Kinetic and mechanistic aspects of selenite oxidation by chlorine, bromine, monochloramine, ozone, permanganate, and hydrogen peroxide

Liu, Shaogang; Salhi, Elisabeth; Huang, Wan-Ting; Diao, Kai-Sheng; Gunten, Urs von

doi:10.1016/j.watres.2019.114876

Cited by 17 publications

(20 citation statements)

References 50 publications

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“…The pseudo-first-order rate constants ( k obs,HOBr , eq ) for Tl(I) oxidation by HOBr T were determined to be 8.11 × 10 –3 to 1.21 × 10 –1 s –1 , which were about 14 (pH 7.5) to 497 (pH 5.5) times higher than those using HOCl as the oxidant . Similar differences in the kinetics of bromination and chlorination processes were also observed for Mn(II), Se(IV), As(III), , and various organic contaminants …”

Section: Resultsmentioning

confidence: 61%

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

Cheng

Huang

et al. 2021

Environ. Sci. Technol.

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The oxidation of thallium [Tl(I)] to Tl(III) by chlorine (HOCl) is an important process changing its removal performance in water treatment. However, the role of bromide (Br–), a common constituent in natural water, in the oxidation behavior of Tl(I) during chlorination remains unknown. Our results demonstrated that Br– was cycled and acted as a catalyst to enhance the kinetics of Tl(I) oxidation by HOCl over the pH range of 5.0–9.5. Different Tl(I) species (i.e., Tl+ and TlOH(aq)) and reactive bromine species (i.e., HOBr/BrO–, BrCl, Br2O, and BrOCl) were kinetically relevant to the enhanced oxidation of Tl(I). The oxidation by free bromine species became the dominant pathway even at a low Br– level of 50 μg/L for a chlorine dose of 2 mg of Cl2/L. It was found that the reactions of Tl+/BrCl, Tl+/BrOCl, and TlOH(aq)/HOBr dominated the kinetics of Tl(I) oxidation at pH < 6.0, pH 6.0–8.0, and pH > 8.0, respectively. The species-specific rate constants for Tl+ reacting with individual bromine species were determined and decreased in the order: BrCl > Br2 > BrOCl > Br2O > HOBr. Overall, the presented results refine our knowledge regarding the species-specific reactivity of TI(I) with bromine species and will be useful for further prediction of thallium mobility in chlorinated waters containing bromide.

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Section: Resultsmentioning

confidence: 61%

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

Cheng

Huang

et al. 2021

Environ. Sci. Technol.

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“…The second-order rates of As(III) reacted with HO • and permanganate are 8.5 × 10 8 M –1 s –1 and 2.8 × 10 6 M –1 s –1 , respectively. As(IV) disproportionation and As(III) oxidation by HO • and permanganate are spontaneous fast reactions. , Thus, the rate-limiting step of As(V) formation during the oxidation of roxarsone could be the reaction of HO • and roxarsone to generate As(IV).…”

Section: Results and Discussionmentioning

confidence: 97%

“…As(IV) disproportionation and As(III) oxidation by HO • and permanganate are spontaneous fast reactions. 40,42 Thus, the rate-limiting step of As(V) formation during the oxidation of roxarsone could be the reaction of HO • and roxarsone to generate As(IV).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Complete Removal of Organoarsenic by the UV/Permanganate Process via HO^• Oxidation and in Situ-Formed Manganese Dioxide Adsorption

