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Fenton's reagent is a solution of hydrogen peroxide (H₂O₂) and an iron catalyst (typically iron(II) sulfate, FeSO₄).^[1] It is used to oxidize contaminants or waste water as part of an advanced oxidation process. Fenton's reagent can be used to destroy organic compounds such as trichloroethylene and tetrachloroethylene (perchloroethylene). It was developed in the 1890s by Henry John Horstman Fenton as an analytical reagent.^[2]^[3]^[4]

Reactions

Iron(II) is oxidized by hydrogen peroxide to iron(III), forming a hydroxyl radical and a hydroxide ion in the process. Iron(III) is then reduced back to iron(II) by another molecule of hydrogen peroxide, forming a hydroperoxyl radical and a proton. The net effect is a disproportionation of hydrogen peroxide to create two different oxygen-radical species, with water (H⁺ + OH⁻) as a byproduct.^[5]

Fe²⁺ + H₂O₂ → Fe³⁺ + HO^• + OH⁻

(1)

Fe³⁺ + H₂O₂ → Fe²⁺ + HOO^• + H⁺

(2)

2 H₂O₂ → HO^• + HOO^• + H₂O

(net reaction: 1+2)

The free radicals generated by this process engage in secondary reactions. For example, the hydroxyl is a powerful, non-selective oxidant.^[6] Oxidation of an organic compound by Fenton's reagent is rapid and exothermic and results in the oxidation of contaminants to primarily carbon dioxide and water.

Reaction (1) was suggested by Haber and Weiss in the 1930s as part of what would become the Haber–Weiss reaction.^[7]

Iron(II) sulfate is typically used as the iron catalyst. The exact mechanisms of the redox cycle are uncertain, and non-OH^• oxidizing mechanisms of organic compounds have also been suggested.^{[citation needed]} Therefore, it may be appropriate to broadly discuss Fenton chemistry rather than a specific Fenton reaction.

In the electro-Fenton process, hydrogen peroxide is produced in situ from the electrochemical reduction of oxygen.^[8]

Fenton's reagent is also used in organic synthesis for the hydroxylation of arenes in a radical substitution reaction such as the classical conversion of benzene into phenol.

C₆H₆ + FeSO₄ + H₂O₂ → C₆H₅OH + (byproducts)

(3)

An example hydroxylation reaction involves the oxidation of barbituric acid to alloxane.^[9] Another application of the reagent in organic synthesis is in coupling reactions of alkanes. As an example tert-butanol is dimerized with Fenton's reagent and sulfuric acid to 2,5-dimethyl-2,5-hexanediol.^[10] Fenton's reagent is also widely used in the field of environmental science for water purification and soil remediation. Various hazardous wastewater were reported to be effectively degraded through Fenton's reagent.^[11]

Effect of pH on formation of free radicals

pH affects the reaction rate due to a variety of reasons. At a low pH, complexation of Fe²⁺ also occurs, leading to lower availability of Fe²⁺ to form reactive oxidative species (OH^•).^[12] Lower pH also results in the scavenging of ^•OH by excess H⁺,^[13] hence reducing its reaction rate. Whereas at high pH, the reaction slows down due to precipitation of Fe(OH)₃, lowering the concentration of the Fe³⁺ species in solution.^[11] Solubility of iron species is directly governed by the solution's pH. Fe³⁺ is about 100 times less soluble than Fe²⁺ in natural water at near-neutral pH, the ferric ion concentration is the limiting factor for the reaction rate. Under high pH conditions, the stability of the H₂O₂ is also affected, resulting in its self-decomposition.^[14] Higher pH also decreased the redox potential of ^•OH thereby reducing its effectiveness.^[15] pH plays a crucial role in the formation of free radicals and hence the reaction performance. Thus ongoing research has been done to optimize pH and amongst other parameters for greater reaction rates.^[16]

Impacts of operation pH on reaction rate
Low pH	Formation of [Fe(H₂O)₆]²⁺ complex, hence reducing Fe²⁺ for radical generation
Low pH	Scavenging of ^•OH by excess H⁺
High pH	Lower redox potential of ^•OH
	Self-decomposition of H₂O₂ due to decreased stability at high pH
	Precipitation of Fe(OH)₃ species in solution

Biomedical implications

The Fenton reaction has different implications in biology because it involves the formation of free radicals by chemical species naturally present in the cell under in vivo conditions.^[17] Transition-metal ions such as iron and copper can donate or accept free electrons via intracellular reactions and so contribute to the formation, or at the contrary to the scavenging, of free radicals. Superoxide ions and transition metals act in a synergistic way in the appearance of free radical damages.^[18] Therefore, although the clinical significance is still unclear, it is one of the viable reasons to avoid iron supplementation in patients with active infections, whereas other reasons include iron-mediated infections.^[19]

Applications

Fenton's reagent is used as a sewage treatment agent.^[20]

Fenton's reagent can be used in different chemical processes that supply hydroxyl ion or oxidize certain compounds:^{[citation needed]}

The first stage of Fenton's reaction (oxidation of Fe³⁺ with hydrogen peroxide) is used in Haber–Weiss reaction
Fenton's reagent can be used in organic synthesis reactions: e.g. hydroxylation of arenes via a free radical substitution
Conversion of benzene into phenol by using Fenton's reagent
Oxidation of barbituric acid into alloxan.
Coupling reactions of alkanes

Fenton-like reagent

Mixtures of Fe²⁺ and H₂O₂ are called Fenton reagent. If Fe²⁺ is replaced by Fe³⁺, it is called Fenton-like reagent.

