Oxidation of p-hydroxybenzoic acid by Fenton's reagent

Rivas, Javier; Beltrán, Fernando J.; Frades, J.; Buxeda, Paco

doi:10.1016/s0043-1354(00)00285-2

Cited by 206 publications

(107 citation statements)

References 23 publications

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“…p-hydroxybenzoic acid (p-HBA), o-HBA, m-HBA and other products such as ring fission and decarboxylation products (e.g. maleic and oxalic acids, cathecol and hydroquinone [19]). Moreover, the reaction between hydroxyl radicals and benzoic acid is known to require 5.87 ± 0.18 radicals moles to produce 1 mol p-HBA [20].…”

Section: Methods For Oxidative Radicals Detectionmentioning

confidence: 99%

“…Besides, organic acids such as maleic and oxalic acid, might scavenge Fe(III) during the process by forming stable complexes (e.g. ferrioxalate) which are not readily available to react with H 2 O 2 through Reaction (V) [19,25]. The above explanation would be true if only hydroxyl radicals were present in the Fenton's system.…”

Section: Measurement Of the Oxidative Radicals Total Amountmentioning

confidence: 99%

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Influence of the operating conditions on highly oxidative radicals generation in Fenton's systems

Ciotti

Baciocchi

Tuhkanen

2009

Journal of Hazardous Materials

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a b s t r a c tIn this work, an indirect method for estimating the total amount and concentration of oxidative radicals in aqueous and slurry-phase Fenton's systems was developed. This method, based on the use of benzoic acid as probe compound, was applied for evaluating the effect of the operating conditions on the radicals amount produced, their production efficiency (i.e. moles of radicals generated per mole H 2 O 2 ) and their concentration. A Rotatable Central Composite design (RCC) was used to select the operating conditions in order to get a statistically meaningful data set. Hydrogen peroxide and ferrous ion concentrations ranged between 0.2-1 mM and 0.2-0.5 mM, respectively; humic acid concentration between 0 and 15 mg/L, whereas the soil/water weight ratio in slurry-phase systems between 1:10 and 9:10. The probe compound concentration was 9 or 0.1 mM in experiments aimed to evaluate the total amount or concentration of oxidative radicals, respectively. The obtained results indicated that the amount of radicals generated in both aqueous and soil slurry Fenton's system increased with higher H 2 O 2 concentration and, more specifically, that their production efficiency increased with increasing Fe(II):H 2 O 2 molar ratio. Addition of dissolved organic compounds as humic acid did not notably affect the oxidative radicals amount and concentration. On the contrary, a one order of magnitude reduction in both radicals amount generated and concentration was observed when soil was added to the reaction environment.

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Section: Methods For Oxidative Radicals Detectionmentioning

confidence: 99%

Section: Measurement Of the Oxidative Radicals Total Amountmentioning

confidence: 99%

Influence of the operating conditions on highly oxidative radicals generation in Fenton's systems

Ciotti

Baciocchi

Tuhkanen

2009

Journal of Hazardous Materials

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“…The effect of oxalate on hydroxyl radical formation in cultures was measured by hydroxylation of p-hydroxybenzoic acid to form protocatechuic acid (41). Increasing the concentration of oxalate added to high-carbon, low-nitrogen cultures resulted in decreased protocatechuic acid formation (Fig.…”

