Why does dissolved oxygen govern Mn(III) formation and micro-pollutant abatement in the permanganate/bisulfite process?

Dong, Huiyu; Duan, Shule; Liu, Chao; Yuan, Xiangjuan; Qiang, Zhimin

doi:10.1016/j.cej.2019.123556

Cited by 13 publications

(2 citation statements)

References 62 publications

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“…However, direct reactivity of Mn(VII) with many TrOCs remains limited. Consequently, ongoing research has been investigating strategies for enhancing Mn(VII) reactivity with TrOCs via the addition of activators (such as bisulfite − and peroxymonosulfate , ) and redox mediators (such as quinone, 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS), 1-hydroxybenzotriazole (HBT), and 2,2,6,6-tetramethylpiperidine- N -oxyl (TEMPO)). The reaction of bisulfite with Mn(VII) has been shown to generate sulfate radical (SO 4 • – ), hydroxyl radical ( • OH), and manganese intermediates (i.e., Mn(III), Mn(V), and Mn(VI)) , that can be much more reactive with TrOCs than Mn(VII).…”

Section: Introductionmentioning

confidence: 99%

Abatement of Organic Contaminants by Mn(VII)/TEMPOs: Effects of TEMPOs Structure, Organic Contaminant Speciation, and Active Oxidizing Species

Zhang

Shi

Cui

et al. 2022

Environ. Sci. Technol.

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In this study, a representative redox mediator, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), and its para-substituted derivatives (TEMPOs: 4-hydroxyl-TEMPO, 4-acetylamino-TEMPO, and 4-amino-TEMPO) significantly accelerated the abatement of trace organic contaminants (TrOCs, i.e., bisphenol-A (BPA), phenol, amines, and phenylbutazone) by Mn(VII) over a wide pH range of 4.0–9.0. The addition of substituents at para to the > N–O• moiety significantly influenced the degradation kinetics of TrOCs by changing the reduction potentials of TEMPOs and the corresponding oxoammonium cations (TEMPOs+); a linear relationship was observed between the substituents’ para Hammett sigma constants and the reduction potentials of TEMPOs and TEMPOs+. Pseudo-first-order reaction rate constants (k obs, min–1) of TrOC degradation by Mn(VII)/TEMPOs were also affected by the pK a of the TrOCs. Generally, the highest k obs values for individual TrOCs were observed at pH near the pK a even for TEMPOs+ with relatively pH-invariant reduction potentials. Overall, TrOC abatement kinetics were related to a combination of reactive species (Mn(VII), in situ formed MnO2, and TEMPOs+). For BPA, the relative contributions (R) of reactive species ranked as R(TEMPOs+) > R(Mn(VII)) > R(in situ formed MnO2) at pH 4.0–8.0, whereas R(Mn(VII)) > R(TEMPOs+) at pH 9.0 mainly owing to a change in BPA speciation as the pH approached the pK a1 value for BPA. The results of this study are useful for the development of heterogeneous TEMPO-based redox mediators and future applications of TEMPO-mediated oxidation systems for accelerated abatement of TrOCs in water.

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Section: Introductionmentioning

confidence: 99%

Abatement of Organic Contaminants by Mn(VII)/TEMPOs: Effects of TEMPOs Structure, Organic Contaminant Speciation, and Active Oxidizing Species

Zhang

Shi

Cui

et al. 2022

Environ. Sci. Technol.

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“…However, compared with ozone, Fenton, and other advanced oxidation processes, the reaction rates of some TrOCs with Mn(VII) are relatively low. , Therefore, studies on the strategies for enhancing Mn(VII) oxidation toward TrOCs were reported, such as the combinations of Mn(VII) with bisulfite, − peroxymonosulfate, , ozone, ultrasound, , ultraviolet irradiation, humic acid, and redox mediators. Particularly, redox mediators, such as quinone, hydroquinone, 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS), and 1-hydroxybenzotriazole (HBT), are becoming attractive due to the fact that they contain phenolic, quinone, or amine moieties identified in the ubiquitous natural dissolved organic matters (DOM).…”

Section: Introductionmentioning

confidence: 99%

Role of TEMPO in Enhancing Permanganate Oxidation toward Organic Contaminants

Zhang

Shi

Bai

et al. 2021

Environ. Sci. Technol.

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Permanganate (Mn(VII)) has been widely applied as an oxidant in water treatment plants. However, compared with ozone, Fenton, and other advanced oxidation processes, the reaction rates of some trace organic contaminants (TrOCs) with Mn(VII) are relatively low. Therefore, further studies on the strategies for enhancing the oxidation of organic contaminants by Mn(VII) are valuable. In this work, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), as an electron shuttle, enhanced Mn(VII) oxidation toward various TrOCs (i.e., bisphenol A (BPA), phenol, estrone, sulfisoxazole, etc.). TEMPO sped up the oxidative kinetics of BPA by Mn(VII) greatly, and this enhancement was observed at a wide pH range of 4.0−11.0. The exact mechanism of TEMPO in Mn(VII) oxidation was described briefly as follows: (i) TEMPO was oxidized by Mn(VII) to its oxoammonium cation (TEMPO + ) by electron transfer, which was the reactive species responsible for the accelerated degradation of TrOCs and (ii) TEMPO + could decompose TrOCs rapidly with itself back to TEMPO or TEMPOH (TEMPO hydroxylamine). To further illustrate the interaction between TEMPO and target TrOCs, we explored the transformation pathways of BPA in Mn(VII)/ TEMPO oxidation. Compared to Mn(VII) alone, adding TEMPO into the Mn(VII) solution significantly suppressed BPA's selfcoupling and promoted hydroxylation, ring-opening, and decarboxylation. Moreover, the Mn(VII)/TEMPO system was promising for the abatement of TrOCs in real waters for humic acid, and ubiquitous cations/anions had no adverse or even beneficial impact on the Mn(VII)/TEMPO system.

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Is Mn(III) a principal oxidant for trace organic contaminant abatement in permanganate/bisulfate process?

Duan

Dong

Hou

et al. 2022

Chemical Engineering Journal

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Why does dissolved oxygen govern Mn(III) formation and micro-pollutant abatement in the permanganate/bisulfite process?

Cited by 13 publications

References 62 publications

Abatement of Organic Contaminants by Mn(VII)/TEMPOs: Effects of TEMPOs Structure, Organic Contaminant Speciation, and Active Oxidizing Species

Abatement of Organic Contaminants by Mn(VII)/TEMPOs: Effects of TEMPOs Structure, Organic Contaminant Speciation, and Active Oxidizing Species

Role of TEMPO in Enhancing Permanganate Oxidation toward Organic Contaminants

Is Mn(III) a principal oxidant for trace organic contaminant abatement in permanganate/bisulfate process?

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