scholarly journals Degradation of Ketamine and Methamphetamine by the UV/H2O2 System: Kinetics, Mechanisms and Comparison

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2999
Author(s):  
De-Ming Gu ◽  
Chang-Sheng Guo ◽  
Qi-Yan Feng ◽  
Heng Zhang ◽  
Jian Xu
Keyword(s):  
Reaction Kinetics ◽  
Rate Constants ◽  
Water Environment ◽  
Degradation Mechanisms ◽  
Psychoactive Substances ◽  
Pseudo First Order Reaction ◽  
Potential Harm ◽  
First Order ◽  
Effective Removal ◽  
H2o2 System

The illegal use and low biodegradability of psychoactive substances has led to their introduction to the natural water environment, causing potential harm to ecosystems and human health. This paper compared the reaction kinetics and degradation mechanisms of ketamine (KET) and methamphetamine (METH) by UV/H2O2. Results indicated that the degradation of KET and METH using UV or H2O2 alone was negligible. UV/H2O2 had a strong synergizing effect, which could effectively remove 99% of KET and METH (100 μg/L) within 120 and 60 min, respectively. Their degradation was fully consistent with pseudo-first-order reaction kinetics (R2 > 0.99). Based on competition kinetics, the rate constants of the hydroxyl radical with KET and METH were calculated to be 4.43 × 109 and 7.91 × 109 M−1·s−1, respectively. The apparent rate constants of KET and METH increased respectively from 0.001 to 0.027 and 0.049 min−1 with the initial H2O2 dosage ranging from 0 to 1000 μM at pH 7. Their degradation was significantly inhibited by HCO3−, Cl−, NO3− and humic acid, with Cl− having relatively little effect on the degradation of KET. Ultraperformance liquid chromatography with tandem mass spectrometry was used to identify the reaction intermediates, based on which the possible degradation pathways were proposed. These promising results clearly demonstrated the potential of the UV/H2O2 process for the effective removal of KET and METH from contaminated wastewater.

On the Chemical Reactivity of the Phytochrome Chromophore in the Pr and Pfr Form

1985 ◽  
Vol 40 (3-4) ◽  
pp. 215-218 ◽  
Author(s):  
Fritz Thümmler ◽  
Peter Eilfeld ◽  
Wolfhart Rüdiger ◽  
Doo-Khil Moon ◽  
Pill-Soon Song
Keyword(s):  
Reaction Kinetics ◽  
Rate Constants ◽  
Chemical Reactivity ◽  
Order Reaction ◽  
First Order Reaction ◽  
Limiting Factor ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Pseudo First Order ◽  
The Difference

The reactivity of the phytochrome chromophore and related tetrapyrroles towards ozone and tetranitromethane was investigated. Both oxidizing reagents cause bleaching of the main absorp­tion band of the pigment. The rate constants for this bleaching were determined under conditions of pseudo first order reaction kinetics. The rate constants for the reaction with ozone are similar for native phytochrome and for freely accessible tetrapyrroles (biliverdin, small chromopeptides from phytochrome) indicating that accessibility is not the limiting factor for the reaction with ozone. Under a variety of conditions, the Pfr chromophore reacts by about 10% faster than the Pr chromophore. This may reflect the true difference in reactivity. The rate constants for the reaction with tetranitromethane are much larger for biliverdin, bilirubin and small chromopeptides from phytochrome than for native phytochrome. The limiting factor for this reaction in native phytochrome therefore is the accessibility of the chromophore by the reagent. Previous conclusions on the difference in exposure of the tetrapyrrole chromophore in Pr and Pfr are confirmed.

scholarly journals KINETICS OF PALM OIL TRANSESTERIFICATION IN METHANOL WITH POTASSIUM HYDROXIDE AS A CATALYST

2010 ◽  
Vol 8 (2) ◽  
pp. 219-225
Author(s):  
Yoeswono Yoeswono ◽  
Triyono Triyono ◽  
Iqmal Tahir
Keyword(s):  
Activation Energy ◽  
Palm Oil ◽  
Rate Constants ◽  
Potassium Hydroxide ◽  
Catalyst Concentration ◽  
Time Interval ◽  
Pseudo First Order Reaction ◽  
Exponential Factor ◽  
Potassium Methoxide ◽  
First Order

