Solving the Antimony Paradox in Waste-to-Energy Bottom Ashes

We work at the intersection of metal recovery, pollutant stabilization, and CO2 mineralization to produce high-quality secondary raw materials (SCMs) from complex ashes, slags, and dusts.

While developing our separation process for incinerator bottom ash, we encountered a well-known but poorly understood issue:

The antimony paradox.

When CO2 mineralization is applied to ashes, it can unintentionally increase antimony release in water. A process intended to improve environmental performance may, under certain conditions, worsen leaching behavior.

Antimony is both a regulated pollutant and a critical raw material. Its mobility is therefore a technical, environmental, and economic bottleneck for circular applications in construction.

During density separation experiments, we identified singular yellow particles within specific fractions. Advanced characterization revealed a previously overlooked Pb–(Sn)–(Sb)–(As) oxide phase.

This phase appears to control both antimony and arsenic mobility.

Understanding this mechanism changes the approach.

Instead of just carbonating heterogeneous waste directly, we:

• recover metals first, high-density and magnetic,

• then perform mineral carbonation washing fraction under controlled conditions.

  
  

In many cases, the primary value is not the CO2 storage itself, but the improvement in material quality and pollutant stability. CO2 mineralization becomes part of a broader industrial optimization strategy.

Controlling trace-level chemistry is essential for meaningful circularity.

Stay tunned, the detailed scientific publication will be released in 2026.