Removal of dissolved metals by zero-valent iron (ZVI): kinetics, equilibria, processes and implications for stormwater runoff treatment

Water Res. 2005 Oct;39(17):4153-63. doi: 10.1016/j.watres.2005.07.040. Epub 2005 Sep 21.

Abstract

Infiltration of stormwater runoff contaminated with metals is often questionable in several cases due to its long-term potential to cause deterioration of groundwater quality. To ensure the quality of filtrate, a pre-treatment of contaminated runoff is required. This study investigates the processes of copper and zinc ion removal from stormwater runoff using zero-valent iron (ZVI, Fe0). Kinetic and equilibrium tests were performed with laboratory-prepared and in situ stormwater runoff samples collected from roof, street and highway catchments. Based on the results, a substantial portion of Cu2+ is reduced and transformed to insoluble forms of Cu0 and Cu2O. Unlike copper, the adsorption and co-precipitation associated with freshly precipitated iron oxides play important roles for the removal of Zn2+. Investigations under various water quality conditions demonstrated a relatively minor impact on Cu2+ uptake rates. However, the different conditions apparently altered the removal stoichiometry and phases of the copper deposits. The removal rates of Zn2+ increase with higher dissolved oxygen (DO), ionic strength (IS), temperature (T) and pH. Dissolved organic carbon (DOC) in runoff samples forms complexes with metals and Fe2+, thereby kinetically decreasing the metal uptake rates. Furthermore, depending on its composition, a larger molecular weight organic fraction was found to preferentially compete for the adsorption sites. The study demonstrates that ZVI is a promising medium for achieving comparable capacity to a commercial adsorbent like granular ferric hydroxide (GFH). Long-term performance of ZVI, however, may be limited and governed by the formation of non-conductive layers of iron and cuprous oxides.

MeSH terms

  • Hydrogen-Ion Concentration
  • Iron / chemistry*
  • Kinetics
  • Metals / isolation & purification*
  • Microscopy, Electron, Scanning
  • Osmolar Concentration
  • Temperature
  • Water Pollutants, Chemical*

Substances

  • Metals
  • Water Pollutants, Chemical
  • Iron