scholarly journals Insights into the generation of hydroxyl radicals from H2O2 decomposition by the combination of Fe2+ and chloranilic acid

2021 ◽  
Author(s):  
M. I. Ahmad ◽  
N. Bensalah
Keyword(s):  
Carboxylic Acids ◽  
Hydroxyl Radicals ◽  
Chemical Oxidation ◽  
Chloride Ions ◽  
Physical Activation ◽  
Oh Radicals ◽  
Fenton Reagent ◽  
Chloranilic Acid ◽  
Promising Alternative ◽  
Toc Removal

AbstractIn this work, the degradation of chloranilic acid (CAA) by chemical oxidation with H2O2 alone and in the presence of ferrous iron Fe2+ catalyst was investigated in order to improve our understanding on the novel metal-independent approach. The interesting and efficient metal-independent hydroxyl radicals (OH) production by using halogenated quinones and H2O2 has been currently demonstrated. The results clearly confirmed the formation of OH radicals from the reaction of CAA with H2O2. CAA was slowly decayed by chemical oxidation with H2O2 and followed a pseudo-first kinetics. H2O2 doses ≥ 1000 mM were required to achieve complete CAA decay from 1 mM CAA. However, low total organic carbon (TOC) removal was measured with the accumulation of carboxylic acids. The addition of Fe2+ enhanced the kinetics of CAA degradation and reduced the required dose of H2O2. High TOC removal was obtained, almost complete release of chloride ions, without accumulation of carboxylic acids. The decolorization of methylene blue (MB) aqueous solutions was performed using H2O2, H2O2/CAA, H2O2/Fe2+, and H2O2/CAA/Fe2+. H2O2/CAA/Fe2+ was the most effective method in decolorizing MB solutions due to the accelerated Fe2+ regeneration. Coupling Fenton reagent with CAA seems to be promising alternative to physical activation in water and soil treatment.

Combination of advanced oxidation processes and gas absorption for the treatment of chlorinated solvents in waste gases

2001 ◽  
Vol 44 (9) ◽  
pp. 173-180 ◽  
Author(s):  
J. Dewulf ◽  
H. Van Langenhove ◽  
E. De Smedt ◽  
S. Geuens
Keyword(s):  
Advanced Oxidation Processes ◽  
Bubble Column ◽  
Chlorinated Solvents ◽  
Advanced Oxidation ◽  
Chemical Oxidation ◽  
Chloride Ions ◽  
Gas Absorption ◽  
Oh Radicals ◽  
Chlorinated Organic Compounds ◽  
Oxidation Processes

Treatment of chlorinated organic compounds in waste gases is difficult because of several reasons: these compounds are dioxin precursors when incinerated, and also biological treatment is difficult because of a limited number of suitable microbial degradation pathways. On the other hand, since the 1990s, a new generation of chemical oxidation techniques has been introduced in water treatment. Advanced Oxidation Processes (AOPs) are based on a combination of UV/H2O2, UV/O3 or H2O2/O3. The combinations result in the generation of OH-radicals, which subsequently attack the organic pollutants. In this work, the treatment of a gas stream (240 L/h) loaded with 20-40 ppmv trichloroethylene (TCE) is presented. Therefore, a combination of an absorption process in a bubble column with a liquid H2O2/O3 initiated oxidation, was investigated. Removal efficiencies, depending on the dosed H2O2 and O3, up to 94% were found. The production of chloride ions was investigated: the Cl-atoms from the removed TCE could be found back as chloride ions. Next to the experimental work, attention was paid to the mechanisms taking place in the proposed concept. Here, a simulation model was developed, considering gas/liquid mass transfer of TCE and ozone, axial liquid dispersion, advective gas and liquid transport and about 29 chemical reaction steps. The modelling allowed a better understanding of the technique and gives insight in its possibilities and limitations. Finally, it can be concluded that the proposed technique shows interesting perspectives: it is able to transform chlorine in chlorinated solvents into chloride ions effectively at ambient temperature conditions.

scholarly journals Oxidative Degradation of Tannic Acid in Aqueous Solution by UV/S2O82− and UV/H2O2/Fe2+ Processes: A Comparative Study

