scholarly journals Photo degradation kinetics of insensitive munitions constituents nitroguanidine, nitrotriazolone, and dinitroanisole in natural waters

2021 ◽  
Author(s):  
Lee Moores ◽  
Stacy Jones ◽  
Garrett George ◽  
David Henderson ◽  
Timothy Schutt
Keyword(s):  
Laboratory Experiments ◽  
Natural Waters ◽  
Matrix Effects ◽  
Degradation Kinetics ◽  
Relative Rate ◽  
Ph Dependence ◽  
Degradation Pathway ◽  
Quantum Yields ◽  
The Individual ◽  
Kinetics Of

Herein the matrix effects on the kinetics of aqueous photolysis for the individual munitions constituents of IMX-101: nitroguanidine (NQ), dinitroanisole (DNAN), and nitrotriazolone (NTO) are reported along with the environmentally relevant kinetics and quantum yields. Photolysis potentially represents a major degradation pathway for these munitions in the environment and further understanding the complex matrices effects on photolytic kinetics was needed. Aqueous systems are of particular interest due to the high solubility of NQ (3,800 ppm) and NTO (16,642 ppm) compared to the traditional munitions trinitrotoluene (TNT, 100.5 ppm) and 1,3,5-trinitro-1,3,5-triazine (RDX, 59.9 ppm). Environmental half-lives (and quantum yields) were found to be 0.44 days, 0.83 days, and 4.4 days for NQ, DNAN, and NTO, respectively, under natural sunlight. In laboratory experiments using nominally 300 nm bulbs in a merry-go-round style reactor in DI water the relative rate of photolysis for the three munitions constituents followed the same order NQ > DNAN > NTO, where DNAN and NTO reacted 57 and 115 times more slowly, respectively, than NQ. In the various environmentally relevant matrices tested in the laboratory experiments NQ was not significantly affected, DNAN showed a faster degradation with increasing ionic strength, and NTO showed a modest salinity and pH dependence on its rate of photolysis.

scholarly journals Kinetics of dimethyl sulfide (DMS) reactions with isoprene-derived Criegee intermediates studied with direct UV absorption

2020 ◽  
Author(s):  
Mei-Tsan Kuo ◽  
Isabelle Weber ◽  
Christa Fittschen ◽  
Jim Jr-Min Lin
Keyword(s):  
Atmospheric Chemistry ◽  
Dimethyl Sulfide ◽  
Relative Rate ◽  
Chem Phys ◽  
High Reactivity ◽  
Rate Coefficients ◽  
Visible Absorption ◽  
Criegee Intermediates ◽  
The Individual ◽  
Kinetics Of

Abstract. Criegee intermediates (CIs) are formed in the ozonolysis of unsaturated hydrocarbons and play a role in atmospheric chemistry as a non-photolytic OH source or a strong oxidant. Using a relative rate method in an ozonolysis experiment, Newland et al. [Atmos. Chem. Phys., 15, 9521–9536, 2015] reported high reactivity of isoprene-derived Criegee intermediates towards dimethyl sulfide (DMS) relative to that towards SO2 with the ratio of the rate coefficients kDMS+CI / kSO2+CI = 3.5 ± 1.8. Here we reinvestigated the kinetics of DMS reactions with two major Criegee intermediates formed in isoprene ozonolysis, CH2OO and methyl vinyl ketone oxide (MVKO). The individual CI was prepared following reported photolytic method with suitable (diiodo) precursors in the presence of O2. The concentration of CH2OO or MVKO was monitored directly in real time through their intense UV-visible absorption. Our results indicate the reactions of DMS with CH2OO and MVKO are both very slow; the upper limits of the rate coefficients are 4 orders of magnitude smaller than that reported by Newland et al. These results suggest that the ozonolysis experiment could be complicated such that interpretation should be careful and these CIs would not oxidize atmospheric DMS at any substantial level.