A study on palm oil transesterification to evaluate the effect of some parameters in the reaction on the reaction kinetics has been carried out. Transesterification was started by preparing potassium methoxide from potassium hydroxide and methanol and then mixed it with the palm oil. An aliquot was taken at certain time interval during transesterification and poured into test tube filled with distilled water to stop the reaction immediately. The oil phase that separated from the glycerol phase by centrifugation was analyzed by 1H-NMR spectrometer to determine the percentage of methyl ester conversion. Temperature and catalyst concentration were varied in order to determine the reaction rate constants, activation energies, pre-exponential factors, and effective collisions. The results showed that palm oil transesterification in methanol with 0.5 and 1 % w/w KOH/palm oil catalyst concentration appeared to follow pseudo-first order reaction. The rate constants increase with temperature. After 13 min of reaction, More methyl esters were formed using KOH 1 % than using 0.5 % w/w KOH/palm oil catalyst concentration. The activation energy (Ea) and pre-exponential factor (A) for reaction using 1 % w/w KOH was lower than those using 0.5 % w/w KOH.   Keywords: palm oil, transesterification, catalyst, first order kinetics, activation energy, pre-exponential factor

Pseudo-first order reaction kinetics and thermodynamic properties study of neem oil esterification using MgO grafted natural hydroxyapatite

RSC Advances ◽  
2016 ◽  
Vol 6 (11) ◽  
pp. 8892-8901 ◽  
Author(s):  
Himadri Sahu ◽  
Kaustubha Mohanty
Keyword(s):  
Thermodynamic Properties ◽  
Reaction Kinetics ◽  
Fish Bone ◽  
Order Reaction ◽  
Neem Oil ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Pseudo First Order ◽  
Natural Hydroxyapatite ◽  
Kinetics And Thermodynamic

In this work, waste fish bone was used as a source of natural hydroxyapatite which was later used for the preparation of a metal grafted catalyst.

Photocatalytic degradation of parathion in aqueous TiO2 dispersion: the effect of hydrogen peroxide and light intensity

1998 ◽  
Vol 37 (8) ◽  
pp. 187-194 ◽  
Author(s):  
Tsu-feng Chen ◽  
Ruey-an Doong ◽  
Wen-gang Lei
Keyword(s):  
Hydrogen Peroxide ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Photocatalytic Oxidation ◽  
Pseudo First Order Reaction ◽  
Direct Photolysis ◽  
First Order ◽  
The Relationship ◽  
Effect Of Light ◽  
H2o2 System

The photodegradation of parathion in the direct photolysis, UV/TiO2, UV/H2O2 and UV/TiO2/H2O2 systems was investigated at 25°C. The effect of light intensity was also examined to clarify the relationship between the photo flux and decomposition rate of parathion. Results of the study demonstrated that no obvious degradation of parathion in dark reaction occurred within 24 hours. However, the addition of TiO2 and/or H2O2 promotes the degradation efficiency of parathion. Adding H2O2 was more effective in the photocatalytic oxidation of parathion than TiO2. Also, hydrogen peroxide was found as an intermediate with the maximum concentration of 55 μM in UV/TiO2 system during the photodegradation of parathion. A higher intensity of lamp could increase the degradation rate of parathion. However, the quantum efficiency for degradation of parathion decreased from 0.053 to 0.006 when light intensity increased from 100 W to 450W. Photodecomposition followed a pseudo-first-order reaction. The rate constants of parathion ranged from 0.003 min−1 for direct photolysis to 0.023 min−1 for UV/TiO2/H2O2 system. This study indicated that photocatalytic degradation is a highly promising technology for detoxifying parathion.

scholarly journals Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique

2012 ◽  
Vol 19 (1) ◽  
pp. 55-66 ◽  
Author(s):  
Marta Siemieniec ◽  
Hanna Kierzkowska-Pawlak ◽  
Andrzej Chacuk
Keyword(s):  
Carbon Dioxide ◽  
Reaction Kinetics ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Stopped Flow ◽  
First Order ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Good Agreement

Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique The pseudo-first-order rate constants (kOV) for the reactions between CO2 and diethanolamine have been studied using the stopped-flow technique in an aqueous solution at 293, 298, 303 and 313 K. The amine concentrations ranged from 167 to 500 mol·m-3. The overall reaction rate constant was found to increase with amine concentration and temperature. Both the zwitterion and termolecular mechanisms were applied to correlate the experimentally obtained rate constants. The values of SSE quality index showed a good agreement between the experimental data and the corresponding fit by the use of both mechanisms.

scholarly journals Photocatalytic degradation of natural organic matter: Kinetic considerations and light intensity dependence

2004 ◽  
Vol 6 (2) ◽  
pp. 73-80 ◽  
Author(s):  
Ceyda Senem Uyguner ◽  
Miray Bekbolet
Keyword(s):  
Humic Acid ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Rate Constants ◽  
Reaction Rates ◽  
Order Reaction ◽  
First Order Reaction ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Pseudo First Order

