Dynamic and static insights on the interaction mechanism between heavy metal contaminants in MSW incineration flue gas and modified carbon materials: Aggregation of PbO and CdO

Abstract

Clarifying the interaction mechanism between heavy metals and adsorbent is the foundation to trigger the efficiency upgrades of adsorption technology. However, the existing studies ignore the coupling effect between heavy metal pollutants, which leads to a mismatch between theory and practice. Ab-initio molecular dynamics and density functional theory calculations are combined to uncover the dynamical interactions of mixed Pb/Cd species over the transition metal-modified carbon materials (CMs), discovering a new mechanism for enhanced heavy metal removal. Among various mixtures, PbO/CdO generates a stable and compact quadrilateral structure, greatly favorable for the nucleation and agglomeration of gas-phase heavy metals. According to the bond length tracking and electronic analyses, PbO plays an aggregating role and CdO plays a stabilizing role, resulting in dynamic stabilization of the tetragonal aggregates. Due to the different charge transfer and hybridization strengths between the surface-active sites and aggregates, the aggregates can only be stably trapped by Fe-modified CM. In addition, the Fe-modified CM exhibits excellent aggregation properties in the wide temperature region and in the low molecular environment. Overall, Fe-modified CM achieves synergistic removal of PbO and CdO, accommodating the environment of wide temperatures and low heavy metal concentrations, which provides an inspiration for the adsorbent design.