scholarly journals Feasibility Study of Tetracycline Removal by Ozonation Equipped with an Ultrafine-Bubble Compressor

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1058
Author(s):  
Chikang Wang ◽  
Chien-Yu Lin ◽  
Guan-Yun Liao
Keyword(s):  
Cell Viability ◽  
Organic Compounds ◽  
Feasibility Study ◽  
Oxidation Mechanism ◽  
Oh Radicals ◽  
Oh Radical ◽  
Operational Cost ◽  
Reaction Parameters ◽  
Radical Oxidation ◽  
Animal Care

In this study, a combination of an ozone gas producer and an ultrafine-bubble compressor was used to degrade tetracycline, which is a well-known antibiotic and medicine commonly used in human and animal care, and effects of varying the reaction parameters were studied. Experiments indicate that each gram of introducing ozone can degrade 2.72 g of tetracycline at pH 3 and 1.48 g at pH 11. However, basic conditions contribute to increased mineralization of tetracycline because of the ·OH radical oxidation mechanism. Higher reaction temperatures and higher ozone dosages enhance the reactivity between the ozone molecules, ·OH radicals, and tetracycline, resulting in a decline in the toxicity of the tetracycline solution as measured by cell viability. The mineralization of organic compounds is the key to decreasing the toxicity of the solution. Ultrafine-bubble ozonation can provide homogeneity of gas bubbles in solution hence it not only reduces the requirement of ozone and thus the operational cost of the reaction, but also extends the efficacy of the method to the treatment of solutions with high tetracycline concentrations.

Atmospheric oxidation mechanism of polyfluorinated sulfonamides — A quantum chemical and kinetic study

2013 ◽  
Vol 91 (6) ◽  
pp. 472-478 ◽  
Author(s):  
Xiaoyan Sun ◽  
Lei Ding ◽  
Qingzhu Zhang ◽  
Wenxing Wang
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Single Point ◽  
Oxidation Mechanism ◽  
Basis Set ◽  
Atmospheric Oxidation ◽  
Oh Radicals ◽  
Oh Radical ◽  
Orbital Theory ◽  
Point Energy

Polyfluorinated sulfonamides (FSAs, F(CF2)nSO2NR1R2) are present in the atmosphere and may serve as the source of perfluorocarboxylates (PFCAs, CF3(CF2)nCOO–) in remote locations through long-range atmospheric transport and oxidation. Density functional theory (DFT) molecular orbital theory calculations were carried out to investigate OH radical-initiated atmospheric oxidation of a series of sulfonamides, F(CF2)nSO2NR1R2 (n = 4, 6, 8). Geometry optimizations of the reactants as well as the intermediates, transition states, and products were performed at the MPWB1K level with the 6-31G+(d,p) basis set. Single-point energy calculations were carried out at the MPWB1K/6-311+G(3df,2p) level of theory. The OH radical-initiated reaction mechanism is given and confirms that the OH addition to the sulfone double bond producing perfluoroalkanesulfonic acid directly cannot occur in the general atmosphere. Canonical variational transition-state (CVT) theory with small curvature tunneling (SCT) contribution was used to predict the rate constants. The overall rate constants were determined, k(T) (N-EtFBSA + OH) = (3.21 × 10−12) exp(–584.19/T), k(T) (N-EtFHxSA + OH) = (3.21 × 10−12) exp(–543.24/T), and k(T) (N-EtFOSA + OH) = (2.17 × 10−12) exp(–504.96/T) cm3 molecule−1 s−1, over the possible atmospheric temperature range of 180–370 K, indicating that the length of the F(CF2)n group has no large effect on the reactivity of FSAs. Results show that the atmospheric lifetime of FSAs determined by OH radicals will be 20–40 days, which agrees well with the experimental values (20–50 days), 20 thus they may contribute to the burden of perfluorinated pollution in remote regions.

scholarly journals Removal of Pb (II) Ions in The Aqueous Solution by Photo-Fenton Method