Section: Reduction Of Iron By 25-dmhqmentioning

confidence: 99%

Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation

Varela

Tien

2003

Appl Environ Microbiol

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The redox cycle of 2,5-dimethoxybenzoquinone (2,5-DMBQ) is proposed as a source of reducing equivalent for the regeneration of Fe 2؉ and H 2 O 2 in brown rot fungal decay of wood. Oxalate has also been proposed to be the physiological iron reductant. We characterized the effect of pH and oxalate on the 2,5-DMBQ-driven Fenton chemistry and on Fe 3؉ reduction and oxidation. Hydroxyl radical formation was assessed by lipid peroxidation. We found that hydroquinone (2,5-DMHQ) is very stable in the absence of iron at pH 2 to 4, the pH of degraded wood. . Catalase and hydroxyl radical scavengers were effective inhibitors of lipid peroxidation, whereas superoxide dismutase caused no inhibition. At a low concentration of oxalate (50 M), ferric ion reduction and lipid peroxidation are enhanced. Thus, the enhancement of both ferric ion reduction and lipid peroxidation may be due to oxalate increasing the solubility of the ferric ion. Increasing the oxalate concentration such that the oxalate/ferric ion ratio favored formation of the 2:1 and 3:1 complexes resulted in inhibition of iron reduction and lipid peroxidation. Our results confirm that hydroxyl radical formation occurs via the 2,5-DMBQ redox cycle.A prerequisite to gaining access to the cellulose and hemicellulose components of woody biomass is the circumvention of the lignin barrier. Filamentous fungi, the predominant degraders of wood, have evolved at least two mechanisms to circumvent this barrier. White rot fungi circumvent the lignin barrier by degrading it with extracellular peroxidases (14, 47), with eventual degradation to the level of CO 2 (28). In contrast, brown rot fungi cannot degrade the lignin component to CO 2 . However, these fungi can access the cellulose components with minimal modification of the lignin. These modifications include demethylation of aryl methoxy groups and ring hydroxylation (for a more extensive review, see reference 29).Due to the limited size of the wood pores and the nonspecific nature of wood degradation, Cowling and Brown (12) suggested that low-molecular-weight oxidants are the initial agents in wood decay. Koenigs (33) showed that a number of wood-decomposing fungi produce H 2 O 2 and noted the similarities between wood treated with the hydroxyl radical and with brown rot fungi (34). Illman et al. (23) subsequently detected the hydroxyl radical in incubations with the brown rot fungus Poria placenta by use of electron spin resonance and spin trapping agents. Further supporting the involvement of the hydroxyl radical is the formation of 3-hydroxy derivatives (the expected products from a hydroxyl radical attack) of phthalic hydrazide in incubations with brown rot fungi (5).The most likely nonphotochemical source of the hydroxyl radical is Fenton's reagent, defined by the following chemistry: The quinone undergoes cyclic oxidation-reduction reactions, serving as a shuttle for electrons from intracellular donors to extracellular acceptors. Although a similar mechanism has been proposed for white rot fungi (4, 17, 18) for h...

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“…The H2O2 is almost always the limiting agent; moreover, during the process, the Fe 2+ can be regenerated by the action of light (see reaction (11)), and act as a catalyst, while the H2O2 must be sufficiently high to generate hydroxyl radicals [39]. pH and consequently, an increased generation of HO.…”

Section: +mentioning

confidence: 99%

A Study of Photocatalytic Processes Involving the Degradation of the Organic Load and Amoxicillin in Hospital Wastewater

Martins¹,

Mayer

Confortin

et al. 2009

CLEAN Soil Air Water

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An investigation was carried out into the treatment of wastewater from the University Hospital of Santa Maria (HUSM) by means of a heterogeneous photocatalytic process (HPP) and a photo-Fenton process (PFP) using Response Surface Methodology (RSM) for maximizing the removal efficiency of the chemical oxygen demand, COD. The rates of COD reduction obtained by HPP and PFP were 44 and 64.6%, respectively. The toxicity (LC 50 values) of the hospital wastewater (pre-and post-treatment) were determined by means of the bioassay Artemia salina. During the treatment a toxicity inhibition of 43.5% was achieved by photo-Fenton and 46.3% by TiO 2 photocatalysis. Spiked samples of hospital effluent with amoxicillin were degraded by 100% after treatment by HPP for 30 min and 85% after treatment by PFP for 60 min, as measured by high performance liquid chromatography (HPLC). All the treatments were conducted on a bench scale using a batch recirculation 2 L Dewar-like photoreactor provided with a light intensity of 401 W/m 2 , which was irradiated by a 125 W medium pressure mercury vapor lamp. Ferrioxalate actinometry solution was used to measure the photon flux (q = 1.71 N 10 -5 l 1.25 N 10 -7). The photonic efficiency was 30.00 l 0.67% for PFP and 19.02 l 0.88% for HPP.

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Oxidation of p-hydroxybenzoic acid by Fenton's reagent

Cited by 206 publications

References 23 publications

Influence of the operating conditions on highly oxidative radicals generation in Fenton's systems

Influence of the operating conditions on highly oxidative radicals generation in Fenton's systems

Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation

A Study of Photocatalytic Processes Involving the Degradation of the Organic Load and Amoxicillin in Hospital Wastewater

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