2019 ◽  
Vol 9 (1) ◽  
pp. 156 ◽  
Author(s):  
Sondos Dbira ◽  
Nasr Bensalah ◽  
Moustafa M. Zagho ◽  
Massouda Ennahaoui ◽  
Ahmed Bedoui
Keyword(s):  
Hydroxyl Radicals ◽  
Tannic Acid ◽  
Natural Waters ◽  
Oxidative Degradation ◽  
Complete Removal ◽  
Organic Pollution ◽  
Chemical Oxidation ◽  
Photocatalytic Decomposition ◽  
Fenton Process ◽  
Toc Removal

Tannic acid (TA) is a major pollutant present in the wastewater generated from vegetable tanneries process and food processing. This work studied TA degradation by two advanced oxidation processes (APOs): UV irradiation at the wavelength of 254 nm in the presence of hydrogen peroxide (H2O2) and ferrous iron (photo-Fenton) and in the presence of potassium persulfate. The influence of certain experimental parameters such as K2S2O8, H2O2, Fe2+, and TA concentrations, initial pH and temperature was evaluated in order to obtain the highest efficiency in terms of aromatics (decay in UV absorbance at 276 nm) and TOC removals. Chemical oxidation of TA (0.1 mM) by UV/persulfate achieved 96.32% of aromatics removal and 54.41% of TOC removal under optimized conditions of pH = 9 and 53.10 mM of K2S2O8 after 60 min. The treatment of TA by photo-Fenton process successfully led to almost complete aromatics removal (99.32%) and high TOC removal (94.27%) from aqueous solutions containing 0.1 mM of TA at natural pH = 3 using 29.4 mM of H2O2 and 0.18 mM of Fe2+ at 25 °C after 120 min. More efficient degradation of TA by photo-Fenton process than UV/persulfate was obtained, which confirms that hydroxyl radicals are more powerful oxidants than sulfate radicals. The complete removal of organic pollution from natural waters can be accomplished by direct chemical oxidation via hydroxyl radicals generated from photocatalytic decomposition of H2O2.

scholarly journals Killing of Bacillus Spores by Aqueous Dissolved Oxygen, Ascorbic Acid, and Copper Ions

2003 ◽  
Vol 69 (4) ◽  
pp. 2245-2252 ◽  
Author(s):  
J. B. Cross ◽  
R. P. Currier ◽  
D. J. Torraco ◽  
L. A. Vanderberg ◽  
G. L. Wagner ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Dissolved Oxygen ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Copper Ions ◽  
Transition Metal Ions ◽  
Fenton Reagent ◽  
Bacillus Spores ◽  
Modified Fenton

ABSTRACT An approach to decontamination of biological endospores is discussed. Specifically, the performance of an aqueous modified Fenton reagent is examined. A modified Fenton reagent formulation of cupric chloride, ascorbic acid, and sodium chloride is shown to be an effective sporicide under aerobic conditions. The traditional Fenton reaction involves the conversion of hydrogen peroxide to hydroxyl radical by aqueous ionic catalysts such as the transition metal ions. Our modified Fenton reaction involves the conversion of aqueous dissolved oxygen to hydrogen peroxide by an ionic catalyst (Cu2+) and then subsequent conversion to hydroxyl radicals. Results are given for the modified Fenton reagent deactivating spores of Bacillus globigii. A biocidal mechanism is proposed that is consistent with our experimental results and independently derived information found in the literature. This mechanism requires diffusion of relatively benign species into the interior of the spore, where dissolved O2 is then converted through a series of reactions which ultimately produce hydroxyl radicals that perform the killing action.

scholarly journals Hydroxyl-radical scavenging activity of hydrogen does not significantly contribute to its biological function

2021 ◽  
Author(s):  
Qinjian Li ◽  
Fei Xie ◽  
Yang Yi ◽  
Pengxiang Zhao ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Published Data ◽  
Oh Radicals ◽  
Dependent Manner ◽  
Protective Effects ◽  
Beneficial Effects ◽  
Wide Range ◽  
Depth Study

