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>

scholarly journals Detoxification of As(III) in Aqueous Media by Using Photo-Fenton Method

2021 ◽  
Keyword(s):  
Aqueous Solution ◽  
Reaction Time ◽  
Contact Time ◽  
Uv Light ◽  
Aqueous Media ◽  
Oh Radicals ◽  
Fenton Process ◽  
Photo Oxidation ◽  
Experimental Parameters ◽  
Three Stages

<p>In this paper, photo-Fenton method has been systematically examined to oxidize the toxic and mobile As(III) in the solution by •OH radicals resulted from the reactions between Fe2+ and H2O2 under UV light, to form the less toxic and insoluble As(V). The effects of various experimental parameters including initial Fe2+ and H2O2 concentrations, working pH, and contact time were studied through a batch experiment. The concentration of As(V) resulted from the photo-oxidation was determined by visible spectrophotometry method based on the formation of arsenate molybdate solution. The results of the research attributed noticeably that the As(III) could be oxidized through photo-Fenton process to form As(V) that was assigned by a considerable decline in the concentration. The maximal oxidation of As(III) with 10 mg L-1 of the concentration in 50 mL of the aqueous solution, that was about 85%, can be reached in the presence of Fe2+ 10-2 mole L-1, H2O2 5. 10-2 mole L-1 at the working pH 3 and within 3 h of the reaction time. It has been also detected that for reaching the permissible level (lower than 0.01 mg L-1 ), three stages of the photo-Fenton process were required.</p>

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.

Effect of Reaction Time on the Morphology and Photocatalytic Property of ZnO Nanoparticles

2017 ◽  
Vol 726 ◽  
pp. 365-369
Author(s):  
Xia Kong ◽  
Ya Wei Hu ◽  
Wei Pan
Keyword(s):  
Aqueous Solution ◽  
Methylene Blue ◽  
Reaction Time ◽  
Uv Irradiation ◽  
Zno Nanoparticles ◽  
Uv Light ◽  
Photocatalytic Property ◽  
Crystallographic Structure ◽  
Elliptical Shape ◽  
One Step

Abstract. ZnO nanoparticles with different morphology were synthesized through a one-step and low temperature hydrothermal method with different reaction time. The prepared ZnO nanoparticles have been used as photocatalysts for the degradation of methylene blue (MB) aqueous solution under UV irradiation to study the relationship between the morphology and photocatalytic performance. The phase, crystallographic structure and morphology of synthesised ZnO nanoparticles were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The photocatalytic activity of ZnO nanoparticles were carried out by UV-visible spectroscopy (UV-vis). SEM results showed that different particle sizes and morphologies of flower-like, elliptical-shape and rod-shapes were obtained at 60 °C for 1 h, 4 h, 8 h and 12 h, which promoted photodegradation of methylene blue (MB) aqueous solution under UV light irradiation. Especially, elliptical-shape ZnOnanoparticles with reaction time of 4 h were most efficient, and the degradation rate was up to 98.2% after 20 min UV irradiation.

scholarly journals Photo-degradation ibuprofen by UV/H2O2 process: response surface analysis and degradation mechanism

2017 ◽  
Vol 75 (12) ◽  
pp. 2935-2951 ◽  
Author(s):  
Mingguo Peng ◽  
Huajie Li ◽  
Xu Kang ◽  
Erdeng Du ◽  
Dongdong Li
Keyword(s):  
Aqueous Solution ◽  
Response Surface ◽  
Ph Value ◽  
Uv Light ◽  
Degradation Products ◽  
Degradation Mechanism ◽  
Oh Radical ◽  
Initial Ph ◽  
Rsm Model ◽  
Degradation Intermediates

The removal of ibuprofen (IBP) in aqueous solution using UV/H2O2 process was evaluated. The response surface methodology (RSM) and Box–Behnken design were employed to investigate the effects of process parameters on IBP removal, including the initial IBP concentration, H2O2 dosage, UV light intensity, and initial pH value of solution. The RSM model developed herein fits well with the experiments, and provides a good insight into the OH radical irritated degradation mechanisms and kinetics. High resolution accurate mass spectrometry coupled with liquid chromatography was used to identify the degradation intermediates. A total of 23 degradation products were identified, including mono-hydroxylated products and dihydroxylated products. A series of OH radical-initiated reactions, including hydroxylation, dihydroxylation, decarboxylation, demethylation, ring break, lead to the final mineralization of IBP to CO2 and H2O. UV/H2O2 technology could be a promising technology for IBP removal in aqueous solution.

