What is chelation, and how is it used in removing heavy metal pollution?

• A. Chelation oxidizes metals to a higher oxidation state
• B. Chelation binds metal ions with organic ligands to form stable complexes
• C. Chelation precipitates metals as sulfides
• D. Chelation involves evaporating metals

Answer: (B)

Chelation is the process where a molecule with several binding sites, called a ligand, grips a metal ion at multiple points to form a stable, ring‑like complex. This binding changes how the metal behaves, often making it more soluble and less reactive. In environmental cleanup, chelating agents such as EDTA or similar ligands attach to heavy metal ions in polluted water or soil, creating stable metal–ligand complexes. Because the metals are held tightly in these complexes, they can be removed from the contaminated media—by washing, pumping, or capturing the complexes in treatment systems—or immobilized in a controlled way to reduce bioavailability. This approach is different from oxidation or precipitation as sulfides and doesn’t rely on changing the metal’s oxidation state or forcing it to precipitate as a solid. But it requires careful management to prevent the soluble chelate from carrying metals to new locations before capture.