Numerous transition metal ions and their complexes in their lower oxidation states (L_mMⁿ⁺) were found to have the oxidative features of the Fenton reagent, and, therefore, the mixtures of these metal compounds with H₂O₂ were named "Fenton-like" reagents.^[21]

References

^ Hemond, Harold (2015). Chemical Fate and Transport in the Environment (3rd ed.). Elsevier. p. 287. ISBN 9780123982568.
^ Koppenol, W. H. (1 December 1993). "The centennial of the Fenton reaction". Free Radical Biology and Medicine. 15 (6): 645–651. doi:10.1016/0891-5849(93)90168-t. PMID 8138191.
^ Fenton, H. J. H. (1894). "Oxidation of tartaric acid in presence of iron". Journal of the Chemical Society, Transactions. 65 (65): 899–911. doi:10.1039/ct8946500899.
^ Hayyan, M.; Hashim, M. A.; Al Nashef, I. M. (2016). "Superoxide ion: Generation and chemical implications". Chemical Reviews. 116 (5): 3029–3085. doi:10.1021/acs.chemrev.5b00407. PMID 26875845.
^ Tang, Zhongmin; Zhao, Peiran; Wang, Han; Liu, Yanyan; Bu, Wenbo (2021). "Biomedicine Meets Fenton Chemistry". Chemical Reviews. 121 (4): 1981–2019. doi:10.1021/acs.chemrev.0c00977. PMID 33492935. S2CID 231712587.
^ Cai, Q.Q.; Jothinathan, L.; Deng, S.H.; Ong, S.L.; Ng, H.Y.; Hu, J.Y. (2021). "Fenton- and ozone-based AOP processes for industrial effluent treatment". Advanced Oxidation Processes for Effluent Treatment Plants. pp. 199–254. doi:10.1016/b978-0-12-821011-6.00011-6. ISBN 978-0-12-821011-6. S2CID 224976088.
^ Haber, F.; Weiss, J. (1932). "Über die katalyse des hydroperoxydes" [On the catalysis of hydroperoxides]. Naturwissenschaften. 20 (51): 948–950. Bibcode:1932NW.....20..948H. doi:10.1007/BF01504715. S2CID 40200383.
^ Casado, Juan; Fornaguera, Jordi; Galan, Maria I. (January 2005). "Mineralization of aromatics in water by sunlight-assisted electro-Fenton technology in a pilot reactor". Environmental Science and Technology. 39 (6): 1843–1847. Bibcode:2005EnST...39.1843C. doi:10.1021/es0498787. PMID 15819245.
^ Brömme, H. J.; Mörke, W.; Peschke, E. (November 2002). "Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers". Journal of Pineal Research. 33 (4): 239–247. doi:10.1034/j.1600-079X.2002.02936.x. PMID 12390507. S2CID 30242100.
^ Jenner, E. L. (1973). "α,α,α′,α′-Tetramethyltetramethylene glycol". Organic Syntheses; Collected Volumes, vol. 5, p. 1026.
^ ^a ^b Cai, Q. Q.; Lee, B. C. Y.; Ong, S. L.; Hu, J. Y. (15 February 2021). "Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment–Recent advances, challenges and perspective". Water Research. 190: 116692. Bibcode:2021WatRe.19016692C. doi:10.1016/j.watres.2020.116692. PMID 33279748. S2CID 227523802.
^ Xu, Xiang-Rong; Li, Xiao-Yan; Li, Xiang-Zhong; Li, Hua-Bin (5 August 2009). "Degradation of melatonin by UV, UV/H₂O₂, Fe²⁺/H₂O₂ and UV/Fe²⁺/H₂O₂ processes". Separation and Purification Technology. 68 (2): 261–266. doi:10.1016/j.seppur.2009.05.013.
^ Tang, W. Z.; Huang, C. P. (1 December 1996). "2,4-Dichlorophenol Oxidation Kinetics by Fenton's Reagent". Environmental Technology. 17 (12): 1371–1378. Bibcode:1996EnvTe..17.1371T. doi:10.1080/09593330.1996.9618465.
^ Szpyrkowicz, Lidia; Juzzolino, Claudia; Kaul, Santosh N (1 June 2001). "A Comparative study on oxidation of disperse dyes by electrochemical process, ozone, hypochlorite and fenton reagent". Water Research. 35 (9): 2129–2136. Bibcode:2001WatRe..35.2129S. doi:10.1016/s0043-1354(00)00487-5. PMID 11358291.
^ Velichkova, Filipa; Delmas, Henri; Julcour, Carine; Koumanova, Bogdana (2017). "Heterogeneous fenton and photo-fenton oxidation for paracetamol removal using iron containing ZSM-5 zeolite as catalyst" (PDF). AIChE Journal. 63 (2): 669–679. Bibcode:2017AIChE..63..669V. doi:10.1002/aic.15369.
^ Cai, Qinqing; Lee, Brandon Chuan Yee; Ong, Say Leong; Hu, Jiangyong (9 April 2021). "Application of a Multiobjective Artificial Neural Network (ANN) in Industrial Reverse Osmosis Concentrate Treatment with a Fluidized Bed Fenton Process: Performance Prediction and Process Optimization". ACS ES&T Water. 1 (4): 847–858. doi:10.1021/acsestwater.0c00192. S2CID 234110033.
^ Matavos-Aramyan, S.; Moussavi, M.; Matavos-Aramyan, H.; Roozkhosh, S. (2017). "Cryptosporidium-contaminated water disinfection by a novel Fenton process". Free Radical Biology and Medicine. 106: 158–167. doi:10.1016/j.freeradbiomed.2017.02.030. PMID 28212822. S2CID 3918519.
^ Robbins; Cotran (2008). Pathologic basis of disease (7th ed.). Elsevier. p. 16. ISBN 978-0-8089-2302-2.
^ Lapointe, Marc (14 June 2004). "Iron supplementation in the intensive care unit: when, how much, and by what route?". Critical Care. 8 (2): S37-41. doi:10.1186/cc2825. PMC 3226152. PMID 15196322.
^ Chen, Yan-Jhang; Fan, Tang-Yu; Wang, Li-Pang; Cheng, Ta-Wui; Chen, Shiao-Shing; Yuan, Min-Hao; Cheng, Shikun (2020-02-18). "Application of Fenton Method for the Removal of Organic Matter in Sewage Sludge at Room Temperature". Sustainability. 12 (4): 1518. doi:10.3390/su12041518. ISSN 2071-1050.
^ Goldstein, S.; Meyerstein, D.; Czapski, G. (October 1993). "The Fenton reagents". S Goldstein et al. Free Radic Biol Med. 15 (4): 435–445. doi:10.1016/0891-5849(93)90043-t. PMID 8225025.

External links

Reference Library Peroxide Applications
Companies that use Fenton's Reagent for chemical remediation: ORIN

[1] Hemond, Harold (2015). Chemical Fate and Transport in the Environment (3rd ed.). Elsevier. p. 287. ISBN 9780123982568.

[Koppenol1993-2] Koppenol, W. H. (1 December 1993). "The centennial of the Fenton reaction". Free Radical Biology and Medicine. 15 (6): 645–651. doi:10.1016/0891-5849(93)90168-t. PMID 8138191.

