Effect of modified diatomaceous earth on the heavy metal volatilization characteristics of aged refuse co-combustion

Abstract

ABSTRACT This paper investigated the adsorption performance of natural and modified diatomaceous earth (DE) for six heavy metal species (Cu, Zn, Ni, Cd, Pb, Cr) during the co-combustion of aged refuse (AR) and municipal solid waste (MSW) in a lab-scale tubular furnace. The aim was to examine the effects of temperature, sorbents, and modification methods on heavy metals’ adsorption performance. The capture rates of calcined diatomaceous earth (CDE) were higher than those of DE, especially for Ni at 700°C, whose capture rate increased to 78.6%. Modified sorbents with NaOH or Na2CO3 significantly reduced the volatility of six heavy metals at 700°C, with the volatilization rates (VR) of Ni and Zn decreasing by at least 50%. Meanwhile, for Cu, Pb, and Zn, the fixation of heavy metals in the bottom ash increased with rising the sorbents mass. However, when the combustion temperature was equal to or above 800°C, the effects of modification on the VR of Cd, Pb, and Zn diminished, except for 10 wt% DE and CDE-10%NaOH. Using NaOH-modified DE at higher temperatures increased the VR of Ni, Pb, and Zn, particularly for Ni whose VR increased by 21.13%. This work contributes to understanding DE’s control mechanism of heavy metals and investigates new heavy metal control strategies during the co-combustion of MSW and AR.