Effects of Microwave-Assisted Thermal Treatment on the Fate of Heavy Metals in Municipal Solid Waste Incineration Fly Ash

Abstract

In recent years, many researchers have devoted themselves to the employment of microwave heating for immobilizing municipal solid waste incineration (MSWI) fly ash; however, they only focused on the leaching properties of heavy metals in treated fly ash. Herein, the aim of this study is to systematically investigate the effects of microwave-assisted thermal treatment on the fate of selected elements with conventional thermal treatment as control. The results showed that leaching behaviors of Pb, Cu, and Zn were successfully suppressed, while the leaching concentration of Cr was increased due to the transformation of Cr(III) to Cr(VI) after thermal treatment. Compared with conventional thermal treatment, microwave heating was more efficient for stabilizing MSWI fly ash. Sequential extraction experiment indicated that water-soluble and exchangeable fractions of Pb significantly declined with enhancement of the residual fraction, which manifested that Pb existed in more stable speciation. With regard to Cr, ...