[Fenton1894-3] Fenton, H. J. H. (1894). "Oxidation of tartaric acid in presence of iron". Journal of the Chemical Society, Transactions. 65 (65): 899–911. doi:10.1039/ct8946500899.

[4] Hayyan, M.; Hashim, M. A.; Al Nashef, I. M. (2016). "Superoxide ion: Generation and chemical implications". Chemical Reviews. 116 (5): 3029–3085. doi:10.1021/acs.chemrev.5b00407. PMID 26875845.

[5] Tang, Zhongmin; Zhao, Peiran; Wang, Han; Liu, Yanyan; Bu, Wenbo (2021). "Biomedicine Meets Fenton Chemistry". Chemical Reviews. 121 (4): 1981–2019. doi:10.1021/acs.chemrev.0c00977. PMID 33492935. S2CID 231712587.

[6] Cai, Q.Q.; Jothinathan, L.; Deng, S.H.; Ong, S.L.; Ng, H.Y.; Hu, J.Y. (2021). "Fenton- and ozone-based AOP processes for industrial effluent treatment". Advanced Oxidation Processes for Effluent Treatment Plants. pp. 199–254. doi:10.1016/b978-0-12-821011-6.00011-6. ISBN 978-0-12-821011-6. S2CID 224976088.

[Haber_Weiss_1932-7] Haber, F.; Weiss, J. (1932). "Über die katalyse des hydroperoxydes" [On the catalysis of hydroperoxides]. Naturwissenschaften. 20 (51): 948–950. Bibcode:1932NW.....20..948H. doi:10.1007/BF01504715. S2CID 40200383.

[8] Casado, Juan; Fornaguera, Jordi; Galan, Maria I. (January 2005). "Mineralization of aromatics in water by sunlight-assisted electro-Fenton technology in a pilot reactor". Environmental Science and Technology. 39 (6): 1843–1847. Bibcode:2005EnST...39.1843C. doi:10.1021/es0498787. PMID 15819245.

[9] Brömme, H. J.; Mörke, W.; Peschke, E. (November 2002). "Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers". Journal of Pineal Research. 33 (4): 239–247. doi:10.1034/j.1600-079X.2002.02936.x. PMID 12390507. S2CID 30242100.

[10] Jenner, E. L. (1973). "α,α,α′,α′-Tetramethyltetramethylene glycol". Organic Syntheses; Collected Volumes, vol. 5, p. 1026.

[Cai_et_al_2021-11] Cai, Q. Q.; Lee, B. C. Y.; Ong, S. L.; Hu, J. Y. (15 February 2021). "Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment–Recent advances, challenges and perspective". Water Research. 190: 116692. Bibcode:2021WatRe.19016692C. doi:10.1016/j.watres.2020.116692. PMID 33279748. S2CID 227523802.

[12] Xu, Xiang-Rong; Li, Xiao-Yan; Li, Xiang-Zhong; Li, Hua-Bin (5 August 2009). "Degradation of melatonin by UV, UV/H₂O₂, Fe²⁺/H₂O₂ and UV/Fe²⁺/H₂O₂ processes". Separation and Purification Technology. 68 (2): 261–266. doi:10.1016/j.seppur.2009.05.013.

[13] Tang, W. Z.; Huang, C. P. (1 December 1996). "2,4-Dichlorophenol Oxidation Kinetics by Fenton's Reagent". Environmental Technology. 17 (12): 1371–1378. Bibcode:1996EnvTe..17.1371T. doi:10.1080/09593330.1996.9618465.

[14] Szpyrkowicz, Lidia; Juzzolino, Claudia; Kaul, Santosh N (1 June 2001). "A Comparative study on oxidation of disperse dyes by electrochemical process, ozone, hypochlorite and fenton reagent". Water Research. 35 (9): 2129–2136. Bibcode:2001WatRe..35.2129S. doi:10.1016/s0043-1354(00)00487-5. PMID 11358291.

[15] Velichkova, Filipa; Delmas, Henri; Julcour, Carine; Koumanova, Bogdana (2017). "Heterogeneous fenton and photo-fenton oxidation for paracetamol removal using iron containing ZSM-5 zeolite as catalyst" (PDF). AIChE Journal. 63 (2): 669–679. Bibcode:2017AIChE..63..669V. doi:10.1002/aic.15369.

[16] Cai, Qinqing; Lee, Brandon Chuan Yee; Ong, Say Leong; Hu, Jiangyong (9 April 2021). "Application of a Multiobjective Artificial Neural Network (ANN) in Industrial Reverse Osmosis Concentrate Treatment with a Fluidized Bed Fenton Process: Performance Prediction and Process Optimization". ACS ES&T Water. 1 (4): 847–858. doi:10.1021/acsestwater.0c00192. S2CID 234110033.

[17] Matavos-Aramyan, S.; Moussavi, M.; Matavos-Aramyan, H.; Roozkhosh, S. (2017). "Cryptosporidium-contaminated water disinfection by a novel Fenton process". Free Radical Biology and Medicine. 106: 158–167. doi:10.1016/j.freeradbiomed.2017.02.030. PMID 28212822. S2CID 3918519.

[18] Robbins; Cotran (2008). Pathologic basis of disease (7th ed.). Elsevier. p. 16. ISBN 978-0-8089-2302-2.

[19] Lapointe, Marc (14 June 2004). "Iron supplementation in the intensive care unit: when, how much, and by what route?". Critical Care. 8 (2): S37-41. doi:10.1186/cc2825. PMC 3226152. PMID 15196322.

[20] Chen, Yan-Jhang; Fan, Tang-Yu; Wang, Li-Pang; Cheng, Ta-Wui; Chen, Shiao-Shing; Yuan, Min-Hao; Cheng, Shikun (2020-02-18). "Application of Fenton Method for the Removal of Organic Matter in Sewage Sludge at Room Temperature". Sustainability. 12 (4): 1518. doi:10.3390/su12041518. ISSN 2071-1050.

[21] Goldstein, S.; Meyerstein, D.; Czapski, G. (October 1993). "The Fenton reagents". S Goldstein et al. Free Radic Biol Med. 15 (4): 435–445. doi:10.1016/0891-5849(93)90043-t. PMID 8225025.