The current study was conducted to investigate the photocatalytic degradation kinetics of humic acid at different light intensities using commercialTiO2powders. The pseudo first order kinetic model and Langmuir-Hinshelwood (L-H) rate equation in modified forms were used to compare the photocatalytic activities ofTiO2materials as a function of light intensity. Under constant irradiation conditions, the pseudo first order reaction rates as well as L-H rates were found to be decreasing in the following trend; Degussa P-25, Millennium PC-500 and Millennium PC-100. The pseudo first order rate constants showed the same decreasing trend as the pseudo first order reaction rates while L-H rate constants exhibited a light intensity related change in the ordering of the photocatalysts. At the lowest light intensity, L-H rate constants decreased as follows: Millennium PC-500>Millennium PC-100>Degussa P-25. However, increasing the light intensity changed the order to; Millennium PC-100>Millennium PC-500>Degussa P-25 revealing the significance of the L-H adsorption constant. Under constant irradiation conditions, ionic strength dependent changes in the structure of humic acid did not alter degradation efficiency trend of the photocatalyst specimens and they were ordered such as; Degussa P-25>Millennium PC-500>Hombikat UV-100>Millennium PC-100 > Merck. The results presented in this research also confirmed the effectiveness of Degussa P-25 as a photocatalyst for the degradation of humic acid.

scholarly journals Simple Urea Immersion Enhanced Removal of Tetracycline from Water by Polystyrene Microspheres

2018 ◽  
Vol 15 (7) ◽  
pp. 1524
Author(s):  
Junjun Ma ◽  
Bing Li ◽  
Lincheng Zhou ◽  
Yin Zhu ◽  
Ji Li ◽  
...  
Keyword(s):  
Surface Modification ◽  
Adsorption Mechanism ◽  
Water Environment ◽  
Order Rate Constant ◽  
Maximum Adsorption Capacity ◽  
Polystyrene Microspheres ◽  
Multilayer Adsorption ◽  
First Order ◽  
Adsorption Capacities ◽  
Effective Removal

Antibiotics pose potential ecological risks in the water environment, necessitating their effective removal by reliable technologies. Adsorption is a conventional process to remove such chemicals from water without byproducts. However, finding cheap adsorbents with satisfactory performance is still a challenge. In this study, polystyrene microspheres (PSM) were enhanced to adsorb tetracycline by surface modification. Simple urea immersion was used to prepare urea-immersed PSM (UPSM), of which surface groups were characterized by instruments to confirm the effect of immersion. Tetracycline hydrochloride (TC) and doxycycline (DC) were used as typical adsorbates. The adsorptive isotherms were interpreted by Langmuir, Freundlich, and Tempkin models. After urea immersion, the maximum adsorption capacity of UPSM at 293 K and pH 6.8 increased about 30% and 60%, achieving 460 mg/g for TC and 430 mg/g for DC. The kinetic data were fitted by first-order and second-order kinetics and Weber–Morris models. The first-order rate constant for TC adsorption on UPSM was 0.41 /h, and for DC was 0.33 /h. The cyclic urea immersion enabled multilayer adsorption, which increased the adsorption capacities of TC on UPSM by two to three times. The adsorption mechanism was possibly determined by the molecular interaction including π–π forces, cation-π bonding, and hydrogen bonding. The simple surface modification was helpful in enhancing the removal of antibiotics from wastewater with similar structures.

The influence of solution matrix on the photocatalytic removal of color from natural waters

1998 ◽  
Vol 38 (6) ◽  
pp. 155-162 ◽  
Author(s):  
M. Bekbölet ◽  
Z. Boyacioglu ◽  
B. özkaraova
Keyword(s):  
Reaction Kinetics ◽  
Natural Waters ◽  
Removal Rate ◽  
Color Removal ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Phosphate Ions ◽  
Photocatalytic Removal ◽  
Adsorption Data ◽  
Pseudo First Order

Photocatalytic color removal of humic acid was studied in the presence of common inorganic anions; namely, chloride, nitrate, sulfate and phosphate ions at pH 6.8. Color removal rates were explained in terms of pseudo-first order and Langmuir-Hinshelwood kinetics. The Freundlich adsorption data were also evaluated to assess a relationship between the adsorption data and the reaction kinetics. The presence of chloride, nitrate and sulfate ions exhibited different trends when the rate is expressed as pseudo-first order reaction kinetics. In case of Langmuir-Hinshelwood kinetics, the decolorization rates were decreased in the order of the anions as, chloride, nitrate and sulfate. The presence of phosphate ions strongly inhibited the color removal rate.

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