2019 ◽  
Vol 21 (2) ◽  
pp. 180-186 ◽  
Keyword(s):  
Aqueous Solution ◽  
Reaction Time ◽  
Uv Light ◽  
Irradiation Time ◽  
Oxidation Mechanism ◽  
Operating Parameters ◽  
Oh Radicals ◽  
Oh Radical ◽  
Fenton Process ◽  
Batch Technique

<p>Photo-Fenton for decreasing concentration of Pb(II) ions in the aqueous solution is systematically studied. The photo-Fenton process was carried out by batch technique, under UV light. The influences of process operating parameters were evaluated. The results of the research demonstrated that by photo-Fenton process, the concentration of Pb(II) ions in the aqueous solution can be decreased, that may be through oxidation mechanism by OH radicals. The decrease is found to be controlled by Fe2+ and H2O2 concentrations, as well as by the pH and the irradiation time. For 20 mg/L of Pb(II) in the 100 mL solution, the optimum condition of the oxidation is obtained to be 10 mmole/L of Fe2+, 200 mmole/L of H2O2, pH 3, and 90 min of the reaction time. It is also confirmed that the oxidation of Pb (II) by OH radical has formed the undissolved PbO2, that is less toxic and easier to be handled.</p>

The atmospheric oxidation mechanism and kinetics of 1,3,5-trimethylbenzene initiated by OH radicals – a theoretical study

2017 ◽  
Vol 41 (18) ◽  
pp. 10259-10271 ◽  
Author(s):  
S. Ponnusamy ◽  
L. Sandhiya ◽  
K. Senthilkumar
Keyword(s):  
Theoretical Study ◽  
Oxidation Mechanism ◽  
Peroxy Radical ◽  
Ring Closure ◽  
Oh Radicals ◽  
Oh Radical ◽  
Radical Ring ◽  
Atmospheric Fate ◽  
Mechanism And Kinetics ◽  
Kinetics Of

The atmospheric fate of 1,3,5-trimethylbenzene is determined by OH-radical addition, and subsequent bicyclic peroxy radical ring closure and ring breaking pathways.

A new analytical method, using the dark Fenton reaction as an OH radical source to study oxidations of unsaturated (di)aldehydes in the aqueous phase

2021 ◽  
Author(s):  
Majda Mekic ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Organic Compounds ◽  
Aqueous Phase ◽  
Phase Transfer ◽  
Catalytic Decomposition ◽  
Water Soluble ◽  
Radical Scavenger ◽  
Oh Radicals ◽  
Oh Radical ◽  
Fenton Chemistry ◽  
Typical Experiment

&lt;p&gt;Anthropogenic and biogenic sources produce numerous primary emitted gases, organic compounds, and aerosols in the atmosphere. An important group of such compounds are &amp;#945;, &amp;#946;-unsaturated carbonyl molecules, which can be formed in the atmosphere due to their secondary origin, including oxidation of their precursors such as hydrocarbons with common atmospheric oxidants such as hydroxyl radicals (&amp;#8231;OH). Since those compounds contain at least one double bond and one carbonyl group, they are characterized as water-soluble molecules, which can diffuse on the cloud droplets&amp;#8217; surface and undergo a phase transfer from the gas phase to the atmospheric aqueous phase. In the latter, the oxidized organic compounds can contribute to aerosol mass production through in-cloud processes, yielding aqueous phase secondary organic aerosols (aqSOA). Due to their strong photochemical behavior, the development of a new analytical approach for evaluating the OH radical kinetics in the aqueous phase under dark conditions was essential. One of the most studied non-photolytic reactions is Fenton chemistry (Fe(II)/H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;), which serves as an OH radical source in the dark in the atmospheric aqueous phase after catalytic decomposition of H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; in the presence of Fe(II) at acidic pH values. In a typical experiment, temperature-dependent second-order rate constants of OH radicals with unsaturated dialdehydes, such as (1) crotonaldehyde, and (2) 1,4-butenedial, were determined in a bulk reactor by using the competition kinetics method. In the newly developed method, the role of radical scavenger was performed by isotopically labeled 2-propanol (d8), while the OH-initiated oxidation produces deuterated acetone (d6), being analyzed with GC-MS after derivatization. The findings from our research will be incorporated in the CAPRAM model to explain discrepancies between experimentally observed and predicted aqSOA properties.&lt;/p&gt;

scholarly journals Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid and methylglyoxal

