Evidence for superoxide-radical anion, singlet oxygen and OH-radical intervention during the degradation of the lignin model compound (3-methoxy-4-hydroxyphenylmethylcarbinol)

Raja, P.; Bozzi, Anna; Mansilla, Héctor D.; Kiwi, J.

doi:10.1016/j.jphotochem.2004.07.009

Cited by 106 publications

(61 citation statements)

References 15 publications

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“…As mentioned in the literature, the O 2 ·− attacks preferentially aromatic rings with low electronic density (Palominos et al 2008) (as deactivated aromatic rings in chlorophenols). The participation of O 2 ·− has been reported to be involved in several oxidation mechanisms of organic compounds (Palominos et al 2008;Raja et al 2005), including PCP during the photocatalytic process (Yin et al 2010;Li et al 2011). In fact, it is well known that one electron oxidation of phenolic compounds leads to the formation of phenoxyl radicals which undergo ring-opening reactions in the presence of O 2 ·− (Raja et al 2005).…”

Section: Contribution Of Reactive Species To the Photocatalytic Degramentioning

confidence: 99%

“…The participation of O 2 ·− has been reported to be involved in several oxidation mechanisms of organic compounds (Palominos et al 2008;Raja et al 2005), including PCP during the photocatalytic process (Yin et al 2010;Li et al 2011). In fact, it is well known that one electron oxidation of phenolic compounds leads to the formation of phenoxyl radicals which undergo ring-opening reactions in the presence of O 2 ·− (Raja et al 2005). The photocatalytic degradation of PCP was further investigated in the absence of oxygen under nitrogen gas bubbling, and the rate constants obtained were 0.3×10 −2 and 0.5×10 −2 min -1 for pH 4 and 10, respectively.…”

Section: Contribution Of Reactive Species To the Photocatalytic Degramentioning

confidence: 99%

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Photocatalytic degradation of pentachlorophenol by visible light Ν–F–TiO2 in the presence of oxalate ions: optimization, modeling, and scavenging studies

Αντωνοπούλου

Konstantinou

2015

Environ Sci Pollut Res

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The efficiency of heterogeneous photocatalysis using N-F-TiO2 as photocatalyst to degrade a priority pollutant, pentachlorophenol (PCP), in the presence of oxalates (OA) was investigated in detail. Response surface methodology was used to optimize the effect of three variables (catalyst concentration, OA/PCP ratio, and pH) on the photocatalytic degradation of pentachlorophenol. A quadratic model was established as a functional relationship between three independent variables and the degradation efficiency of PCP. The results of model fitting and statistical analysis demonstrated that the pH played a key role in the degradation of PCP. Within the studied experimental ranges, the optimum conditions for maximum PCP degradation efficiency (97.5 %) were: catalyst concentration 600 mg L(-1), OA/PCP ratio 2, and pH 10. The contribution of HO(·), O2 (·-), and e(-) produced during the photocatalytic treatment was investigated with the addition of scavengers. The photocatalytic degradation was essentially proceeded through an oxidative mechanism at both acid and alkaline pH values by HO(.) and O2 (·-) radicals attack. It was found that O2 (·-) were the major reactive species involved in PCP degradation in pH 4 and HO(·) in pH 10.

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Section: Contribution Of Reactive Species To the Photocatalytic Degramentioning

confidence: 99%

Section: Contribution Of Reactive Species To the Photocatalytic Degramentioning

confidence: 99%

Photocatalytic degradation of pentachlorophenol by visible light Ν–F–TiO2 in the presence of oxalate ions: optimization, modeling, and scavenging studies

Αντωνοπούλου

Konstantinou

2015

Environ Sci Pollut Res

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“…In addition, benzoquinone (BQ) can be used to detect the superoxide anion (O 2 −• ) due to their ability to trap this anion radical by an electron transfer mechanism (BQ þ O 2 À ! BQ À þ O 2 ) (Palominos et al 2009;Raja et al 2005). Hence, EDTA and BQ were used to .…”