Pulsradiolytische Untersuchung zur Oxidation der Ascorbinsäure durch OH-Radikale und Halogen-Radikal-Komplexe in wäßriger Lösung / Pulse Radiolysis Studies of the Oxidation of Ascorbic Acid by OH-radicals and Halide Radical Anion Complexes in Aqueous Solution

1972 ◽  
Vol 27 (6) ◽  
pp. 649-659 ◽  
Author(s):  
M. Schöneshöfer
Keyword(s):  
Aqueous Solution ◽  
Ascorbic Acid ◽  
Radical Anion ◽  
Oh Radicals ◽  
Oh Radical ◽  
Extinction Coefficients ◽  
Acid Radical ◽  
Tautomeric Forms ◽  
Anion Complexes ◽  
Millisecond Range

Ascorbic acid is oxidized by the OH radical and by radical anion complexes X2⁻ (X: Cl, Br, J, SCN) to yield the “ascorbic acid radical”which finally disappears by second order. The pK of this radical was found to be about 3. It has several precursor radicals formed by the addition of OH or X to ascorbic acid. They lose H2O or HX, respectively, with different rates or are desactivated in radical-radical reactions. The precursor radicals are acids of different pK values. Since ascorbic acid exists in two tautomeric forms in aqueous solution, two precursor radicals are postulated for the reaction of OH with ascorbic acid:They lose water or OH⁻ with different rates to form the ascorbic acid radical. The absorption spectra of these species were measured. All radicals including the ascorbic acid radical have strong absorption at 3600 A, although somewhat different extinction coefficients. The decay of the 3600 A absorption in the 100 μs and millisecond range, which in earlier work of BIELSKI et al. 3 has been attributed solely to the disappearance of the ascorbic acid radical is partly due to the loss of water of long-lived precursors and to radical-radical desactivation of precursors and the ascorbic acid radical. Earlier conclusions of BIELSKI et al. about the pK of the ascorbic acid radical and about its protonization cannot be confirmed taking into consideration the complex precursor reactions. The kinetics is strongly dependent on the dose below about 400 rad. The precursor radicals formed by the addition of X to ascorbic acid are generally shorter lived than the OH addition precursors.

Effect of Heat Treatment on the Micro-Structural, Crystallinity and Photocatalytic Properties of Hydrothermally Prepared Titanate Nanowires

2016 ◽  
Vol 1133 ◽  
pp. 13-17
Author(s):  
Mohamad Siti Mariam ◽  
A.B. Siti Najihah ◽  
A.Z. Zuhana ◽  
M. Abd Kadir
Keyword(s):  
Aqueous Solution ◽  
Uv Light ◽  
Irradiation Time ◽  
Anatase Phase ◽  
Hydrothermal Process ◽  
Sodium Titanate ◽  
Xrd Analysis ◽  
Sample Heat ◽  
Heat Treated ◽  
Titanate Nanowires

Titanate nanowires were synthesised by hydrothermal process in 10M NaOH aqueous solution at 200oC for 24h. The samples were washed repeatedly in HCl aq. solution and deionized water until pH ~7. Subsequently, the samples were heat-treated at 400-850°C in air for 2h. The X-ray diffraction (XRD) analysis of the sample heat-treated at 800°C showed the crystalline structure of sodium titanate (Na2Ti6O13 ), while the presence of anatase phase was detected from the sample heat-treated at 850°C. Wire-like morphology of the synthesized sample was observed using FE-SEM. The photocatalytic activity of the samples heat-treated at 600,800, 850°C and 900°C was investigated by measuring the degradation of methylene blue (MB) in aqueous solution under UV-light irradiation and more than 90% of the dye was efficiently degraded by the sample heat-treated at 850°C within 45 minutes irradiation time as compared to other tested samples.

