Simple and fast spectrophotometric determination of H2O2 in photo-Fenton reactions using metavanadate (original) (raw)
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Water Science and Technology, 2004
This study aims to investigate the effects of selected organic substances on the degradation of hydrogen peroxide during the Fenton reaction. Since the presence of organic substances can strongly affect the mechanism of the Fenton reaction, the information on effects of organic substances on the reaction would be a vital guide to the success of its application to the destruction of organics in wastewater. Several organic compounds having different structures were selected as model pollutants: 4-chlorophenol, 1,4-dioxane, chloroform, a dye (reactive black-5), and EDTA. Oxidation of 4-chlorophenol and reactive black-5 resulted in enormously fast degradation of hydrogen peroxide, while others such as 1,4-dioxane and chloroform showed much slower degradation. These experimental data were compared to simulation results from a computational model based on a simple áOH-driven oxidation model. Modelling results for chloroform and 1,4-dioxane were in relatively good agreement with the experi...
Revista de Chimie, 2008
An experimental study on 4-chlorophenol (4-CP) degradation in aqueous solutions by advanced oxidation process photo-Fenton type is presented. The efficiency of the oxidation process is determined by the very high oxidative potential of the OH. radicals generated by catalytic and photo-catalytic processes. The presence of the inorganic species inside the reaction medium influences the rate of the oxidation process as function of their nature and concentration. The inorganic anionic species reduce drastically the 4-CP oxidation efficiency by Fe2+/3+ complexing processes, HO. radicals scavenging effect or iron precipitate forming. The decrease of the 4-CP oxidation degree is correlated with the nature of the anions as following: Cl- ] PO43- ] SO42- ]] NO3-. The presence of the insoluble inorganic species (bentonite) modifies the oxidation efficiency by additional 4-CP and UV sorption processes, especially at high solution turbidity values.
Journal of pharmacognosy and phytochemistry, 2024
Introduction: Synthetic organic dyes are compounds that cannot be biologically degraded. This persistence is closely related to their chemical reactivity. If an organism has no specific mechanisms either to prevent resorption of a substance, or to eliminate it once it has been absorbed, then the substance accumulates. Methodology: The present study is limited to monitoring the decolorization of aqueous solutions of orange acid 10 molecules as a function of time. More specifically, it aims to compare the performance of the "Fenton" process and the "photo-Fenton" process with regard to the degradation of orange acid 10 molecules. The "Fenton" and "photo-Fenton" processes are based on the attack of synthetic organic dyes by oxidizing, non-selective radical entities known as "hydroxyl radicals". These radicals can be generated by "Fenton" reagents (iron cations Fe2+/hydrogen peroxide molecules H202), which have been extensively studied to remove organic matter from drinking water, explosives waste, industrial and agricultural waste, and polluted soil. Results: The results of our experiments lead us to conclude that the "photo-Fenton" process increases, albeit slightly, the degradation of orange acid 10 molecules compared to the "Fenton" process, irrespective of whether the medium is acidic, neutral or basic. Conclusion: These results are one way of overcoming the problems posed by synthetic organic dyes.
Photo-oxidative degradation of methyl orange in aqueous medium by Photo-Fenton reaction
2018
The present work evaluated the use of Photo-Fenton process for the oxidation (degradation) of Methyl Orange in an aqueous medium. The photo-Fenton best operating conditions, such as, irradiation time, dye concentration, H2O2/Fe dosage and the reaction kinetics were investigated and evaluated. The efficiency of the treatment was measured by the use of absorbance method using UV-Visible spectrophotometer. The results showed that the optimum irradiation time for the photo-Fenton process was equal REPORT Vol. 4, 2018 Science & Technology ISSN 2394–3750 EISSN 2394–3769
Chemical Oxidation by Photolytic Decomposition of Hydrogen Peroxide
Environmental Science & Technology, 1995
This paper describes a study of a chemical oxidation process involving simultaneous application of hydrogen peroxide solution and ultraviolet light (H20dUV) for removal of organic pollutants from aqueous solution. The process was investigated experimentally in a continuous-flow stirred tank reactor (CSTR) under various operational conditions, Le., H202 dosage, UV light intensity, and liquid residence time. Synthetic solutions of a model organic compound, n-chlorobutane (BuCI), were oxidized at various pH and in the presence of various amounts of humic material and carbonate/bicarbonate ions in order to examine the effect of water quality on the process efficiency. A kinetic model of the process, which was developed based on HzOdUV-induced radical oxidation of organic compounds, was successfully verified in pure water as well as in synthetic solutions.
Journal of Environmental Management, 2012
A highly concentrated aqueous saline-containing solution of phenol, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) was treated by the photo-Fenton process in a system composed of an annular reactor with a quartz immersion well and a medium-pressure mercury lamp (450 W). The study was conducted under special conditions to minimize the costs of acidification and neutralization, which are usual steps in this type of process. Photochemical reactions were carried out to investigate the influence of some process variables such as the initial concentration of Fe 2+ ([Fe 2+ ] 0 ) from 1.0 up to 2.5 mM, the rate in mmol of H 2 O 2 fed into the system (F H2O2, in ) from 3.67 up to 7.33 mmol of H 2 O 2 /min during 120 min of reaction time, and the initial pH (pH 0 ) from 3.0 up to 9.0 in the presence and absence of NaCl (60 g.L -1 ). Although the optimum pH for the photo-Fenton process is about 3.0, this particular system performed well in experimental conditions starting at alkaline and neutral pH. The results obtained here are promising for industrial applications, particularly in view of the high concentration of chloride, a known hydroxyl radical scavenger and the main oxidant present in photo-Fenton processes.