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@@ Line 1: / Line 1: @@
-{{short description|Strongly oxidizing solution of hydrogen peroxide mixed with dissolved iron as catalyst}}
+{{Short description|Strongly oxidizing solution of hydrogen peroxide mixed with dissolved iron as catalyst}}
-'''Fenton's reagent''' is a solution of [[hydrogen peroxide]] (H<sub>2</sub>O<sub>2</sub>) with [[ferrous]] iron (typically [[iron(II) sulfate]], FeSO<sub>4</sub>) as a [[catalyst]] that is used to [[oxidize]] [[contaminants]] or [[waste water]]s. Fenton's reagent can be used to destroy [[organic compound]]s such as [[trichloroethylene]] (TCE) and [[tetrachloroethylene]] (perchloroethylene, PCE). It was developed in the 1890s by [[Henry John Horstman Fenton]] as an analytical reagent.<ref name="Koppenol1993">{{cite journal|last1=Koppenol|first1=W.H.|title=The centennial of the Fenton reaction|journal=Free Radical Biology and Medicine|volume=15|issue=6|year=1993|pages=645–651|issn=0891-5849|doi=10.1016/0891-5849(93)90168-T|pmid=8138191}}</ref><ref name="Fenton1894">{{cite journal
+'''Fenton's reagent''' is a solution of [[hydrogen peroxide]] (H<sub>2</sub>O<sub>2</sub>) and an iron catalyst (typically [[iron(II) sulfate]], FeSO<sub>4</sub>).<ref>{{Cite book |last=Hemond |first=Harold |title=Chemical Fate and Transport in the Environment |publisher=Elsevier |year=2015 |isbn=9780123982568 |edition=3rd |pages=287}}</ref> It is used to [[oxidize]] [[contaminants]] or [[waste water]] as part of an [[advanced oxidation process]]. Fenton's reagent can be used to destroy [[organic compound]]s such as [[trichloroethylene]] and [[tetrachloroethylene]] (perchloroethylene). It was developed in the 1890s by [[Henry John Horstman Fenton]] as an analytical reagent.<ref name="Koppenol1993">{{cite journal |last1=Koppenol |first1=W. H. |title=The centennial of the Fenton reaction |journal=Free Radical Biology and Medicine |date=1 December 1993 |volume=15 |issue=6 |pages=645–651 |doi=10.1016/0891-5849(93)90168-t |pmid=8138191 }}</ref><ref name="Fenton1894">{{cite journal
  | doi = 10.1039/ct8946500899
  | title = Oxidation of tartaric acid in presence of iron
- | author = Fenton H.J.H.
+ | last = Fenton|first= H. J. H.
- | journal = J. Chem. Soc., Trans.
+ | journal = Journal of the Chemical Society, Transactions
  | volume =  65
  | issue = 65
@@ Line 10: / Line 11: @@
  | year = 1894
  | url = https://books.google.com/books?id=Deo2AAAAYAAJ&pg=PA899
- }}</ref><ref>Hayyan M., Hashim M.A., AlNashef I.M., Superoxide ion: Generation and chemical implications. Chem. Rev., 2016, 116 (5), pp 3029–3085. [[DOI: 10.1021/acs.chemrev.5b00407]]</ref>
+ }}</ref><ref>{{cite journal|last1=Hayyan |first1=M. |last2=Hashim |first2=M. A. |last3=Al Nashef |first3=I. M. |title=Superoxide ion: Generation and chemical implications |journal=Chemical Reviews |date=2016 |volume=116 |issue=5 |pages=3029–3085 |doi=10.1021/acs.chemrev.5b00407|pmid=26875845 |doi-access=free }}</ref>
-==Overview ==
+==Reactions ==
-Iron(II) is oxidized by hydrogen peroxide to [[iron(III)]], forming a [[hydroxyl radical]] and a [[hydroxide ion]] in the process. Iron(III) is then reduced back to iron(II) by another molecule of hydrogen peroxide, forming a [[hydroperoxyl]] radical and a [[hydrogen atom|proton]]. The net effect is a [[disproportionation]] of hydrogen peroxide to create two different oxygen-radical species, with water (H<sup>+</sup>&nbsp;+&nbsp;OH<sup>−</sup>) as a byproduct.
+[[Iron(II)]] is oxidized by hydrogen peroxide to [[iron(III)]], forming a [[hydroxyl radical]] and a [[hydroxide ion]] in the process. Iron(III) is then reduced back to iron(II) by another molecule of hydrogen peroxide, forming a [[hydroperoxyl]] radical and a [[hydrogen atom|proton]]. The net effect is a [[disproportionation]] of hydrogen peroxide to create two different oxygen-radical species, with water (H<sup>+</sup>&nbsp;+&nbsp;OH<sup>−</sup>) as a byproduct.<ref>{{cite journal |doi=10.1021/acs.chemrev.0c00977 |title=Biomedicine Meets Fenton Chemistry |date=2021 |last1=Tang |first1=Zhongmin |last2=Zhao |first2=Peiran |last3=Wang |first3=Han |last4=Liu |first4=Yanyan |last5=Bu |first5=Wenbo |journal=Chemical Reviews |volume=121 |issue=4 |pages=1981–2019 |pmid=33492935 |s2cid=231712587 }}</ref>
-{{NumBlk|:| Fe<sup>2+</sup> + H<sub>2</sub>O<sub>2</sub> → Fe<sup>3+</sup> + HO• + OH<sup>−</sup>|{{EquationRef|1}}}}
+{{NumBlk|:| Fe<sup>2+</sup> + H<sub>2</sub>O<sub>2</sub> → Fe<sup>3+</sup> + HO<sup>•</sup> + OH<sup>−</sup>|{{EquationRef|1}}}}
-{{NumBlk|:| Fe<sup>3+</sup> + H<sub>2</sub>O<sub>2</sub> → Fe<sup>2+</sup> + HOO• + H<sup>+</sup>|{{EquationRef|2}}}}
+{{NumBlk|:| Fe<sup>3+</sup> + H<sub>2</sub>O<sub>2</sub> → Fe<sup>2+</sup> + HOO<sup>•</sup> + H<sup>+</sup>|{{EquationRef|2}}}}
-{{NumBlk|:| 2 H<sub>2</sub>O<sub>2</sub> →  HO• + HOO• + H<sub>2</sub>O|{{EquationRef|net reaction: 1+2}}}}
+{{NumBlk|:| 2 H<sub>2</sub>O<sub>2</sub> →  HO<sup>•</sup> + HOO<sup>•</sup> + H<sub>2</sub>O|{{EquationRef|net reaction: 1+2}}}}
-The [[free radical]]s generated by this process then engage in secondary reactions. For example, the hydroxyl is a powerful, non-selective oxidant.<ref>{{Citation|last=Cai|first=Q. Q.|title=11 - Fenton- and ozone-based AOP processes for industrial effluent treatment|date=2021-01-01|url=https://www.sciencedirect.com/science/article/pii/B9780128210116000116|work=Advanced Oxidation Processes for Effluent Treatment Plants|pages=199–254|editor-last=Shah|editor-first=Maulin P.|publisher=Elsevier|language=en|doi=10.1016/b978-0-12-821011-6.00011-6|isbn=978-0-12-821011-6|access-date=2021-04-08|last2=Jothinathan|first2=L.|last3=Deng|first3=S. H.|last4=Ong|first4=S. L.|last5=Ng|first5=H. Y.|last6=Hu|first6=J. Y.}}</ref> Oxidation of an organic compound by Fenton's reagent is rapid and [[exothermic]] and results in the oxidation of contaminants to primarily carbon dioxide and water.
