclable brine. This study highlights the potential of carbonation washing as an efficient pre-treatment for APCr in lime-sorbent-based waste incineration plants. Complemented by solidification using a binder, this approach aligns with the stabilization/solidification paradigm of waste management, potentially enabling to transform these residues into secondary raw materials for civil engineering applications and reducing the environmental burden of the incineration sector. Further scaled up laboratory experiments will be conducted to explore the pilot-scale potential of the current technology. • A new APCr carbonation washing method is investigated. • Heavy metal leaching, including Pb, Zn, Fe and Cr is significantly reduced. • Over 90 % CO 2 absorption rate in continuous gas flow is achieved. • An average of 250 gCO 2 per kg APCr is mineralized, with further potential through CaCl 2 -rich supernatant re-carbonation using NaOH and CO 2 .