Effects of municipal solid waste incineration fly ash on solidification/stabilization of Cd and Pb by magnesium potassium phosphate cement

Magnesium potassium phosphate cement (MKPC) is a novel agent for solidification/stabilization (S/S) of heavy metals. In this study, different ratios of municipal solid waste incineration fly ash (MSWI FA) were added to MKPC as an admixture to solidify/stabilize heavy metal in an attempt to reduce S/S cost while also disposing and reusing the MSWI FA. The effects of MSWI FA on different heavy metals, including Cd, Pb and a Cd-Pb mixture, were also investigated. The results showed that Cd leaching concentration increased gradually with increasing MSWI FA upon S/S of Cd or Cd-Pb mixtures, while Pb leaching concentration decreased, then increased for Pb and Cd-Pb mixtures. After curing for 90 d, the compressive strength of all MKPC pastes decreased gradually with increasing MSWI FA. Generally, a percentage of MSWI FA below 40% is suitable for being used as an admixture of MKPC to S/S heavy metals, and less than 20% is suggested for being used as a component of construction material. As an admixture of MKPC, MSWI FA exhibited an obviously synergistic effect on S/S of Pb, while it had a lesser effect on S/S of Cd, primarily because of its great adsorption characteristics and chemical fixation of Pb. (C) 2015 Elsevier Ltd. All rights reserved.