+The [[free radical]]s generated by this process engage in secondary reactions. For example, the hydroxyl is a powerful, non-selective oxidant.<ref>{{cite book |doi=10.1016/b978-0-12-821011-6.00011-6 |chapter=Fenton- and ozone-based AOP processes for industrial effluent treatment |title=Advanced Oxidation Processes for Effluent Treatment Plants |year=2021 |last1=Cai |first1=Q.Q. |last2=Jothinathan |first2=L. |last3=Deng |first3=S.H. |last4=Ong |first4=S.L. |last5=Ng |first5=H.Y. |last6=Hu |first6=J.Y. |pages=199–254 |isbn=978-0-12-821011-6 |s2cid=224976088 }}</ref> Oxidation of an organic compound by Fenton's reagent is rapid and [[exothermic]] and results in the oxidation of contaminants to primarily carbon dioxide and water.
-Reaction ({{EquationNote|1}}) was suggested by [[Fritz Haber|Haber]] and [[Joseph Joshua Weiss|Weiss]] in the 1930s as part of what would become the [[Haber–Weiss reaction]].<ref name="Haber_Weiss_1932">{{cite journal |author1=Haber, F.  |author2=Weiss, J. | year = 1932 | title = Über die katalyse des hydroperoxydes | trans-title= On the catalysis of hydroperoxides | journal = [[Naturwissenschaften]] | doi = 10.1007/BF01504715|volume = 20|issue = 51|pages = 948–950|bibcode = 1932NW.....20..948H|s2cid=40200383 }}</ref>
+Reaction ({{EquationNote|1}}) was suggested by [[Fritz Haber|Haber]] and [[Joseph Joshua Weiss|Weiss]] in the 1930s as part of what would become the [[Haber–Weiss reaction]].<ref name="Haber_Weiss_1932">{{cite journal |last1=Haber |first1=F.  |last2=Weiss |first2=J. | year = 1932 | title = Über die katalyse des hydroperoxydes | trans-title= On the catalysis of hydroperoxides | journal = [[Naturwissenschaften]] | doi = 10.1007/BF01504715|volume = 20|issue = 51|pages = 948–950|bibcode = 1932NW.....20..948H|s2cid=40200383 }}</ref>
-[[Iron(II) sulfate]] is typically used as the iron catalyst. The exact mechanisms of the redox cycle are uncertain, and non-OH• oxidizing mechanisms of organic compounds have also been suggested.{{citation needed|date=October 2013}} Therefore, it may be appropriate to broadly discuss ''Fenton chemistry'' rather than a specific ''Fenton reaction''.
+[[Iron(II) sulfate]] is typically used as the iron catalyst. The exact mechanisms of the redox cycle are uncertain, and non-OH<sup>•</sup> oxidizing mechanisms of organic compounds have also been suggested.{{citation needed|date=October 2013}} Therefore, it may be appropriate to broadly discuss ''Fenton chemistry'' rather than a specific ''Fenton reaction''.
-In the electro-Fenton process, hydrogen peroxide is produced ''in situ'' from the [[electrochemical reduction]] of oxygen.<ref>{{cite journal |author1=Juan Casado |author2=Jordi Fornaguera |author3=Maria I. Galan |title=Mineralization of aromatics in water by sunlight-assisted electro-Fenton technology in a pilot reactor  |journal=Environ. Sci. Technol. |volume=39 |issue=6 |pages=1843–47 |date=January 2005 |pmid= 15819245|doi= 10.1021/es0498787|url=http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2005/39/i06/abs/es0498787.html|bibcode=2005EnST...39.1843C}}</ref>
+In the electro-Fenton process, hydrogen peroxide is produced ''in situ'' from the [[electrochemical reduction]] of oxygen.<ref>{{cite journal |first1=Juan |last1=Casado |first2=Jordi |last2=Fornaguera |first3=Maria I. |last3=Galan |title=Mineralization of aromatics in water by sunlight-assisted electro-Fenton technology in a pilot reactor  |journal=Environmental Science and Technology |volume=39 |issue=6 |pages=1843–1847 |date=January 2005 |pmid= 15819245|doi= 10.1021/es0498787|bibcode=2005EnST...39.1843C}}</ref>
 Fenton's reagent is also used in [[organic synthesis]] for the [[hydroxylation]] of [[arene]]s in a [[radical substitution]] reaction such as the classical conversion of [[benzene]] into [[phenol]].
-{{NumBlk|:| C<sub>6</sub>H<sub>6</sub> + FeSO<sub>4</sub> + H<sub>2</sub>O<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>OH|{{EquationRef|3}}}}
+{{NumBlk|:| C<sub>6</sub>H<sub>6</sub> + FeSO<sub>4</sub> + H<sub>2</sub>O<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>OH + (byproducts)|{{EquationRef|3}}}}
-An example hydroxylation reaction involves the [[Organic redox reaction|oxidation]] of [[barbituric acid]] to [[alloxane]].<ref>{{cite journal |vauthors=Brömme HJ, Mörke W, Peschke E |title=Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers |journal=J. Pineal Res. |volume=33 |issue=4 |pages=239–47 |date=November 2002 |pmid=12390507 |doi= 10.1034/j.1600-079X.2002.02936.x|s2cid=30242100 }}</ref> Another application of the reagent in organic synthesis is in [[coupling reaction]]s of alkanes. As an example [[Tert-Butanol|''tert''-butanol]] is dimerized with Fenton's reagent and [[sulfuric acid]] to 2,5-dimethyl-2,5-hexanediol.<ref>{{OrgSynth | collvol = 5  |  collvolpages = 1026 | prep = cv5p1026 | title =  α,α,α',α'-Tetramethyltetramethylene  glycol | author = E. L. Jenner | year = 1973}}</ref> Fenton's reagent is also widely used in the field of environmental science for [[water purification]] and [[Environmental remediation|soil remediation]]. Various hazardous wastewater were reported to be effectively degraded through Fenton's reagent<ref>{{Cite journal|last=Cai|first=Q. Q.|last2=Lee|first2=B. C. Y.|last3=Ong|first3=S. L.|last4=Hu|first4=J. Y.|date=2021-02-15|title=Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment–Recent advances, challenges and perspective|url=https://www.sciencedirect.com/science/article/pii/S0043135420312276|journal=Water Research|language=en|volume=190|pages=116692|doi=10.1016/j.watres.2020.116692|issn=0043-1354}}</ref> .
