Physical and Electrochemical Characterization of Aluminum Electrodes during Electrocoagulation

Chia Miang Khor, Michael Evan Liao, Arpita Iddya, Shengcun Ma, Fan Yang, Yu Hsuan Liu, Yousuf Z. Bootwala, Gyoung Gug Jang, Mark S. Goorsky, Eric M.V. Hoek, Costas Tsouris, Jim Mothersbaugh, Marta C. Hatzell, David Jassby

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Electrocoagulation (EC) of synthetic groundwater was conducted using a sacrificial aluminum electrode in a flow-through EC reactor with short retention times (<1 min) under varying hydrodynamic and electrochemical conditions. The treated water was allowed to settle for 24 h and achieved silicate removal of up to 50 ± 4%, and hardness removal of 11 ± 1%. Physical, chemical, and electrochemical characterization was performed to explore changes in electrode surface morphology and composition. Electrochemical impedance spectroscopy (EIS) showed that chemical reactions at the electrode/water interface are sensitive to changes in the immediate chemical environment. We demonstrate that the most energy-intensive step in EC is aluminum dissolution at the anode, which remained fairly constant due to the continuous renewal of the anode’s surface, a result of aluminum dissolution. At the cathode, a structural change in the oxide layer, from γ-Al2O3 to gibbsite, was detected by grazing-incidence X-ray diffraction, which decreased the resistance to charge transfer at the cathode surface, resulting in decreased electrode resistance. The high flow rate in the system minimized the accumulation of aluminum hydroxide solids and aluminum ions at the electrode/water interface, which minimized the formation of thick scalants and amorphous Al(OH)3 on the cathode and anode, respectively. It was further demonstrated by EIS that under these conditions the resistance to charge transfer was constant throughout the duration of the experiment.

Original languageEnglish
Pages (from-to)44-56
Number of pages13
JournalACS ES and T Water
Volume4
Issue number1
DOIs
StatePublished - Jan 12 2024

Funding

The funding for this project was generously provided by the National Alliance for Water Innovation (Award number 7550026).

FundersFunder number
National Alliance for Water Innovation7550026

    Keywords

    • corrosion
    • electrochemical characterization
    • electrocoagulation
    • hardness and silicate removal

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