Steam washing for MSWI-FA treatment

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Municipal solid waste incineration fly ash (MSWI-FA) poses environmental risks due to heavy metal content.
• Effective treatment is crucial for the safe stabilization and potential valorization of MSWI-FA in cementitious materials.

Purpose of the Study:

• To evaluate steam washing (SW) as an advanced pretreatment for MSWI-FA dechlorination.
• To assess the impact of SW on pollutant leaching and the physicochemical properties of MSWI-FA.

Main Methods:

• Utilized advanced analytical techniques including X-ray powder diffraction (XRPD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), isotope ratio mass spectrometry (IRMS), and scanning electron microscopy (SEM).
• Employed geochemical modeling to analyze pollutant leaching and ash characteristics.
• Investigated treatment effectiveness based on exposure time and liquid-to-solid ratio.

Main Results:

• SW removed up to 70% cadmium, 17% zinc, and 10% lead by dissolving soluble and carbonate/hydroxide fractions.
• Significant reductions in chloride (85%), sulfate (50%), and heavy metal (90%) leaching were observed, outperforming conventional water washing.
• Antimony leaching persisted above regulatory limits, linked to soluble Ca-antimonate phases.

Conclusions:

• Steam washing is a promising pretreatment for reducing hazardous leachate from MSWI-FA, improving its suitability for cementitious applications.
• Further research on antimony removal and life-cycle assessment is needed for sustainable MSWI-FA valorization.
• Optimized SW offers a potential sustainable strategy for MSWI-FA treatment.