Activation of Persulfate by Nanosized Zero-Valent Iron (NZVI): Mechanisms and Transformation Products of NZVI

Abstract

The mechanisms involved in the activation of persulfate by nanosized zero-valent iron (NZVI) were elucidated and the NZVI transformation products identified. Two distinct reaction stages, in terms of the kinetics and radical formation mechanism, were found when phenol was oxidized by the persulfate/NZVI system. In the initial stage, lasting 10 min, Fe was consumed rapidly and sulfate radicals were produced through activation by aqueous Fe. The second stage was governed by Fe catalyzed activation in the presence of aqueous Fe and iron (oxyhydr)oxides in the NZVI shells. The second stage was 3 orders of magnitude slower than the initial stage. An electron balance showed that the sulfate radical yield per mole of persulfate was more than two times higher in the persulfate/NZVI system than in the persulfate/Fe system. Radicals were believed to be produced more efficiently in the persulfate/NZVI system because aqueous Fe was supplied slowly, preventing sulfate radicals being scavenged by excess aqueous Fe. In the second stage, the multilayered shell conducted electrons, and magnetite in the shell provided electrons for the activation of persulfate. Iron speciation analysis (including X-ray absorption spectroscopy) results indicated that a shrinking core/growing shell model explained NZVI transformation during the persulfate/NZVI process.

Activation of persulfate by manganese oxide-modified sludge-derived biochar to degrade Orange G in aqueous solution

“…The lower degradation efficiency in the latter stage of reaction suggests a declined PS activation efficiency, which could be attributed to the loss of Mn component and depletion of Fe 2+ species that was transformed into Fe 3+ [4,25]. Another work concludes that the transformation between Fe 2+ to Fe 3+ and Fe 3+ to Fe 2+ could slowly activate PS (Equation (5)) and would show a slow pollutant degradation stage after the quick degradation stage [26]. Moreover, as suggested in FTIR analysis, functional groups may also contribute to the PS activation reaction.…”

Hydrothermal Enhanced Nanoscale Zero-Valent Iron Activated Peroxydisulfate Oxidation of Chloramphenicol in Aqueous Solutions: Fe-Speciation Analysis and Modeling Optimization

“…There are a series of available methods for PS activation [25]. It is worth mentioning that nanoscale zero-valent iron (nZVI) activation has attracted increasing attention due to its combined effects of Fe 0 , Fe 2+ , Fe 3+ , FeOOH, and Fe3O4 [26]. Furthermore, nZVI has been verified to be capable for decomposing organic pollutants through the reaction with dissolved oxygen to generate • OH, O2 • , and HO2 • [27,28].…”

Comparative Study of the Oxidative Degradation of Different 4-Aminobenzene Sulfonamides in Aqueous Solution by Sulfite Activation in the Presence of Fe(0), Fe(II), Fe(III) or Fe(VI)

“…It was found that Fe(II)/sulfite system can achieve good oxidation of all SAs by means of FeSO3 + species (Reactions (5), (6), and (28)) ( Table S2, Exp. 39, 48, and 57), since Fe(II) could be easily oxidized to Fe(III) in the presence of O2 (Reaction (5) and (35)).…”

“…Fe 2+ → Fe 3+ + e - (35) On the other hand, in the presence of an excess of sulfite, the rapid formation of Fe(III) is followed by a slower redox process, during which Fe(II) oxidation is independent of its concentration [40]. SO3 •− radicals, which could be produced by Fe(II) and Fe(III) reaction with sulfite (Reactions (4)-(28)), should then raise the sulfonamide degradation.…”

“…The use of Fe(II)-Fe(III)/sulfite systems are, therefore, good candidates for their use in the detoxification of contaminated water [22][23][24][25][26][27][28][29][30]32,34]. Fe(0) represents an alternative as an activator in radicals generation [35], and the use of Fe(VI) and sulfite produces a synergic effect, speeding up the removal of contaminants [28]. The effectiveness of a degradation process in water treatment also implies that the degraded byproducts do not harm the environment.…”