scholarly journals Molecular composition of aged secondary organic aerosol generated from a mixture of biogenic volatile compounds using ultrahigh resolution mass spectrometry

2015 ◽  
Vol 15 (4) ◽  
pp. 5359-5389 ◽  
Author(s):  
I. Kourtchev ◽  
J.-F. Doussin ◽  
C. Giorio ◽  
B. Mahon ◽  
E. M. Wilson ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Uv Light ◽  
Radical Reaction ◽  
Organic Aerosol ◽  
Molecular Composition ◽  
Oh Radicals ◽  
Oh Radical ◽  
Ultrahigh Resolution ◽  
Ageing Processes ◽  
Resolution Mass

Abstract. Field observations over the past decade indicate that a significant fraction of organic aerosol in remote areas may contain highly oxidised molecules. Aerosol processing or further oxidation (ageing) of organic aerosol has been suggested to be responsible for their formation through heterogeneous uptake of oxidants and multigenerational oxidation of vapours by OH radicals. In this study we investigated the influence of several ageing processes on the molecular composition of secondary organic aerosols (SOA) using direct infusion and liquid chromatography ultrahigh resolution mass spectrometry. SOA was formed in simulation chamber experiments from ozonolysis of a mixture of four biogenic volatile organic compounds (BVOC): α-pinene, β-pinene, Δ3-carene and isoprene. The SOA was subsequently aged under three different sets of conditions: in the dark in the presence of residual ozone, with UV irradiation and OH radicals, and using UV light only. Among all studied conditions, only OH radical-initiated ageing was found to influence the molecular composition of the aerosol and showed an increase in carbon oxidation state (OSC) and elemental O/C ratios of the SOA components. None of the ageing processes produced an observable effect on the oligomers formed from ozonolysis of the BVOC mixture, which were found to be equally abundant in both "fresh" and "aged" SOA. Additional experiments using α-pinene as the sole precursor demonstrated that oligomers are an important group of compounds in SOA produced from both ozonolysis and OH radical-initiated oxidation processes; however, a completely different set of oligomers is formed under these two oxidation regimes. SOA from the OH radical-initiated α-pinene oxidation had a significantly higher overall OSC and O/C compared to that from pure ozonolysis experiments confirming that the OH radical reaction is more likely to be responsible for the occurrence of highly oxidised species in ambient biogenic SOA.

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.

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.

Decolorization of Reactive Blue 220 aqueous solution using fungal synthesized Co3O4 nanoparticles

2019 ◽  
Vol 68 (8) ◽  
pp. 675-686 ◽  
Author(s):  
Riya Sidhikku Kandath Valappil ◽  
Ajuy Sundar Vijayanandan ◽  
Raj Mohan Balakrishnan
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Photocatalytic Activity ◽  
Reaction Time ◽  
Reaction Kinetics ◽  
Uv Light ◽  
Textile Dye ◽  
Co3o4 Nanoparticles ◽  
Alkaline Ph ◽  
Uv Light Irradiation

Abstract In this work, the photocatalytic activity of the biosynthesized cobalt oxide (Co3O4) nanoparticle (NP) is investigated using a textile dye Reactive Blue 220 (RB220) and decolorization % was monitored using UV–Vis spectrophotometer. The photocatalytic activity has been observed maximum at alkaline pH of 9, NP dosage of 250 mg/L, and reaction time of 270 min. In the presence of UV light irradiation, a maximum dye concentration of 10 mg/L was treated effectively using 150 mg/L NP, and 67% decolorization was achieved. Reaction kinetics has been analyzed, and the reaction followed the pseudo kinetics model with an activation energy of −484 kJ mol−1.

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