Weathering treatment coupled with nano-silica filling to promote the engineering property of municipal solid waste incinerator bottom ash

Abstract

A new approach including weathering treatment and nano-silica filling was employed to promote the engineering properties of municipal solid waste incinerator (MSWI) bottom ash. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) was used to characterize the mineralogical and morphological changes due to the treatment. Changes of chemical stability, compressive strength and heavy metal leaching of MSWI bottom ash were also explored. After the weathering treatment, the content of organic matter decreased from 2.70% to 1.07%, while the carbonates increased from 0.70% to 2.05%. The nano-silica treatment filled the intrinsic and neo-formed micropores and coated the surface of MSWI bottom ash. Due to this process, the chemical stability was promoted. The compressive strength increased from 4.83 to 5.32 MPa. The leaching of Cu, Zn, Pb, Cr and Cd sharply decreased from 250.05 to 89.97 mg L⁻¹, 1080.45 to 173.14 mg L⁻¹, 1.25 to 0.70 mg L⁻¹, 72.58 to 12.96 mg L⁻¹ and 0.94 to 0.30 mg L⁻¹, respectively. The results suggested that the weathering treatment coupled with nano-silica filling could greatly promote the engineering properties of MSWI bottom ash, which is beneficial with respect to the reuse of MSWI bottom ash as the building material.