CO2 mineralization and heavy metal leaching of multi-source ashes from municipal solid waste incineration

Abstract

Mineralization holds great promise in simultaneously fixing CO2 and treating ash from the municipal solid waste incineration (MSWI). However, characteristics of CO2 mineralization and heavy metal leaching largely depends on the generation process of ashes. Herein, we report a systematic evaluation on the direct aqueous carbonation of multi-source MSWI ashes and leaching behavior of heavy metals before and after mineralization. Influencing factors for CO2 mineralization are determined to follow the order of CO2 concentration > temperature > solid–liquid ratio > stirring speed. Spray tower fly ash from the semi-dry process and bag filter fly ash from the dry process exhibit better sequestration capacities of 82.3 g-CO2/kg-ash and 150.9 g-CO2/kg-ash with a maximum CO2 removal rate of 0.117 mmol/s and 0.191 mmol/s among all ashes. Moreover, leaching concentration of Pb/Cu/As/Ni/Hg in six MSWI ashes all decreases significantly after CO2 mineralization. These findings could provide guidance for the potential intensive utilization of MSWI ashes in CO2 mitigation.