AbstractSince Ohsawa et al. reported a biological antioxidant function of hydrogen in 2007, researchers have now shown it to exert protective effects in a wide range of human and animal disease models. Clinical observations and scientific arguments suggest that a selective scavenging property of H2 cannot adequately explain the beneficial effects of hydrogen. However, there is no experiment challenging the original published data, which suggested that molecular hydrogen dissolved in solution reacts with hydroxyl radicals in cell-free systems. Here we report that a hydrogen-saturated solution (0.6 mM) did not significantly reduce hydroxyl radicals in the Fenton system using 1 mM H2O2. We replicated the same condition as Ohsawa’s study (i.e. 5 μM H2O2), and observed a decrease in •OH radicals in both the H2-rich and N2-rich solutions, which may be caused by a decreased dissolved oxygen concentration. Finally, we determined the effect of hydrogen on a high-valence iron enzyme, horseradish peroxidase (HRP), and found that hydrogen could directly increase HRP activity in a dose-dependent manner. Overall, these results indicate that although H2 and •OH can react, the reaction rate is too low to have physiological function. The target of hydrogen is more complex, and its interaction with enzymes or other macro-molecules deserve more attention and in-depth study.

scholarly journals Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: Uptake kinetics and condensed-phase products

2007 ◽  
Vol 7 (3) ◽  
pp. 6803-6842 ◽  
Author(s):  
I. J. George ◽  
A. Vlasenko ◽  
J. G. Slowik ◽  
J. P. D. Abbatt
Keyword(s):  
Hydroxyl Radicals ◽  
Particle Density ◽  
Organic Aerosols ◽  
Oxidation Products ◽  
Photochemical Oxidation ◽  
Mass Spectrometry Analysis ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Phase Reaction ◽  
Heterogeneous Oxidation

Abstract. The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gas-phase OH radicals were investigated under NOx-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl) sebacate (BES) particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS) and scanning mobility particle sizer (SMPS) was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O3 in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ0 = 1.26 (±0.04), confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

Atmospheric Chemistry of Perfluorinated Carboxylic Acids:  Reaction with OH Radicals and Atmospheric Lifetimes

2004 ◽  
Vol 108 (4) ◽  
pp. 615-620 ◽  
Author(s):  
M. D. Hurley ◽  
M. P. Sulbaek Andersen ◽  
T. J. Wallington ◽  
D. A. Ellis ◽  
J. W. Martin ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Atmospheric Chemistry ◽  
Oh Radicals ◽  
Perfluorinated Carboxylic Acids

scholarly journals Biogas production in the methane fermentation of excess sludge oxidized with Fenton’s reagent

2019 ◽  
Vol 116 ◽  
pp. 00104
Author(s):  
Iwona Zawieja ◽  
Kinga Brzeska
Keyword(s):  
Fermentation Process ◽  
Biogas Production ◽  
Process Conditions ◽  
Oh Radicals ◽  
Fenton’S Reagent ◽  
Iron Ions ◽  
Fenton Reagent ◽  
Excess Sludge ◽  
Methane Fermentation ◽  
Fenton's Reagent

The advanced oxidation processes (AOPs) play an important role in the degradation of hardly decomposable organic pollutants. AOPs methods rely on the production of highly reactive hydroxyl OH• radicals. The aim of the conducted research was to intensify biogas production in the methane fermentation process of excess sludge subjected to the process of deep oxidation with Fenton's reagent. In the process of oxidation of sewage sludge with the Fenton reagent, doses of iron ions in the range 0.02–0.14 g Fe2+/g TS (total solids) were used Hydrogen peroxide was measured in the proportions 1: 1–1:10 in relation to the mass of iron ions. The basic substrate of the study was excess sludge. In the case of excess sludge oxidation with the use of Fenton's reagent, the most favorable process conditions were considered to be the dose of iron ions 0.08 g Fe2+/g d.m. and a Fe2+: H2O2 ratio of 1:5. As a result of subjecting the excess sludge to disintegration with the Fenton reagent in the above-mentioned dose, with respect to the fermentation process of unprocessed sludge, about two-fold increase in the digestion degree of excess sludge and about 35% increase of the biogas yield was obtained.

scholarly journals Oxidative scission of plant cell wall polysaccharides by ascorbate-induced hydroxyl radicals

1998 ◽  
Vol 332 (2) ◽  
pp. 507-515 ◽  
Author(s):  
Stephen C. FRY
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Hydroxyl Radicals ◽  
Plant Cell Wall ◽  
Oh Radicals ◽  
Radical Scavengers ◽  
Cell Wall Polysaccharides ◽  
Ph Optimum ◽  
Living Plant