+An example hydroxylation reaction involves the [[Organic redox reaction|oxidation]] of [[barbituric acid]] to [[alloxane]].<ref>{{cite journal |last1=Brömme |first1=H. J. |last2=Mörke |first2=W. |last3=Peschke |first3=E. |title=Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers |journal=Journal of Pineal Research |volume=33 |issue=4 |pages=239–247 |date=November 2002 |pmid=12390507 |doi= 10.1034/j.1600-079X.2002.02936.x|s2cid=30242100 }}</ref> Another application of the reagent in organic synthesis is in [[coupling reaction]]s of alkanes. As an example [[Tert-Butanol|''tert''-butanol]] is dimerized with Fenton's reagent and [[sulfuric acid]] to 2,5-dimethyl-2,5-hexanediol.<ref>{{OrgSynth | collvol = 5  |  collvolpages = 1026 | prep = cv5p1026 | title =  α,α,α′,α′-Tetramethyltetramethylene  glycol | first= E. L. |last=Jenner | year = 1973}}</ref> Fenton's reagent is also widely used in the field of environmental science for [[water purification]] and [[Environmental remediation|soil remediation]]. Various hazardous wastewater were reported to be effectively degraded through Fenton's reagent.<ref name="Cai et al 2021">{{cite journal |last1=Cai |first1=Q. Q. |last2=Lee |first2=B. C. Y. |last3=Ong |first3=S. L. |last4=Hu |first4=J. Y. |title=Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment–Recent advances, challenges and perspective |journal=Water Research |date=15 February 2021 |volume=190 |pages=116692 |doi=10.1016/j.watres.2020.116692 |pmid=33279748 |bibcode=2021WatRe.19016692C |s2cid=227523802 }}</ref>
 ==Effect of pH on formation of free radicals==
-pH affects the reaction rate due to a variety of different reasons. At a low pH, complexation of Fe<sup>2+</sup> also occurs, leading to lower availability of Fe<sup>2+</sup> to form [[Free radical|reactive oxidative species]] (OH•)<ref>{{Cite journal|last=Xu|first=Xiang-Rong|last2=Li|first2=Xiao-Yan|last3=Li|first3=Xiang-Zhong|last4=Li|first4=Hua-Bin|date=2009-08-05|title=Degradation of melatonin by UV, UV/H2O2, Fe2+/H2O2 and UV/Fe2+/H2O2 processes|url=https://www.sciencedirect.com/science/article/pii/S1383586609002202|journal=Separation and Purification Technology|language=en|volume=68|issue=2|pages=261–266|doi=10.1016/j.seppur.2009.05.013|issn=1383-5866}}</ref>. Lower pH also results in the scavenging of <sup>•</sup>OH by excess H<sup>+</sup> <ref>{{Cite journal|last=Tang|first=W. Z.|last2=Huang|first2=C. P.|date=1996-12-01|title=2,4-Dichlorophenol Oxidation Kinetics by Fenton's Reagent|url=https://www.tandfonline.com/doi/abs/10.1080/09593330.1996.9618465|journal=Environmental Technology|volume=17|issue=12|pages=1371–1378|doi=10.1080/09593330.1996.9618465|issn=0959-3330}}</ref>, hence reducing its reaction rate. Whereas at high pH, the reaction slows down due to precipitation of Fe(OH)<sub>3</sub>, lowering the concentration of the Fe<sup>3+</sup> species in solution.<ref>{{Cite journal|last=Cai|first=Q. Q.|last2=Lee|first2=B. C. Y.|last3=Ong|first3=S. L.|last4=Hu|first4=J. Y.|date=2021-02-15|title=Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment–Recent advances, challenges and perspective|url=https://www.sciencedirect.com/science/article/pii/S0043135420312276|journal=Water Research|language=en|volume=190|pages=116692|doi=10.1016/j.watres.2020.116692|issn=0043-1354}}</ref> [[Solubility]] of iron species is directly governed by the solution's [[pH]]. Fe<sup>3+</sup> is about 100 times less soluble than Fe<sup>2+</sup> in natural water at near-neutral pH, the ferric ion concentration is the limiting factor for the reaction rate. Under high pH conditions, the stability of the H<sub>2</sub>O<sub>2</sub> is also affected, resulting in its self-decomposition <ref>{{Cite journal|last=Szpyrkowicz|first=Lidia|last2=Juzzolino|first2=Claudia|last3=Kaul|first3=Santosh N|date=2001-06|title=A Comparative study on oxidation of disperse dyes by electrochemical process, ozone, hypochlorite and fenton reagent|url=http://dx.doi.org/10.1016/s0043-1354(00)00487-5|journal=Water Research|volume=35|issue=9|pages=2129–2136|doi=10.1016/s0043-1354(00)00487-5|issn=0043-1354}}</ref>. Higher pH also decreased the redox potential of <sup>•</sup>OH thereby reducing its effectiveness. <ref>{{Cite journal|last=Velichkova|first=Filipa|last2=Delmas|first2=Henri|last3=Julcour|first3=Carine|last4=Koumanova|first4=Bogdana|date=2016-06-28|title=Heterogeneous fenton and photo-fenton oxidation for paracetamol removal using iron containing ZSM-5 zeolite as catalyst|url=http://dx.doi.org/10.1002/aic.15369|journal=AIChE Journal|volume=63|issue=2|pages=669–679|doi=10.1002/aic.15369|issn=0001-1541}}</ref> pH plays a crucial role in the formation of free radicals and hence the reaction performance. Thus ongoing research has been done to optimize pH and amongst other parameters for greater reaction rates.<ref>{{Cite journal|last=Cai|first=Qinqing|last2=Lee|first2=Brandon Chuan Yee|last3=Ong|first3=Say Leong|last4=Hu|first4=Jiangyong|date=2021-01-14|title=Application of a Multiobjective Artificial Neural Network (ANN) in Industrial Reverse Osmosis Concentrate Treatment with a Fluidized Bed Fenton Process: Performance Prediction and Process Optimization|url=https://doi.org/10.1021/acsestwater.0c00192|journal=ACS ES&T Water|doi=10.1021/acsestwater.0c00192}}</ref>