Section: Degradation Rate Of Pcb3 As Affected By Radicals and Hole Inmentioning

confidence: 99%

TiO2 photocatalytic degradation of 4-chlorobiphenyl as affected by solvents and surfactants

et al. 2012

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Purpose TiO 2 photocatalytic degradation of 4-chlorobiphenyl (PCB3) in aqueous solution under UV irradiation was investigated as affected by different environmental factors, including initial PCB3 concentration, TiO 2 content, UV intensity, H 2 O 2 concentration, cosolvents, and surfactants. Materials and methods The solution of PCB3 with TiO 2 was irradiated by medium mercury lamp. The concentration of PCB3 and intermediates was analyzed by GC-μECD and GC-MS. The values of point charge and bond length were also calculated with ChemOffice 2004 (Mopac unit). Results and discussion Photocatalysis was very effective for PCB3 removal, and the degradation kinetics were fitted with a pseudo-first order reaction model. PCB3 was efficiently degraded in the presence of acetone and acetonitrile, but was completely inhibited with other examined cosolvents. HPCD and Tween80 also inhibited the degradation rate of PCB3, while Brij35 slightly decreased the degradation rate of PCB3 at first, and then increased. The reaction mechanism occurred principally by hydroxyl radicals involving the participation of holes and superoxide anion oxidation.A possible photocatalytic degradation pathway of PCB3 was proposed based on the identified reaction intermediates as well as computer simulation. Conclusions The photocatalytic approach could be successfully applied to degrade PCB3, and cosolvents and surfactants significantly influenced its degradation kinetics.

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“…A similar procedure to study the influence of common occur-ring ions (Cl − , SO4 2− , NO3 − , NH4 + , PO4 3− ; 1 g L −1 and HCO3 − ; 0.1 g L −1 ) in various types of wastewaters (Boaventura et al 1997;Vilar et al 2009;Sousa et al 2012) and the formation of different reactive species, hydroxyl radical, and singlet oxygen, using selective scavengers (50 mM of D-mannitol and 10 mM NaN3, respectively; Hirakawa et al 2004;Raja et al 2005), was carried out in the lab-scale apparatus. The recirculation glass vessel of the lab-scale prototype was filled with 1 L of 20 mg L −1 AMX solution, which was pumped to the CPC unit (Vi=270 mL, Vi/Vt=0.27, ti=0.43 min, tdark=1.16 min, ACPC= 0.023 m 2 ) and homogenized by recirculation in the closed system during 15 min in the dark.…”

Section: Lab-scale Photoreactormentioning

confidence: 99%

Assessment of solar driven TiO2-assisted photocatalysis efficiency on amoxicillin degradation

Pereira

Reis

Nunes

et al. 2013

Environ Sci Pollut Res

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The objective of this work was to evaluate the efficiency of a solar TiO2-assisted photocatalytic process on amoxicillin (AMX) degradation, an antibiotic widely used in human and veterinary medicine. Firstly, solar photolysis of AMX was compared with solar photocatalysis in a compound parabolic collectors pilot scale photoreactor to assess the amount of accumulated UV energy in the system (QUV) necessary to remove 20 mg L −1 AMX from aqueous solution and mineralize the intermediary byproducts. Another experiment was also carried out to accurately follow the antibacterial activity against Escherichia coli DSM 1103 and Staphylococcus aureus DSM 1104 and mineralization of AMX by tracing the contents of dissolved organic carbon (DOC), low molecular weight carboxylate anions, and inorganic anions. Finally, the influence of individual inorganic ions on AMX photocatalytic degradation efficiency and the involvement of some reactive oxygen species were also assessed. Photolysis was shown to be completely ineffective, while only 3.1 kJUVL −1 was sufficient to fully degrade 20 mg L −1 AMX and remove 61 % of initial DOC content in the presence of the photocatalyst and sunlight. In the experiment with an initial AMX concentration of 2 40 mg L −1 , antibacterial activity of the solution was considerably reduced after elimination of AMX to levels below the respective detection limit. After 11.7 kJUVL −1 , DOC decreased by 71 %; 30 % of the AMX nitrogen was converted into ammonium and all sulfur compounds were converted into sulfate. A large percentage of the remaining DOC was in the form of low molecular weight carboxylic acids. Presence of phosphate ions promoted the removal of AMX from solution, while no sizeable effects on the kinetics were found for other inorganic ions. Although the AMX degradation was mainly attributed to hydroxyl radicals, singlet oxygen also plays an important role in AMX self-photosensitization under UV/ visible solar light.

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Evidence for superoxide-radical anion, singlet oxygen and OH-radical intervention during the degradation of the lignin model compound (3-methoxy-4-hydroxyphenylmethylcarbinol)

Cited by 106 publications

References 15 publications

Photocatalytic degradation of pentachlorophenol by visible light Ν–F–TiO2 in the presence of oxalate ions: optimization, modeling, and scavenging studies

Photocatalytic degradation of pentachlorophenol by visible light Ν–F–TiO2 in the presence of oxalate ions: optimization, modeling, and scavenging studies

TiO2 photocatalytic degradation of 4-chlorobiphenyl as affected by solvents and surfactants

Assessment of solar driven TiO2-assisted photocatalysis efficiency on amoxicillin degradation

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