Stabilization of lead in an alkali-activated municipal solid waste incineration fly ash–Pyrophyllite-based system

Abstract

This work focuses on the stabilization and speciation of lead (Pb) in a composite solid produced from an alkali-activated municipal solid waste incineration fly ash (MSWIFA)–pyophyllite-based system. The solid product was synthesized after mixtures of raw materials (dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate solution) were cured at 105 °C for 24 h. The product could reduce the leaching of Pb and the Pb concentration in the leachate was 7.0 × 10−3 using the Japanese leaching test and 9.7 × 10−4 mg/L using toxicity characteristics leaching procedure method, which satisfied the respective test criteria and successfully stabilized Pb in this system. The solid product had a compressive strength of 2 MPa and consisted mainly of crystalline phases. Scanning electron microscopy with X-ray analysis and X-ray absorption fine structure suggested that Pb was present along with Al, Si, and O, and that the atomic environment around the Pb was similar to that of PbSiO3. These results suggest that the alkali-activated MSWIFA–pyrophyllite-based system could be used to stabilize Pb in MSWIFA.