2012 ◽  
Vol 12 (2) ◽  
pp. 801-813 ◽  
Author(s):  
Y. Tan ◽  
Y. B. Lim ◽  
K. E. Altieri ◽  
S. P. Seitzinger ◽  
B. J. Turpin
Keyword(s):  
Acetic Acid ◽  
Gas Phase ◽  
Organic Aerosol ◽  
Oh Radicals ◽  
Oh Radical ◽  
Radical Oxidation ◽  
Oligomer Formation ◽  
Acid Catalyzed ◽  
Aqueous Oxidation ◽  
Oxalic Acids

Abstract. Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 μM–10 mM) was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR

2021 ◽  
Author(s):  
Yat Sing Pang ◽  
Martin Kaminski ◽  
Anna Novelli ◽  
Philip Carlsson ◽  
Ismail-Hakki Acir ◽  
...  
Keyword(s):  
Organic Aerosol ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Reaction Pathways ◽  
Oh Radicals ◽  
Oh Radical ◽  
Simulation Experiments ◽  
Master Chemical Mechanism ◽  
Simulation Results ◽  
Atmosphere Simulation Chamber

&lt;p&gt;Limonene is the fourth-most abundant monoterpene in the atmosphere, which upon oxidation leads to the formation of secondary organic aerosol (SOA) and thereby influences climate and air quality.&lt;/p&gt;&lt;p&gt;In this study, the oxidation of limonene by OH at different atmospherically relevant NO and HO&lt;sub&gt;2&lt;/sub&gt; levels (NO: 0.1 &amp;#8211; 10 ppb; HO&lt;sub&gt;2&lt;/sub&gt;: 20 ppt) was investigated in simulation experiments in the SAPHIR chamber at Forschungszentrum J&amp;#252;lich. The analysis focuses on comparing measured radical concentrations (RO&lt;sub&gt;2&lt;/sub&gt;, HO&lt;sub&gt;2&lt;/sub&gt;, OH) and OH reactivity (k&lt;sub&gt;OH&lt;/sub&gt;) with modeled values calculated using the Master Chemical Mechanism (MCM) version 3.3.1.&lt;/p&gt;&lt;p&gt;At high and medium NO concentrations, RO&lt;sub&gt;2&lt;/sub&gt; is expected to quickly react with NO. An HO&lt;sub&gt;2&lt;/sub&gt; radical is produced during the process that can be converted back to an OH radical by another reaction with NO. Consistently, for experiments conducted at medium NO levels (~0.5 ppb, RO&lt;sub&gt;2&lt;/sub&gt; lifetime ~10 s), simulated RO&lt;sub&gt;2&lt;/sub&gt;, HO&lt;sub&gt;2&lt;/sub&gt;, and OH agree with observations within the measurement uncertainties, if the OH reactivity of oxidation products is correctly described.&lt;/p&gt;&lt;p&gt;At lower NO concentrations, the regeneration of HO&lt;sub&gt;2&lt;/sub&gt; in the RO&lt;sub&gt;2&lt;/sub&gt; + NO reaction is slow and the reaction of RO&lt;sub&gt;2&lt;/sub&gt; with HO&lt;sub&gt;2&lt;/sub&gt; gains importance in forming peroxides. However, simulation results show a large discrepancy between calculated radical concentrations and measurements at low NO levels (&lt;0.1 ppb, RO&lt;sub&gt;2&lt;/sub&gt; lifetime ~ 100 s). Simulated RO&lt;sub&gt;2&lt;/sub&gt; concentrations are found to be overestimated by a factor of three; simulated HO&lt;sub&gt;2&lt;/sub&gt; concentrations are underestimated by 50 %; simulated OH concentrations are underestimated by about 35%, even if k&lt;sub&gt;OH&lt;/sub&gt; is correctly described. This suggests that there could be additional RO&lt;sub&gt;2&lt;/sub&gt; reaction pathways that regenerate HO&lt;sub&gt;2&lt;/sub&gt; and OH radicals become important, but they are not taken into account in the MCM model.&lt;/p&gt;

scholarly journals A facile and effective method for preparation of 2.5-furandicarboxylic acid via hydrogen peroxide direct oxidation of 5-hydroxymethylfurfural

