Atom-efficient route for converting incineration ashes into heavy metal sorbents

Area of Science:

• Materials Science
• Environmental Chemistry
• Waste Management

Background:

• Municipal solid-waste incineration bottom ashes possess unique properties like high alkalinity and metastable mineralogy suitable for sorbent synthesis.
• Existing methods for sorbent synthesis often involve costly and hazardous chemicals, creating a need for more sustainable alternatives.

Purpose of the Study:

• To investigate the atom-efficient conversion of municipal solid-waste incineration bottom ashes into valuable sorbent materials.
• To characterize the mineralogical and physical changes in bottom ashes after hydrothermal treatment.
• To evaluate the heavy metal adsorption performance of the synthesized sorbents.

Main Methods:

• Hydrothermal treatment of bottom ashes in rotary autoclaves under autogenic pH conditions.
• Characterization of mineral phases formed, specific surface area, and particle size.
• Adsorption experiments for Cd(2+), Zn(2+), and Pb(2+) at pH 5.

Main Results:

• Hydrothermal treatment successfully converted precursor mineral phases into zeolites and layered silicate hydrates, primarily katoite and sodium aluminum phosphate silicate hydrate.
• Specific surface area increased tenfold, and average particle size reduced twofold.
• The synthesized sorbents demonstrated significant adsorption capacities for Cd(2+), Zn(2+), and Pb(2+), comparable to conventional adsorbents.

Conclusions:

• Municipal solid-waste incineration bottom ashes can be efficiently converted into high-performance sorbents using a cost-effective and environmentally friendly hydrothermal method.
• The synthesized sorbents show promise for the removal of heavy metals from aqueous solutions.
• This approach offers a sustainable pathway for waste valorization and resource recovery.