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Performance enhancement of zero valent iron based systems using depassivators: Optimization and kinetic mechanisms
Published in Elsevier Ltd
2016
PMID: 27395028
Volume: 102
   
Pages: 436 - 444
Abstract
The long-term ability of Zero-Valent Iron (ZVI) in contaminant removal relies on the effectiveness of iron to serve as electron donor, which makes it a versatile remediation material. However, the formation of oxide and hydroxide layers results in passive layer on ZVI surface during contaminant removal hinders its reactivity. The focus of this research was to evaluate the performance of corrosive agents such as acetic acid (HAc), aluminium sulphate (Alum) and potassium chloride (KCl) as depassivators to overcome passivation for sustainability and longevity. Batch experiments using seven combinations of the above chemicals were conducted to optimize the dosage of depassivators based on passive layer removal. The influence of depassivators in catalytic activity of ZVI in removing Cr 6+ was evaluated. The passive layer on ZVI particles was characterized using Scanning Electron Microscopy (SEM) and confirmed by Energy-Dispersive X-ray spectroscopy (EDAX) analysis. The major mechanisms in passive layer removal was found to be H + ion embrittlement followed by uniform depassivation when [HAc] was used and pitting corrosion when [Alum] and [KCl]were used. All the seven sets of chemicals enabled depassivation, but considering the criteria of maximum depassivation, catalytic activity and long term reactivity the depassivation treatments were effective in order as [HAc-Alum] > [HAc-Alum-KCl] >[HAc] > [Alum] > [HAc-KCl] > [KCl] > [Alum-KCl]. The kinetic rate of ZVI using [HAc-Alum] and [Alum] was relatively unchanged over the pH range of 4–10, made it suitable for ex-situ remediation. This insignificant influence of initial pH in catalytic activity of ZVI along with the improvement in longevity and sustainability makes it suitable for effective water treatment applications. The present work has successfully demonstrated that chemical depassivation can restore considerable reactivity of ZVI in the existing permeable reactive barriers. © 2016 Elsevier Ltd
About the journal
JournalData powered by TypesetWater Research
PublisherData powered by TypesetElsevier Ltd
ISSN00431354
Open AccessNo
Concepts (49)
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    Aluminum compounds
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    Aluminum corrosion
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    Catalyst activity
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    Chlorine compounds
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    Electrochemical electrodes
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    Energy dispersive spectroscopy
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    Hydrogen embrittlement
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    Impurities
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    Iron
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    pH
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    Pitting
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    POTASH
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    POTASSIUM CHLORIDE
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    Scanning electron microscopy
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    SULFUR COMPOUNDS
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    Sustainable development
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    DEPASSIVATION
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    Hexavalent chromium
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    Hydrogen ions
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    Life span
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    Zero-valent iron
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    CHEMICAL WATER TREATMENT
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    Acetic acid
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    Aluminum sulfate
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    Chromium
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    POTASSIUM CHLORIDE
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    Proton
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    Unclassified drug
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    ZERO VALENT IRON
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    Chemical process
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    Dissolution
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    Equipment
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    Hydrogen
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    Optimization
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    Performance assessment
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    Pollutant removal
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    Reaction kinetics
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    Water treatment
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    Article
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    Catalysis
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    Corrosion
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    Kinetics
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    Priority journal
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    ROENTGEN SPECTROSCOPY
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    Chemistry
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    Water management
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    Water pollutant
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    Water pollutants, chemical
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    Water purification