Spectrophotometric evidence for the formation of short-lived hypomanganate(V) and manganate(VI) transient species during the oxidation of K-carrageenan by alkaline permanganate

Ahmed, Gamal A.; Fawzy, Ahmed; Hassan, Refat M.

doi:10.1016/j.carres.2007.03.022

Cited by 29 publications

(22 citation statements)

References 28 publications

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“…The experimental results in the present redox reaction indicated that the oxidation kinetics was complex in nature. It has been reported that the alcoholic polysaccharides possess high affinity for deprotonation in alkaline solutions to give the more reactive alkoxides prior to the rate‐determining step as follows:

{((), PS)}_{n} + O H^{-} ⇌ {(P S^{-})}_{n} + {normalH}_{2} O

where PS represents the alcoholic polysaccharides and PS − is the corresponding alkoxide formed. If such deprotonation occurs in the present work, the oxidation process should have been occurred between two negative charge anions as reactive species, hexacyanoferrate(III) and the formed alkoxide, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The experimental results in the present redox reaction indicated that the oxidation kinetics was complex in nature. It has been reported that the alcoholic polysaccharides possess high affinity for deprotonation in alkaline solutions 22,23,[42][43][44][45] to T A B L E 3 The activation parameters of the second-order rate constant (k n ) in the oxidation of pectin along with that for oxidation of other polysaccharides by alkaline hexacyanoferrate(III) give the more reactive alkoxides prior to the rate-determining step as follows:…”

Section: Discussionmentioning

confidence: 99%

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A promising methyl ester of pectic acid polysaccharide in biomedicine and pharmaceutics applications: Oxidation of methyl ester of pectic acid by alkaline hexacyanoferrate(III). A kinetic and mechanistic orientation

Hassan

Ibrahim²

2019

Int J of Chemical Kinetics

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The oxidation of methyl ester of pectic acid (pectin) (PEC) by a hexacyanoferrate(III) ion at a constant ionic strength of 0.1 mol dm−3 has been investigated spectrophotometrically. The oxidation rates were found to increase with increasing the alkali concentration, indicating that the nature of reaction was base catalyzed. The agreement of [pectin] dependence of the rate constants to the Michaelis‐Menten kinetics proves the formation of 1:1 intermediate complex prior to the rate‐determining step. The deviation of the pseudo–first‐order curves from linearity after 65‐70% of reaction completion indicates the interference of some oxidation products during the reaction progression. The oxidation process was proceeding via a free‐radical intervention mechanism. The activation parameters have been evaluated, and a suitable reaction mechanism is suggested and discussed.

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“…The experimental results in the present redox reaction indicated that the oxidation kinetics was complex in nature. It has been reported that the alcoholic polysaccharides possess high affinity for deprotonation in alkaline solutions to give the more reactive alkoxides prior to the rate‐determining step as follows:

{((), PS)}_{n} + O H^{-} ⇌ {(P S^{-})}_{n} + {normalH}_{2} O

Section: Discussionmentioning

confidence: 99%

“…The experimental results in the present redox reaction indicated that the oxidation kinetics was complex in nature. It has been reported that the alcoholic polysaccharides possess high affinity for deprotonation in alkaline solutions 22,23,[42][43][44][45] to T A B L E 3 The activation parameters of the second-order rate constant (k n ) in the oxidation of pectin along with that for oxidation of other polysaccharides by alkaline hexacyanoferrate(III) give the more reactive alkoxides prior to the rate-determining step as follows:…”

Section: Discussionmentioning

confidence: 99%

A promising methyl ester of pectic acid polysaccharide in biomedicine and pharmaceutics applications: Oxidation of methyl ester of pectic acid by alkaline hexacyanoferrate(III). A kinetic and mechanistic orientation

Hassan

Ibrahim²

2019

Int J of Chemical Kinetics

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“…(6)- (11)) [15,[23][24][25]: (11)), and therefore their effect on the degradation of these CPs is negligible [26,27]. But the in situ formed MnO 2 could oxidize phenols and even autocatalyze permanganate oxidation and therefore enhance the removal efficiency of phenolic chemicals in weakly acidic conditions [28,29].…”

Section: Effect Of Phmentioning

confidence: 97%

Kinetics study on the oxidation of chlorophenols by permanganate

Shao

Zou

Wang

et al. 2015

Desalination and Water Treatment

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A B S T R A C TThe kinetics of the oxidation of chlorophenols (CPs) by potassium permanganate was studied in the present study, along with the changes in oxidant dosage, pH, temperature, and real water matrices. The reactions between permanganate and three kinds of CPs, i.e. 4-chlorophenol (4-MCP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP), are second order overall and first-order with respect to each reactant. The degradation rates of the CPs increase with increasing permanganate dosage or temperature. pH plays an important role during permanganate oxidation. With the increase in pH from 4.0 to 10.0, the reaction rates of 4-MCP and 2,4-DCP decrease first and then increase, and finally decrease rapidly when pH > pK a , while the rates of 2,4,6-TCP decrease continuously. The degradation rates of the CPs are obviously higher in real water than in pure water. The reaction rate follows the order of 2,4,6-TCP > 2,4-DCP > 4-MCP under acidic conditions, and follows the reverse order under alkaline conditions in both pure water and real water.

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“…On the other hand, the produced reactive intermediates in the reaction of permanganate with humic acid can be further reduced to lower valence of manganese species either by estrone or by humic acid, or may undergo disproportionation or oxidation by MnO 2 4 to other oxidation states of manganese ( Jaky & Simon-Trompler 2002;Wiberg et al 2006;Ahmed et al 2007). However, it is possible that the selective reaction between estrone and those reactive species may cause the decrease of estrone concencetration correspondingly.…”

Section: Effect Of Humic Acid On Estrone Degradationmentioning

confidence: 98%

Effect of humic acid on the oxidation of phenolic endocrine disrupting chemicals by permanganate

Shao

Yang

et al. 2010

Journal of Water Supply: Research and Technology-Aqua

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The effect of dissolved humic acid on the oxidation of phenolic endocrine disrupting chemicals (EDCs) by potassium permanganate was studied. It was found that the degradation of phenolic EDCs is promoted to various extents by the addition of humic acid. Results show that the removal rate of estrone by permanganate within 3 min of reaction time is increased from approximately 10% in control experiments to 68% when 0.08 mg l 21 of humic acid is present in the reaction system. The oxidation experiment of nine types of phenolic EDC by permanganate confirms that the promotion induced by the addition of humic acid varies in the cases of different EDCS. Results also indicate that the promotion induced by the presence of humic acid takes effect under acidic and neutral pH conditions, while the effect of pH plays a dominant role for the degradation of phenolic EDCs under alkaline conditions. Additionally, it was found that the oxidation of estrone by permanganate is promoted through the addition of humic acid to natural waters.

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Spectrophotometric evidence for the formation of short-lived hypomanganate(V) and manganate(VI) transient species during the oxidation of K-carrageenan by alkaline permanganate

Cited by 29 publications

References 28 publications

A promising methyl ester of pectic acid polysaccharide in biomedicine and pharmaceutics applications: Oxidation of methyl ester of pectic acid by alkaline hexacyanoferrate(III). A kinetic and mechanistic orientation

A promising methyl ester of pectic acid polysaccharide in biomedicine and pharmaceutics applications: Oxidation of methyl ester of pectic acid by alkaline hexacyanoferrate(III). A kinetic and mechanistic orientation

Kinetics study on the oxidation of chlorophenols by permanganate

Effect of humic acid on the oxidation of phenolic endocrine disrupting chemicals by permanganate

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