Techno Press

Advances in Environmental Research   Volume 1, Number 1, March 2012, pages 37-55
Reduction of perchlorate using zero-valent titanium (ZVT) anode: reaction mechanism
Chunwoo Lee, Bill Batchelor, Sung Hyuk Park, Dong Suk Han, Ahmed Abdel-Wahab and Timothy A. Kramer

Abstract     [Full Text]
    Here we show that perchlorate reduction during pitting corrosion of zero-valent titanium (ZVT) is likely caused by dissolved titanium species, especially Ti(II). Several possible mechanisms were suggested based on the literature and were evaluated based on experimental observations. Direct reduction of perchlorate on the bare metal of the ZVT electrode was thermodynamically infeasible due to the highanodic potential that was applied. Other potential mechanisms were considered such as reduction by small ZVT metal particles released from the electrode and direct reduction on the oxide layer of the electrode where potential was sufficiently reduced by a high anodic potential drop. However, these mechanisms were not supported by experimental results. The most likely mechanism for perchlorate reduction was that during pitting corrosion, in which ZVT is partially oxidized to form dissolved ions such as Ti(II), which diffuse from the electrode surface and react with perchlorate in solution. This mechanism is supported by measurements of the dissolution valence and the molar ratio of ZVT consumed to perchlorate reduced (ΔTi(0)/ΔClO4-). The results shown in this study demonstrate that ZVT undergoing pitting corrosion has the capability to chemically reduce perchlorate by producing dissolved Ti(II) and therefore, it has the potential to be applied in treatment systems. On the other hand, the results of this research imply that the application of ZVT undergoing pitting corrosion in treatment systems may not be feasible now due to several factors, including material and electricity costs and possible chloride oxidation.
Key Words
    perchlorate; reduction; corrosion; zero-valent titanium; reductant
Chunwoo Lee: Doosan Hydro Technology, Inc., Tampa, FL 33619, USA; Bill Batchelor: Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77840, USA;
Sung Hyuk Park: Environmental & Energy Research Team, GS Engineering & Construction Research Institute, Youngin-si, Kyunggi-do, 449-831, Republic of Korea;
Dong Suk Han and Ahmed Abdel-Wahab: Chemical Engineering Program, Texas A&M University at Qatar, Education City, Doha, PO Box 23874, Qatar;
Timothy A. Kramer: Deceased

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