+[[pH]] affects the reaction rate due to a variety of reasons. At a low pH, complexation of {{chem2|Fe(2+)}} also occurs, leading to lower availability of {{chem2|Fe(2+)}} to form [[Free radical|reactive oxidative species]] (OH<sup>•</sup>).<ref>{{cite journal |last1=Xu |first1=Xiang-Rong |last2=Li |first2=Xiao-Yan |last3=Li |first3=Xiang-Zhong |last4=Li |first4=Hua-Bin |title=Degradation of melatonin by UV, UV/H<sub>2</sub>O<sub>2</sub>, Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub> and UV/Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub> processes |journal=Separation and Purification Technology |date=5 August 2009 |volume=68 |issue=2 |pages=261–266 |doi=10.1016/j.seppur.2009.05.013 }}</ref> Lower pH also results in the scavenging of <sup>•</sup>OH by excess {{chem2|H+}},<ref>{{cite journal |last1=Tang |first1=W. Z. |last2=Huang |first2=C. P. |title=2,4-Dichlorophenol Oxidation Kinetics by Fenton's Reagent |journal=Environmental Technology |date=1 December 1996 |volume=17 |issue=12 |pages=1371–1378 |doi=10.1080/09593330.1996.9618465 |bibcode=1996EnvTe..17.1371T }}</ref> hence reducing its reaction rate. Whereas at high pH, the reaction slows down due to precipitation of [[Iron(III) hydroxide|Fe(OH)<sub>3</sub>]], lowering the concentration of the {{chem2|Fe(3+)}} species in solution.<ref name="Cai et al 2021"/> [[Solubility]] of iron species is directly governed by the solution's [[pH]]. {{chem2|Fe(3+)}} is about 100 times less soluble than {{chem2|Fe(2+)}} in natural water at near-neutral pH, the ferric ion concentration is the limiting factor for the reaction rate. Under high pH conditions, the stability of the H<sub>2</sub>O<sub>2</sub> is also affected, resulting in its self-decomposition.<ref>{{cite journal |last1=Szpyrkowicz |first1=Lidia |last2=Juzzolino |first2=Claudia |last3=Kaul |first3=Santosh N |title=A Comparative study on oxidation of disperse dyes by electrochemical process, ozone, hypochlorite and fenton reagent |journal=Water Research |date=1 June 2001 |volume=35 |issue=9 |pages=2129–2136 |doi=10.1016/s0043-1354(00)00487-5 |pmid=11358291 |bibcode=2001WatRe..35.2129S }}</ref> Higher pH also decreased the [[Reduction potential|redox potential]] of <sup>•</sup>OH thereby reducing its effectiveness.<ref>{{cite journal |last1=Velichkova |first1=Filipa |last2=Delmas |first2=Henri |last3=Julcour |first3=Carine |last4=Koumanova |first4=Bogdana |title=Heterogeneous fenton and photo-fenton oxidation for paracetamol removal using iron containing ZSM-5 zeolite as catalyst |journal=AIChE Journal |date=2017 |volume=63 |issue=2 |pages=669–679 |doi=10.1002/aic.15369 |bibcode=2017AIChE..63..669V |url=http://oatao.univ-toulouse.fr/20832/1/Velichkova_20832.pdf }}</ref> pH plays a crucial role in the formation of free radicals and hence the reaction performance. Thus ongoing research has been done to optimize pH and amongst other parameters for greater reaction rates.<ref>{{cite journal |last1=Cai |first1=Qinqing |last2=Lee |first2=Brandon Chuan Yee |last3=Ong |first3=Say Leong |last4=Hu |first4=Jiangyong |title=Application of a Multiobjective Artificial Neural Network (ANN) in Industrial Reverse Osmosis Concentrate Treatment with a Fluidized Bed Fenton Process: Performance Prediction and Process Optimization |journal=ACS ES&T Water |date=9 April 2021 |volume=1 |issue=4 |pages=847–858 |doi=10.1021/acsestwater.0c00192 |s2cid=234110033 }}</ref>
-{| class="wikitable"
+:{| class="wikitable"
 |+Impacts of operation pH on reaction rate
 ! rowspan="2" |Low pH
-|Formation of [Fe(H<sub>2</sub>O)<sub>6</sub>] <sup>2+</sup> complex, hence reducing Fe<sup>2+</sup> for  radical generation
+|Formation of [Fe(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> complex, hence reducing Fe<sup>2+</sup> for  radical generation
 |-
 |Scavenging of <sup>•</sup>OH by excess H<sup>+</sup>
 |-
-| rowspan="3" |'''High pH'''
+! rowspan="3" |High pH
 |Lower redox potential of <sup>•</sup>OH
 |-
 |Self-decomposition of H<sub>2</sub>O<sub>2</sub> due to decreased stability at high pH
 |-
-|Precipitation of Fe(OH)<sub>3</sub> species in solution
+|Precipitation of [[Iron(III) oxide-hydroxide|Fe(OH)<sub>3</sub>]] species in solution
 |}
 ==Biomedical implications==
-The Fenton reaction has different implications in biology because it involves the formation of free radicals by chemical species naturally present in the cell under ''[[in vivo]]'' conditions.<ref>{{cite journal |last1=Matavos-Aramyan |first1=S |last2=Moussavi |first2=M |last3=Matavos-Aramyan |first3=H |last4=Roozkhosh |first4=S |title=Cryptosporidium-contaminated water disinfection by a novel Fenton process |journal=Free Radical Biology and Medicine |volume=106 |date=2017 |pages=158–167 |doi=10.1016/j.freeradbiomed.2017.02.030 |pmid=28212822 |s2cid=3918519 }}</ref> [[Transition-metal]] ions such as [[iron]] and [[copper]] can donate or accept [[Unpaired electron|free electrons]] via intracellular reactions and so contribute to the formation, or at the contrary to the scavenging, of [[free radical]]s. In oxygen respirating organisms, most of the intracellular iron is in the [[ferric]] (Fe<sup>3+</sup>) state{{citation needed|date=May 2019}} and must therefore be reduced to the [[ferrous]] (Fe<sup>2+</sup>) form to take part in the Fenton reaction. [[Superoxide]] ions and transition metals act in a synergistic way in the appearance of free radical damages.