scholarly journals Micropollutants as internal probe compounds to assess UV fluence and hydroxyl radical exposure in UV/H2O2 treatment

2021 ◽  
pp. 116940
Author(s):  
Robin Wünsch ◽  
Carina Mayer ◽  
Julia Plattner ◽  
Fabienne Eugster ◽  
Richard Wülser ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
H2o2 Treatment ◽  
Internal Probe

On a QSAR approach for the prediction of priority compound degradation by water treatment processes

2012 ◽  
Vol 66 (7) ◽  
pp. 1446-1453 ◽  
Author(s):  
B. A. Wols ◽  
D. Vries
Keyword(s):  
Water Treatment ◽  
Hydroxyl Radical ◽  
Chemical Property ◽  
Radical Reaction ◽  
Training Data ◽  
Quantitative Structure ◽  
H2o2 Treatment ◽  
Data Set ◽  
Physico Chemical ◽  
Physico Chemical Property

Emerging (chemical) substances are increasingly found in water sources and must be removed by water treatment systems. However, the treatment efficiency regarding these substances is often unknown. A promising approach is using QSARs (quantitative structure activity relationships) or QSPRs (quantitative structure property relationships) to correlate the existing knowledge of a compound's chemical structure to water treatment process properties, such as a biological activity or physico-chemical property. As UV/H2O2 treatment of water is an important barrier against priority pollutants, a QSAR model has been developed for the prediction of a typical physico-chemical property: i.e. hydroxyl radical reaction constants. Hydroxyl radicals are highly reactive and therefore largely responsible for a compound's degradation during UV/H2O2 treatment. A good correlation is found for the training data set. Chemical parameters that were related to charge on C atoms and topology of the compound were found to be important for the hydroxyl radical rate constants. So far, these results look promising, but further research is still required to increase the predictability of the model and to develop QSAR models for other physico-chemical properties.

UV/H2O2 treatment: an essential process in a multi barrier approach against trace chemical contaminants

2013 ◽  
Vol 13 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Joop C. Kruithof ◽  
Bram J. Martijn
Keyword(s):  
Water Treatment ◽  
Surface Water ◽  
Hydroxyl Radical ◽  
Endocrine Disrupting Compounds ◽  
Process Conditions ◽  
Acceptance Test ◽  
Reaction Products ◽  
H2o2 Treatment ◽  
Radical Oxidation ◽  
Surface Water Treatment

The presence of pesticides, endocrine disruptors and pharmaceuticals caused PWN to implement multiple barriers for organic contaminant control in their surface water treatment plants. A combination of advanced oxidation by UV/H2O2 treatment and granular activated carbon (GAC) filtration is installed. Medium pressure UV experiments in a standard pilot reactor have been carried out into the degradation of a representative selection of pesticides found in PWN's main raw water source, the IJssel Lake. It was observed that atrazine and diuron are more sensitive to direct photodegradation while bentazone and bromacil are primarily degraded by hydroxyl radical oxidation. Addition of H2O2 increased the decay rate of all selected herbicides. Using computational fluid dynamics, irradiance distribution and kinetic models developed by Trojan Technologies Inc., an optimized UV-reactor was designed. In tests with a pilot reactor according to this new design, the predicted performance was confirmed, both for photodegradation and hydroxyl radical oxidation. During the research period, the scope broadened from pesticides to pharmaceuticals, endocrine disrupting compounds, solvents and algae toxins. At process conditions 0.56 kWh/m3 and 6 mg/L H2O2, 80–100% degradation was achieved for compounds such as mecoprop, clofibric acid and diclofenac. A somewhat lower degradation was found for dicamba, 2, 4-D, bentazone, ibuprofen, carbamazepine and sulphametoxalol. The developed modelling was used to design a full scale UV/H2O2 system with an electric energy of 0.56 kWh/m3 for treatment of 3,000 m3/h. In a site acceptance test, degradation of atrazine was measured at two UV-doses at a fixed H2O2 dose of 6 mg/L. The installation performed as predicted by the design models and design criteria were met. At wtp Andijk, UV/H2O2 is integrated in the existing process train, preceded by conventional surface water treatment (coagulation, sedimentation and filtration) and followed by GAC filtration providing a robust barrier against reaction products from both oxidation and photolytic degradation (assimilable organic carbon, nitrite). Replacing the conventional pretreatment by ion exchange followed by ceramic microfiltration will further improve the economics of UV/H2O2 treatment.

