Reactivity of Nanoscale Zero-Valent Iron in Unbuffered Systems: Effect of pH and Fe(II) Dissolution

Abstract : While most published studies used buffers to maintain the pH, there is limited knowledge regarding the reactivity of nanoscale 0-valent Fe (NZVI) in poorly buffered pH systems to date. Here, the effect of pH and Fe(II) dissoln. on the reactivity of NZVI was studied during the redn. of 4-nitrophenol (4-NP) in unbuffered pH systems. The redn. rate increased exponentially with respect to the NZVI concn., and the ratio of dissolved Fe(II)/initial NZVI was related proportionally to the initial pH values, suggesting that lower pH (6-7) with low NZVI loading may slow the 4-NP redn. through acceleration of the dissoln. of NZVI particles. Addnl. expts. using buffered pH systems confirmed that high pH values (8-9) can preserve the NZVI particles against dissoln., thereby enhancing the redn. kinetics of 4-NP. Redn. tests using ferrous ion in suspensions of magnetite and maghemite showed that surface-bound Fe(II) on oxide coatings can play an important role in enhancing 4-NP redn. by NZVI at pH 8. These unexpected results highlight the importance of pH and Fe(II) dissoln. when NZVI technol. is applied to poorly buffered systems, particularly at a low amt. of NZVI (i.e., \textless0.075 g/L).
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Submitted on : Friday, August 28, 2015 - 4:25:19 PM
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Sungjun Bae, Khalil Hanna. Reactivity of Nanoscale Zero-Valent Iron in Unbuffered Systems: Effect of pH and Fe(II) Dissolution. Environmental Science & Technology, American Chemical Society, 2015, 49 (17), pp.10536-10543. ⟨10.1021/acs.est.5b01298⟩. ⟨hal-01188220⟩

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