<ref>{{cite book|author=Robbins|author2=Cotran|name-list-style=amp|title=Pathologic basis of disease|edition=7th|year=2008|publisher=Elsevier|isbn=9780808923022|pages=16}}</ref> Therefore, although the clinical significance is still unclear, it is one of the viable reasons to avoid iron supplementation in patients with active infections, whereas other reasons include iron-mediated infections.<ref>{{Cite journal|last=Lapointe|first=Marc|date=2004-01-01|title=Iron supplementation in the intensive care unit: when, how much, and by what route?|journal=Critical Care|volume=8|issue=2|pages=S37–41|doi=10.1186/cc2825|issn=1364-8535|pmc=3226152|pmid=15196322}}</ref>
+The Fenton reaction has different implications in biology because it involves the formation of free radicals by chemical species naturally present in the cell under ''[[in vivo]]'' conditions.<ref>{{cite journal |last1=Matavos-Aramyan |first1=S. |last2=Moussavi |first2=M. |last3=Matavos-Aramyan |first3=H. |last4=Roozkhosh |first4=S. |title=Cryptosporidium-contaminated water disinfection by a novel Fenton process |journal=Free Radical Biology and Medicine |volume=106 |date=2017 |pages=158–167 |doi=10.1016/j.freeradbiomed.2017.02.030 |pmid=28212822 |s2cid=3918519 }}</ref> [[Transition-metal]] ions such as [[iron]] and [[copper]] can donate or accept [[Unpaired electron|free electrons]] via intracellular reactions and so contribute to the formation, or at the contrary to the scavenging, of [[free radical]]s. [[Superoxide]] ions and transition metals act in a synergistic way in the appearance of free radical damages.<ref>{{cite book|author=Robbins|author2=Cotran|title=Pathologic basis of disease|edition=7th|year=2008|publisher=Elsevier|isbn=978-0-8089-2302-2|page=16}}</ref> Therefore, although the clinical significance is still unclear, it is one of the viable reasons to avoid iron supplementation in patients with active infections, whereas other reasons include iron-mediated infections.<ref>{{cite journal |last1=Lapointe |first1=Marc |title=Iron supplementation in the intensive care unit: when, how much, and by what route? |journal=Critical Care |date=14 June 2004 |volume=8 |issue=2 |pages=S37-41 |doi=10.1186/cc2825 |pmid=15196322 |pmc=3226152 |doi-access=free }}</ref>
+== Applications ==
+{{See also|Advanced oxidation process}}
+Fenton's reagent is used as a sewage treatment agent.<ref>{{Cite journal |last1=Chen |first1=Yan-Jhang |last2=Fan |first2=Tang-Yu |last3=Wang |first3=Li-Pang |last4=Cheng |first4=Ta-Wui |last5=Chen |first5=Shiao-Shing |last6=Yuan |first6=Min-Hao |last7=Cheng |first7=Shikun |date=2020-02-18 |title=Application of Fenton Method for the Removal of Organic Matter in Sewage Sludge at Room Temperature |journal=Sustainability |volume=12 |issue=4 |pages=1518 |doi=10.3390/su12041518 |issn=2071-1050|doi-access=free }}</ref>
+Fenton's reagent can be used in different chemical processes that supply [[Hydroxy group|hydroxyl]] ion or oxidize certain compounds:{{Citation needed|date=May 2024}}
+* The first stage of Fenton's reaction (oxidation of Fe<sup>3+</sup> with [[hydrogen peroxide]]) is used in [[Haber–Weiss reaction]]
+* Fenton's reagent can be used in organic synthesis reactions: e.g. hydroxylation of [[Aromatic compound|arenes]] via a [[Radical substitution|free radical substitution]]
+* Conversion of [[benzene]] into [[phenol]] by using Fenton's reagent
+* Oxidation of barbituric acid into alloxan.
+* Coupling reactions of alkanes
+== Fenton-like reagent ==
+Mixtures of {{chem2|Fe(2+)}} and {{chem2|H2O2}} are called Fenton reagent. If {{chem2|Fe(2+)}} is replaced by {{chem2|Fe(3+)}}, it is called Fenton-like reagent.
+Numerous transition metal ions and their complexes in their lower oxidation states (L<sub>m</sub>M<sup>n+</sup>) were found to have the oxidative features of the Fenton reagent, and, therefore, the mixtures of these metal compounds with {{chem2|H2O2}} were named "Fenton-like" reagents.<ref>{{cite journal|title=The Fenton reagents|journal=S Goldstein et al. Free Radic Biol Med. |date=October 1993|pmid=8225025 |last1=Goldstein |first1=S. |last2=Meyerstein |first2=D. |last3=Czapski |first3=G. |volume=15 |issue=4 |pages=435–445 |doi=10.1016/0891-5849(93)90043-t }}</ref>
 ==See also==
@@ Line 58: / Line 76: @@
 == References ==
+{{Reflist}}
-<references/>
 == Further reading ==
 *{{cite journal
  | title = The Fenton reagents
- |author1=Goldstein Sara |author2=Meyerstein Dan |author3=Czapski Gidon | journal = Free Radical Biology and Medicine
+ |last1=Goldstein |first1=Sara |last2=Meyerstein |first2=Dan |last3=Czapski |first3=Gidon | journal = Free Radical Biology and Medicine
  | volume = 15
  | issue = 4
@@ Line 71: / Line 89: @@
  | pmid = 8225025
 }}
-* Barbusiński K. (2009). [http://tchie.uni.opole.pl/freeECE/S_16_3/Barbusinski_16(3).pdf "Fenton Reaction – Controversy concerning the chemistry".] ''Ecological Chemistry and Engineering'', Vol 16, N° 3, pp.&nbsp;347–358.
+* {{cite journal|last=Barbusiński |first=K. |date=2009 |url=http://tchie.uni.opole.pl/freeECE/S_16_3/Barbusinski_16(3).pdf |title=Fenton Reaction – Controversy concerning the chemistry |journal=Ecological Chemistry and Engineering |volume=16 |number=3 |pages=347–358}}
 ==External links==