et al. 2021

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The UV/permanganate process is an innovative advanced oxidation process (AOP) that generates oxidative species, such as hydroxyl radicals (HO • ) and reactive manganese species (RMnS), and adsorptive species of in situ formed MnO 2 . The cooperation of oxidation and adsorption has the potential to remove organic metals from water. Herein, the removal of organoarsenic compounds of roxarsone and p-arsanilic acid by UV/permanganate was investigated. The pseudo-first-order reaction rate (k ox ′) of roxarsone was 0.0375 min −1 at a permanganate dose of 100 μM and pH 7.0 in the UV/ permanganate process, which was mainly attributable to HO • . The transformation of roxarsone was initiated with a HO • attack on the C−As bond, releasing As(V), which was then removed from the aqueous phase by MnO 2 adsorption. Additionally, hydroxylated products were generated by HO • oxidation and subsequently oxidized into nitro-1,4-benzoquinone and ring cleavage products. Under neutral conditions, the removal rate of total arsenic reached 73% at 20 min, 50% of roxarsone was transferred to As(V) via oxidation, and the in situ formed MnO 2 could remove 78% of the remaining roxarsone and 70% of As(V) via adsorption. With an increase in the pH from 3.0 to 9.0, the k ox ′ of oxidation decreased by 68%, whereas the removal rate of total arsenic increased from just 20% to 73%. This is the first study to use the UV/permanganate process to completely remove organic heavy metals with the combination of oxidative and adsorptive species, which demonstrates that this process is promising in water treatment.

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“…These results indicate that the presence of Cl − and generated chlorine-based oxidants will greatly hinder SeDER in single-chamber electrochemical systems, potentially by initiating solution-phase oxidation of Se(IV) to Se(VI) and Se(-II) to Se(IV) (Figure 3B). 32,33 When treating wastewater containing high Cl − levels, we would recommend a two-chamber electrochemical system to separate anodic and cathodic reactions and prevent chlorine-based oxidants in the catholyte.…”

Section: = +mentioning

confidence: 99%

Competing Ion Behavior in Direct Electrochemical Selenite Reduction

Zou

Mauter

2021

ACS EST Eng.

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Anthropogenic selenium (Se) released in industrial and agricultural wastewaters presents toxicity challenges for local ecosystems. Se direct electrochemical reduction (SeDER) is an effective and thermodynamically favorable approach for Se(IV) removal, but evaluating the feasibility of SeDER in application requires a comprehensive understanding of system performance in complex water matrices. This study evaluates both the cathodic and anodic competing ion behavior in a SeDER process, including both four-and six-electron Se(IV) reduction pathways. The results suggest that sulfate promotes electrochemical Se(IV) removal efficiency by 11−23%, but nitrate hinders Se(IV) removal (2−11% decrease) by occupying cathodic reaction sites. The anodic competing ions, especially chloride, decrease SeDER performance by generating strong oxidants and disrupting Se(IV) reduction pathways. We also find that four-electron Se(IV) reduction outperforms its six-electron counterpart when treating simulated fluegas desulfurization wastewater (with 7 g L −1 Cl − ), with a lowest effluent Se level of 0.23 mg L −1 , a highest removal efficiency of 96.9%, and a threshold deposition capacity of 3.5 g m −2 in a 7-day semicontinuous operation. Electrochemical Se(IV) removal using our prototype batch reactor is not competitive for treating low-Se concentration agricultural wastewaters (up to 24% removal). The results suggest the need for future work to evaluate alternative electrodes and reactor design that reduce water splitting reactions, enhance Faradaic efficiency, and promote mass transfer to the electrode surface.

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Kinetic and mechanistic aspects of selenite oxidation by chlorine, bromine, monochloramine, ozone, permanganate, and hydrogen peroxide

Cited by 17 publications

References 50 publications

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

Complete Removal of Organoarsenic by the UV/Permanganate Process via HO^• Oxidation and in Situ-Formed Manganese Dioxide Adsorption

Competing Ion Behavior in Direct Electrochemical Selenite Reduction

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Kinetic and mechanistic aspects of selenite oxidation by chlorine, bromine, monochloramine, ozone, permanganate, and hydrogen peroxide

Cited by 17 publications

References 50 publications

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

Complete Removal of Organoarsenic by the UV/Permanganate Process via HO• Oxidation and in Situ-Formed Manganese Dioxide Adsorption

Competing Ion Behavior in Direct Electrochemical Selenite Reduction

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Complete Removal of Organoarsenic by the UV/Permanganate Process via HO^• Oxidation and in Situ-Formed Manganese Dioxide Adsorption