2017 ◽  
Vol 19 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Shuang Zhang ◽  
Long Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Time ◽  
Oxidation Mechanism ◽  
Molar Ratio ◽  
Alkaline Condition ◽  
Optimal Parameters ◽  
Direct Oxidation ◽  
Reaction Parameters ◽  
Alkaline Conditions ◽  
Furandicarboxylic Acid

Abstract In this paper, 2,5-furandicarboxylic acid (FDCA) was efficiently prepared by the direct oxidation of 5-hydroxymethylfurfural (5-HMF) using hydrogen peroxide (H2O2) in alkaline conditions without any catalysts. The effects of reaction parameters on the process were systematically investigated and the optimal parameters were obtained as follows: molar ratio of 5-HMF:KOH:H2O2 was 1:4:8, reaction temperature and reaction time were determined as 70°C and 15 minutes, respectively. Under these conditions, the yield of FDCA was 55.6% and the purity of FDCA could reach 99%. Moreover, we have speculated the detailed oxidation mechanism of 5-HMF assisted by hydrogen peroxide in alkaline condition to synthesize FDCA.

scholarly journals Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions

2021 ◽  
Vol 21 (17) ◽  
pp. 13333-13351
Author(s):  
Alexandre Kukui ◽  
Michel Chartier ◽  
Jinhe Wang ◽  
Hui Chen ◽  
Sébastien Dusanter ◽  
...  
Keyword(s):  
Steady State ◽  
Sulfuric Acid ◽  
Organic Compounds ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Additional Source ◽  
So2 Oxidation ◽  
Criegee Intermediates ◽  
Volatile Organic

Abstract. Reaction of stabilized Criegee intermediates (SCIs) with SO2 was proposed as an additional pathway of gaseous sulfuric acid (H2SO4) formation in the atmosphere, supplementary to the conventional mechanism of H2SO4 production by oxidation of SO2 in reaction with OH radicals. However, because of a large uncertainty in mechanism and rate coefficients for the atmospheric formation and loss reactions of different SCIs, the importance of this additional source is not well established. In this work, we present an estimation of the role of SCIs in H2SO4 formation at a western Mediterranean (Cape Corsica) remote site, where comprehensive field observations including gas-phase H2SO4, OH radicals, SO2, volatile organic compounds (VOCs) and aerosol size distribution measurements were performed in July–August 2013 as a part of the project ChArMEx (Chemistry-Aerosols Mediterranean Experiment). The measurement site was under strong influence of local emissions of biogenic volatile organic compounds, including monoterpenes and isoprene generating SCIs in reactions with ozone, and, hence, presenting an additional source of H2SO4 via SO2 oxidation by the SCIs. Assuming the validity of a steady state between H2SO4 production and its loss by condensation on existing aerosol particles with a unity accommodation coefficient, about 90 % of the H2SO4 formation during the day could be explained by the reaction of SO2 with OH. During the night the oxidation of SO2 by OH radicals was found to contribute only about 10 % to the H2SO4 formation. The accuracy of the derived values for the contribution of OH + SO2 reaction to the H2SO4 formation is limited mostly by a large, at present factor of 2, uncertainty in the OH + SO2 reaction rate coefficient. The contribution of the SO2 oxidation by SCIs to the H2SO4 formation was evaluated using available measurements of unsaturated VOCs and steady-state SCI concentrations estimated by adopting rate coefficients for SCI reactions based on structure–activity relationships (SARs). The estimated concentration of the sum of SCIs was in the range of (1–3) × 103 molec. cm−3. During the day the reaction of SCIs with SO2 was found to account for about 10 % and during the night for about 40 % of the H2SO4 production, closing the H2SO4 budget during the day but leaving unexplained about 50 % of the H2SO4 formation during the night. Despite large uncertainties in used kinetic parameters, these results indicate that the SO2 oxidation by SCIs may represent an important H2SO4 source in VOC-rich environments, especially during nighttime.

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