The effects of pH and addition of an organic buffer (HEPES) on nitrate transformation in Fe0-water systems

Lara L. Zawaideh, Tian C. Zhang

Research output: Contribution to journalConference articlepeer-review

80 Scopus citations


The feasibility of using zero-valent iron (Fe0) powder to remediate nitrate-contaminated water was studied using bench-scale batch reactors. Operational parameters, such as Fe0 dosage (w/v), initial concentration of nitrate-nitrogen, pH, and the use of an organic buffer (HEPES) were studied, specifically focusing on the effects of pH and the addition of HEPES on nitrate transformation using zero-valent iron-powder. Nitrate-nitrogen was removed by 94% when 0.01 M of HEPES was added to a non-shaking batch reactor containing 20 mg/l nitrate-nitrogen and 4% (w/v) of Fe0. Shaking was proved to be more efficient than no shaking. Using the response surface methodology it was found that nitrate removal was closely related to pH. At low pH (e.g., pH < 2), the nitrate removal was fast and efficient (95% to 100%). At high pH (e.g pH > 11), the transformation of nitrate was fast and efficient only for low concentration of nitrate in the Fe0H2O system. At normal pH range (pH = 6 to 8), nitrate removal was usually lower than 50% without buffer treatment. The addition of the organic buffer (HEPES) could greatly enhance the nitrate transformation in a wide pH range (e.g., pH = 2 to 11).

Original languageEnglish (US)
Pages (from-to)107-115
Number of pages9
JournalWater Science and Technology
Issue number7 pt 6
StatePublished - 1998
EventProceedings of the 1998 19th Biennial Conference of the International Association on Water Quality. Part 1 (of 9) - Vancouver, Can
Duration: Jun 21 1998Jun 26 1998


  • Buffer
  • Nitrates
  • Remediation
  • pH

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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