Activation of cytochrome c to a peroxidase compound I-type intermediate by H2O2: relevance to redox signalling in apoptosis

2004 ◽  
Vol 71 ◽  
pp. 97-106 ◽  
Author(s):  
Mark Burkitt ◽  
Clare Jones ◽  
Andrew Lawrence ◽  
Peter Wardman
Keyword(s):  
Cytochrome C ◽  
Hydroxyl Radical ◽  
Redox Regulation ◽  
Chemotherapeutic Agents ◽  
Tyrosyl Radical ◽  
Compound I ◽  
Definitive Evidence ◽  
Enhanced Production ◽  
Physico Chemical

The release of cytochrome c from mitochondria during apoptosis results in the enhanced production of superoxide radicals, which are converted to H2O2 by Mn-superoxide dismutase. We have been concerned with the role of cytochrome c/H2O2 in the induction of oxidative stress during apoptosis. Our initial studies showed that cytochrome c is a potent catalyst of 2′,7′-dichlorofluorescin oxidation, thereby explaining the increased rate of production of the fluorophore 2′,7′-dichlorofluorescein in apoptotic cells. Although it has been speculated that the oxidizing species may be a ferryl-haem intermediate, no definitive evidence for the formation of such a species has been reported. Alternatively, it is possible that the hydroxyl radical may be generated, as seen in the reaction of certain iron chelates with H2O2. By examining the effects of radical scavengers on 2′,7′-dichlorofluorescin oxidation by cytochrome c/H2O2, together with complementary EPR studies, we have demonstrated that the hydroxyl radical is not generated. Our findings point, instead, to the formation of a peroxidase compound I species, with one oxidizing equivalent present as an oxo-ferryl haem intermediate and the other as the tyrosyl radical identified by Barr and colleagues [Barr, Gunther, Deterding, Tomer and Mason (1996) J. Biol. Chem. 271, 15498-15503]. Studies with spin traps indicated that the oxo-ferryl haem is the active oxidant. These findings provide a physico-chemical basis for the redox changes that occur during apoptosis. Excessive changes (possibly catalysed by cytochrome c) may have implications for the redox regulation of cell death, including the sensitivity of tumour cells to chemotherapeutic agents.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

1998 ◽  
Vol 38 (6) ◽  
pp. 147-154 ◽  
Author(s):  
Hideo Utsumi ◽  
Sang-Kuk Han ◽  
Kazuhiro Ichikawa
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Spin Trapping ◽  
Active Species ◽  
Generation Rate ◽  
Peak Height Ratio ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Phenol Derivatives ◽  
Semiquinone Radicals

Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

Heterogeneous Fenton Catalytic Removal of Organic Pollutant in Aqueous Solution by using Coal Gangue as a Catalyst

2019 ◽  
Vol 12 (4) ◽  
pp. 312-325
Author(s):  
Jiwei Zhang ◽  
Jingjing Xu ◽  
Shuaixia Liu ◽  
Baoxiang Gu ◽  
Feng Chen ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Removal Rate ◽  
Organic Pollutant ◽  
Coal Gangue ◽  
Ion Leakage ◽  
Heterogeneous Fenton ◽  
Solution Ph ◽  
X Ray

Background: Coal gangue was used as a catalyst in heterogeneous Fenton process for the degradation of azo dye and phenol. The influencing factors, such as solution pH gangue concentration and hydrogen peroxide dosage were investigated, and the reaction mechanism between coal gangue and hydrogen peroxide was also discussed. Methods: Experimental results showed that coal gangue has the ability to activate hydrogen peroxide to degrade environmental pollutants in aqueous solution. Under optimal conditions, after 60 minutes of treatment, more than 90.57% of reactive red dye was removed, and the removal efficiency of Chemical Oxygen Demand (COD) up to 72.83%. Results: Both hydroxyl radical and superoxide radical anion participated in the degradation of organic pollutant but hydroxyl radical predominated. Stability tests for coal gangue were also carried out via the continuous degradation experiment and ion leakage analysis. After five times continuous degradation, dye removal rate decreased slightly and the leached Fe was still at very low level (2.24-3.02 mg L-1). The results of Scanning Electron Microscope (SEM), energy dispersive X-Ray Spectrometer (EDS) and X-Ray Powder Diffraction (XRD) indicated that coal gangue catalyst is stable after five times continuous reuse. Conclusion: The progress in this research suggested that coal gangue is a potential nature catalyst for the efficient degradation of organic pollutant in water and wastewater via the Fenton reaction.

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