A review of classic Fenton's peroxidation as an advanced oxidation technique
Hydrogen peroxide (H 2 O 2) is a strong oxidant and its application in the treatment of various inorganic and organic pollutants is well established. Still H 2 O 2 alone is not effective for high concentrations of certain refractory contaminants because of low rates of reaction at reasonable H 2 O 2 concentrations. Improvements can be achieved by using transition metal salts (e.g. iron salts) or ozone and UV-light can activate H 2 O 2 to form hydroxyl radicals, which are strong oxidants. Oxidation processes utilising activation of H 2 O 2 by iron salts, classically referred to as Fenton's reagent is known to be very effective in the destruction of many hazardous organic pollutants in water. The first part of our paper presents a literature review of the various Fenton reagent reactions which constitute the overall kinetic scheme with all possible side reactions. It also sum-marises previous publications on the relationships between the dominant parameters (e.g. [H 2 O 2 ], [Fe 2+ ],. . .). The second part of our review discusses the possibility of improving sludge dewater-ability using Fenton's reagent.
Degradation of organic effluents containing wastewater by photo-Fenton oxidation process
RESEARCH STATEMENT TOPIC OF Ph.D THESIS : “USE OF PHOTOFENTONS REAGENT AS AN OXIDANT” YEAR OF SUBMITION : 2004 YEAR OF AWARD : 2006 PAPER PUBLICATION:02 (ONE NATIONAL AND ONE INTERNATIONAL LEVELIJC-A Vol.47A(11) [November 2008] Photooxidation of some organic pollutants (p-nitroaniline, p-aminophenols and acetanilide) has been carried out in the presence of photo-Fenton reagent. The effect of various parameters like pH, concentrations of organic compounds, ferric ions and hydrogen peroxide and light intensity, etc. on the reaction rate has been studied. The degradation is found to be pseudo first order. The optimum pHs for the degradation of p-aminophenol, p-nitroaniline and acetanilide are found to be 3.0, 3.5 and 2.5, respectively while the rate degradations of the three compounds are found to be comparable. The study shows that the photo-Fenton process are more effective and faster than Fenton's reagent in oxidation of organic compounds, and that the organic compounds are completely oxidized and degraded into CO2 and H2O. A tentative mechanism has been proposed. Excellent removal has been obtained using photo-Fenton process assisted with artificial irradiation. This study demonstrates that the use of photo-Fenton process on organic effluents wastewater treatment is very promising, especially when solar light is used.
Environmental Science & Technology, 2000
Orange II, the 4-(2-hydroxy-1-naphthylazo)benzenesulfonic acid Na-salt, was taken as a model for the oxidation of organic compounds in photoassisted Fenton process in the presence of Cl-anion in solution. The HO • radicals seem to originate due to the photolysis of Fe(OH) 2+ complexes in solution, whereas the Cl 2-• radical was a product of the photolysis of the FeCl 2+ complexes. The rate constants for the reaction of HO • and Cl 2-• radicals with Or II were determined by laser kinetic spectroscopy: k OH • +OrII) 6.0 × 10 9 (M s)-1 and k Cl2 • +OrII) 3.7 × 10 7 (M s)-1. A significant decrease in the rate of decoloration was observed for Orange II upon addition of Cl-(10 mM), but further addition of Clonly marginally affected the latter reaction rate. Chlorinated hydrocarbons are observed as the products of Orange II oxidation in photoassisted and dark Fenton processes in the presence of Clanions. Light irradiation was observed to decrease the amount of chlorinated organic products (AOX) in solution as compared to dark Fenton processes. The results obtained are shown to be in agreement with the radical reaction theory for the particular case of the Fenton reaction. Kinetic modeling of the Orange II decoloration was carried out taking into consideration the rate constants found for the reaction k HO • +OrII and k Cl2 • +OrII .
Journal of Photochemistry and Photobiology A: Chemistry, 2007
2,4-Dichlorophenoxyacetic acid (2,4-D) was degraded using both Fenton reagent and cobalt-peroxymonosulfate (Co/PMS) advanced oxidation processes (AOPs) in the dark and under solar radiation as source of light in photo-assisted AOPs. Four different concentrations of the transition metal (cobalt or Fe(II)) were tested maintaining constant the initial oxidant agent (PMS or hydrogen peroxide) concentration. The effect of temperature was investigated in the dark for both processes and the activation energy was determined for each process. For the processes performed in the dark, the maximum degradation for 2,4-D (86%) was achieved using Co/PMS (0.25 mmol L −1 of cobalt) in 48 min, while the dark Fenton achieved a maximum degradation of 2,4-D (17%) using 0.1 mmol L −1 of Fe(II). Complete 2,4-D degradation was achieved when the samples were irradiated by the sun using the same conditions described for 5 min of reaction time. In the case of solar-driven Co/PMS, complete 2,4-D degradation was achieved after 40 min using 0.004 mmol L −1 of cobalt. Pseudo first order reaction rate constants determined in the dark for Fe/H 2 O 2 and Co/PMS processes indicated that Co/PMS is able to perform the degradation of the pesticide at the same reaction rate as Fenton reagent, despite the fact that cobalt concentration is 100 times lower than Fe(II) concentration. Solar light increased the kinetic constant in the Co/PMS complex by 33 times compared with that obtained under dark conditions. Attempt to follow 2,4-D degradation using the photo-Fenton process was not possible since complete degradation occurred after the first 5 min of irradiation using [Fe] = 0.1 mmol L −1 .