Advanced oxidation processes: mechanistic aspects

2008 ◽  
Vol 58 (5) ◽  
pp. 1015-1021 ◽  
Author(s):  
C. von Sonntag
Keyword(s):  
Activated Carbon ◽  
Fenton Reaction ◽  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
Oh Radicals ◽  
Oh Radical ◽  
Reactive Intermediate ◽  
Oxidation Processes ◽  
Water Matrix ◽  
Vacuum Uv

The reactive intermediate in Advanced Oxidation Processes (AOPs) is the •OH radical. It may be generated by various approaches such as the Fenton reaction (Fe2 + /H2O2), photo-Fenton reaction (Fe3 + /H2O2/hν), UV/H2O2, peroxone reaction (O3/H2O2), O3/UV, O3/activated carbon, O3/dissolved organic carbon (DOC) of water matrix, ionizing radiation, vacuum UV, and ultrasound. The underlying reactions and •OH formation efficiencies are discussed. The key reactions of •OH radicals also addressed in this review.

scholarly journals Ultrafine bubbles as an augmenting agent for ozone-based advanced oxidation

2021 ◽  
Author(s):  
Tatek Temesgen ◽  
Mooyoung Han
Keyword(s):  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
Negative Influence ◽  
Oh Radicals ◽  
Oh Radical ◽  
Oxidation Processes ◽  
Acidic Conditions ◽  
Ph Conditions ◽  
First Time ◽  
Influence Of Ph

Abstract In this study, the influence of nanobubbles (NBs) application in ozone (O3) based advanced oxidation processes (AOP) is investigated. The results demonstrate the potential of NBs application to O3 – based AOP. It was observed that NBs suppress the negative influence of pH and operating temperatures on the efficiency of ozonation. In addition, the application of NBs tends to improve the solubility of O3 and the rate of mass transfer under the influence of a broad range of temperature and pH conditions. The results of this research indicate that application of NBs minimized the reduction in concentration of dissolved O3 with an increase in temperature. Furthermore, application of NBs highly improved the OH radical formation in acidic conditions. The results of this research depicted for first time that the application of NBs strongly encourages the initiation of reactions involving OH radicals. It was found by this research that NBs can boost the concentration of OH radicals up to 3.5 fold compared to equivalent MB supported ozonation systems. This is assumed to improve the efficiency of currently existing conventional bubble supported O3 – based AOP systems.

Inter-calibration of OH radical sources and water quality parameters

1997 ◽  
Vol 35 (4) ◽  
pp. 1-8 ◽  
Author(s):  
Jürg Hoigné
Keyword(s):  
Water Quality ◽  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
Quality Parameters ◽  
Water Quality Parameters ◽  
Oh Radicals ◽  
Oh Radical ◽  
Natural Systems ◽  
Oxidation Processes

OH radicals are the key oxidants that control most Advanced Oxidation Processes (AOPs) currently applied in water technology and that also occur in some natural systems such as cloud waters. The efficiencies of the various OH radical sources can be experimentally quantified and compared when they are calibrated by following the oxidation of inter-calibrated reference compounds that react during the process only with OH radicals. To apply and generalize the results, however, water quality parameters controlling the lifetime of OH radicals via OH-scavenging reactions by pollutants and further solutes must also be quantified by methods that allow for calibrations.

The basics of oxidants in water treatment. Part A: OH radical reactions

2007 ◽  
Vol 55 (12) ◽  
pp. 19-23 ◽  
Author(s):  
C. von Sonntag
Keyword(s):  
Water Treatment ◽  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
Radical Reactions ◽  
Oh Radicals ◽  
Oh Radical ◽  
Oxidation Processes

The Advanced Oxidation Processes (AOPs) are based on the reactions of the highly reactive •OH radicals. The formation of •OH by the various AOPs and their ensuing reactions are reviewed.

scholarly journals Metal-Free Fenton-like Photocatalysts Based on Covalent Organic Frameworks

2021 ◽  
Author(s):  
Qiaobo Liao ◽  
Can Ke ◽  
Dongni Wang ◽  
Yiying Zhang ◽  
Qingwen Han ◽  
...  
Keyword(s):  
Fenton Reaction ◽  
High Stability ◽  
Advanced Oxidation Processes ◽  
Superoxide Radical ◽  
Advanced Oxidation ◽  
Oxygen Species ◽  
Oxidation Processes ◽  
Metal Free ◽  
Layer Stacking ◽  
Opening Up

The Fenton reaction is one of the most efficient and widely used advanced oxidation processes for remediating the ever-growing water pollution. Metal-free photocatalysts for Fenton-like reactions have gathered enormous scientific interest for their advantages including board pH operation range and high stability. Herein, we demonstrate a metal-free covalent organic framework (COF)-based standalone photocatalyst with superior reactivity and reusability for Fenton-like reactions at acid and neutral pH solutions, which can be attributed to its large porosity, high density of the photoactive triazine moiety, vertical π arrays formed by eclipsed layer stacking and the <i>β</i>‑ketoenamine linkage. Our experiments showed that the photocatalyst can absorb visible light effectively for activation of H<sub>2</sub>O<sub>2</sub>, producing abundant reactive oxygen species including superoxide radical (O<sub>2</sub><sup>·-</sup>), hydroxyl radical (<sup>·</sup>OH), and singlet oxygen (<sup>1</sup>O<sub>2</sub>) for oxidizing organic pollutants. This work not only provides an efficient metal-free photocatalyst for Fenton-like reactions, but also paves the way for COFs towards advanced oxidation processes, opening up the possibilities to their future applications in industry.

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.

Treatment Performance of Low Strength Electric Wastewater Using Solid-Advanced Oxidation Processes

2012 ◽  
Vol 724 ◽  
pp. 29-32
Author(s):  
Jong Oh Kim ◽  
Jun Su Lee ◽  
Jin Wook Chung
Keyword(s):  
Activated Carbon ◽  
Advanced Oxidation Processes ◽  
Isopropyl Alcohol ◽  
Advanced Oxidation ◽  
Low Molecular Weight ◽  
Mixing Ratio ◽  
Acetone Concentration ◽  
Oxidation Processes ◽  
Treatment Performance ◽  
Catalyst Effect

This study aims to show the catalyst effect for the removal of low molecular weight organics in semiconductor wastewater. To investigate and compare the removal efficiency, experiments were conducted to change in mixing ratio of catalyst with activated carbon. As a result, optimal condition for the removal of acetone and IPA of the catalyst ratio was (Cu+Fe) = 8:2 and (Fe+Al)=9:1 with activated carbon at pH 3. Acetone was removed above 70% and isopropyl alcohol (IPA) was almost removed 100% in the pH 3, pH 4 except for pH 7 condition, the remaining acetone concentration was 51.4 ppb in IPA solution, these results is attributed that IPA transformed to acetone after the reaction. Solid-advanced oxidation processes was believed to be an effective method to treat the low adsorbability of organics contained in electric wastewater.

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