Scission of plant cell wall polysaccharides in vivo has generally been assumed to be enzymic. However, in the presence of l-ascorbate, such polysaccharides are shown to undergo non-enzymic scission under physiologically relevant conditions. Scission of xyloglucan by 1 mM ascorbate had a pH optimum of 4.5, and the maximum scission rate was reached after a 10–25-min delay. Catalase prevented the scission, whereas added H2O2 (0.1–10 mM) increased the scission rate and shortened the delay. Ascorbate caused detectable xyloglucan scission above approx. 5 µM. Dehydroascorbate was much less effective. Added Cu2+ (> 0.3 µM) also increased the rate of ascorbate-induced scission; EDTA was inhibitory. The rate of scission in the absence of added metals appeared to be attributable to the traces of Cu (2.8 mg·kg-1) present in the xyloglucan. Ascorbate-induced scission of xyloglucan was inhibited by radical scavengers; their effectiveness was proportional to their rate constants for reaction with hydroxyl radicals (•OH). It is proposed that ascorbate non-enzymically reduces O2 to H2O2, and Cu2+ to Cu+, and that H2O2 and Cu+ react to form •OH, which causes oxidative scission of polysaccharide chains. Evidence is reviewed to suggest that, in the wall of a living plant cell, Cu+ and H2O2 are formed by reactions involving ascorbate and its products, dehydroascorbate and oxalate. Systems may thus be in place to produce apoplastic •OH radicals in vivo. Although •OH radicals are often regarded as detrimental, they are so short-lived that they could act as site-specific oxidants targeted to play a useful role in loosening the cell wall, e.g. during cell expansion, fruit ripening and organ abscission.

scholarly journals Killing of Bacillus subtilis Spores by a Modified Fenton Reagent Containing CuCl2 and Ascorbic Acid

2004 ◽  
Vol 70 (4) ◽  
pp. 2535-2539 ◽  
Author(s):  
Michael P. Shapiro ◽  
Barbara Setlow ◽  
Peter Setlow
Keyword(s):  
Ascorbic Acid ◽  
Bacillus Subtilis ◽  
Acid Chloride ◽  
Chloride Ions ◽  
Fenton Reagent ◽  
Inner Membrane ◽  
Modified Fenton

ABSTRACT Bacillus subtilis spores were killed by CuCl2-ascorbic acid, chloride ions were essential for killing of spores, and spores with defective coats were killed more rapidly. CuCl2-ascorbic acid did not damage spore DNA, and spores killed by this reagent initiated germination. However, spores killed by CuCl2-ascorbic acid may have damage to their inner membrane.

scholarly journals Treatment of hazardous waste landfill leachate using Fenton oxidation process

2018 ◽  
Vol 34 ◽  
pp. 02034 ◽  
Author(s):  
Pradeep Kumar Singa ◽  
Mohamed Hasnain Isa ◽  
Yeek-Chia Ho ◽  
Jun-Wei Lim
Keyword(s):  
Reaction Time ◽  
Hazardous Waste ◽  
Landfill Leachate ◽  
Molar Ratio ◽  
Oh Radicals ◽  
Fenton Reagent ◽  
Leachate Treatment ◽  
Experimental Conditions ◽  
Waste Landfill ◽  
Hazardous Waste Landfill

The efficiency of Fenton’s oxidation was assessed in this study for hazardous waste landfill leachate treatment. The two major reagents, which are generally employed in Fenton’s process are H2O2 as oxidizing agent and Fe2+ as catalyst. Batch experiments were conducted to determine the effect of experimental conditions viz., reaction time, molar ratio, and Fenton reagent dosages, which are significant parameters that influence the degradation efficiencies of Fenton process were examined. It was found that under the favorable experimental conditions, maximum COD removal was 56.49%. The optimum experimental conditions were pH=3, H2O2/Fe2+ molar ratio = 3 and reaction time = 150 minutes. The optimal amount of hydrogen peroxide and iron were 0.12 mol/L and 0.04 mol/L respectively. High dosages of H2O2 and iron resulted in scavenging effects on OH• radicals and lowered degradation efficiency of organic compounds in the hazardous waste landfill leachate.

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