Environmental applications of zerovalent metals: Iron vs. Zinc

The reactivity of particulate zero-valent metals in solution is affected by the metal type (e.g., Fe vs. Zn), particle size (nano vs. micro), surface conditions (passivation by coatings of oxides), and solution conditions (including the type and concentration of oxidants). Comparing the reactivity of various types of Fe⁰ and Zn⁰ with carbon tetrachloride (CCl₄) shows that the intended effect of properties engineered to give enhanced reactivity can be obscured by effects of environmental factors. In this case, rates of CCl₄ reduction by Zn⁰ are more strongly affected by solution chemistry than particle size or surface morphology. Under favorable conditions, however, Zn⁰ reduces CCl ₄ more rapidly-and more completely-than Fe⁰, regardless of particle size. The suitability of nano-sized Zn⁰ for environmental remediation applications is uncertain.