Kinetic and Mechanism Study of PFOS Removal by Microscale Zero-Valent Iron from Water
Meng Ji1, Christos Christodoulatos1, Qiantao Shi1
1Center for Environmental Systems, Department of Civil Environmental and Ocean Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
Environmental Science & Technology
|March 20, 2025
Summary
Microscale zero-valent iron (mZVI) effectively removes perfluorooctanesulfonic acid (PFOS) through hydrophobic interactions, outperforming activated carbon. The magnetic portion of mZVI is key to this enhanced PFOS removal.
Area of Science:
- Environmental Chemistry
- Materials Science
- Water Treatment
Background:
- Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants.
- Perfluorooctanesulfonic acid (PFOS) is a widely detected and concerning PFAS.
- Effective remediation strategies for PFOS are urgently needed.
Purpose of the Study:
- Compare the efficacy of microscale zero-valent iron (mZVI) and activated carbon (AC) for PFOS removal.
- Investigate the role of magnetic and nonmagnetic fractions of mZVI in PFOS adsorption.
- Elucidate the primary removal mechanisms of PFOS by mZVI.
Main Methods:
- Batch adsorption experiments comparing mZVI and AC.
- Analysis of PFOS concentration reduction over time.
- Investigation of mZVI fractions (magnetic vs. nonmagnetic, acid-washed).
- In situ Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR).
Main Results:
- mZVI demonstrated significantly higher areal adsorption capacity (21 mg/m²) than AC (0.813 mg/m²).
- mZVI reduced PFOS from 50 to 6 mg/L within 8 hours at neutral pH.
- Magnetic solids of mZVI showed superior removal capacity compared to iron oxides/hydroxides.
- Hydrophobic effect, not electrostatic attraction or covalent bonding, was identified as the primary removal mechanism.
Conclusions:
- mZVI is a highly effective adsorbent for PFOS, surpassing AC.
- The magnetic fraction of mZVI plays a crucial role in PFOS removal.
- Understanding the hydrophobic removal mechanism can guide the development of advanced mZVI materials for PFOS remediation.
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