Anaerobic degradation kinetics of a cholesteryl ester

2003 ◽  
Vol 48 (6) ◽  
pp. 141-147
Author(s):  
S. Gutiérrez ◽  
M. Viñas
Keyword(s):  
Palmitic Acid ◽  
Anaerobic Degradation ◽  
Drop Size ◽  
Degradation Kinetics ◽  
Relative Rate ◽  
Hydrolysis Rate ◽  
Order Kinetic ◽  
Order Kinetic Model ◽  
The Difference ◽  
Kinetics Of

The most important components of wool scouring effluent grease are esters of sterols. Cholesteryl palmitate (CP) is the main ester in this grease. In this paper, the influence of the ester concentration in the anaerobic digestion and the relative rate of the different degradation steps, are studied. The experiment was carried out to measure methane production in the anaerobic degradation of acetate, palmitic acid (PA) and CP. A first-order kinetic model was assumed for hydrolysis and Monod models were assumed for both the methanogenic and acetogenic steps. Maximum hydrolysis rate was found to be around 20 times faster than the maximum methanogenic reaction rate during the experience. The lanolin emulsion drop size effect was also evaluated employing fine and coarse stock lanolin emulsions and no adapted sludge. Concentrations of 13.7 to 4.6 gCOD.l-1 were employed. In a previous study, the effect of palmitic acid emulsion size was found important when similar sludge was tested. When esters are degraded, a significant effect of drop size on the degradation rate was not found. The difference between CP and PA emulsions behavior could be due to the fact that cholesterol produced during the ester degradation has a protective effect on the sludge.

Photooxidation of methyl ethyl ketone vapor

1967 ◽  
Vol 45 (22) ◽  
pp. 2741-2748 ◽  
Author(s):  
D. E. Hoare ◽  
D. A. Whytock
Keyword(s):  
Methyl Ethyl Ketone ◽  
Relative Rate ◽  
Quantum Yields ◽  
Methyl Ethyl ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Ethyl Group ◽  
Relative Rate Constants ◽  
The Individual ◽  
Time Extrapolation

The photochemical reaction between methyl ethyl ketone and oxygen has been studied at 150 °C with light of 3 130 Å. Measurement of the quantum yields of the major products of the reaction indicates the chain nature of the reaction, the length of the chain decreasing with increase in time. Extrapolation of quantum yields of products to zero time allows the evaluation of several relative rate constants and at least an indication of the individual radical sources of the observed products. It is shown that abstraction of hydrogen atoms from the methyl group takes place at least at a quarter the rate of abstraction of a secondary hydrogen from the ethyl group at 150 °C. In the initial products the ethyl group gives mainly acetaldehyde or perpropionic acid, the methyl group gives formaldehyde and methanol, and the carbonyl group gives carbon dioxide and perpropionic acid with a little carbon monoxide.

Photosensitized degradation kinetics of trace halogenated contaminants in natural waters using membrane introduction mass spectrometry as an in situ reaction monitor

2015 ◽  
Vol 14 (11) ◽  
pp. 2108-2118 ◽  
Author(s):  
Dane R. Letourneau ◽  
Chris G. Gill ◽  
Erik T. Krogh
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Natural Waters ◽  
Degradation Kinetics ◽  
Reductive Dehalogenation ◽  
Membrane Introduction Mass Spectrometry ◽  
Naturally Occurring ◽  
On Line ◽  
Kinetics Of

On-line membrane introduction mass spectrometry used to directly measure the photosensitized reductive dehalogenation kinetics of trace aqueous halocarbons in the presence of naturally occurring dissolved organic matter.

Degradation of Sulfamethoxazole by Electrochemically Activated Persulfate Using Iron Anode

2019 ◽  
Vol 17 (2) ◽  
Author(s):  
Lei Zheng ◽  
Hui Jin ◽  
Men Yu ◽  
Qi Zhongwei ◽  
Lingling Zhang ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Radical Scavenging ◽  
Inhibitory Effect ◽  
Degradation Pathway ◽  
Electrochemical Treatment ◽  
Interactive Effects ◽  
Paramagnetic Resonance ◽  
Iron Anode ◽  
The Individual ◽  
Activated Persulfate

Abstract In this study, sulfamethoxazole (SMX) was removed by electrochemically activated persulfate using iron anode. Different oxidation processes (persulfate alone, Fe2+/persulfate, electrolysis alone, electrochemically/Persulfate) were investigated, the results showed SMX could be more efficiently degraded under the electrochemically/Persulfate system. Central composite design (CCD) based Response surface methodology (RSM) was used to optimize and elucidate the individual and interactive effects of independent variables on the degradation kinetics of sulfamethoxazole. The maximum kinetics was predicted by CCD as pH 3.6, 18 mA applied current and 3.55 mM/L persulfate concentration. The results of free-radical scavenging experiments and electron paramagnetic resonance (EPR) indicated that both {\text{SO}}_4^{ \cdot - } and HO· were responsible for the degradation of SMX. The inhibition of methanol (MeOH) was lower than tertiary butanol (TBA), due to the generation of methanol radical (·CH2OH), which promoted the reduction of Fe3+to Fe2+. LC-ESI-TOF-MS analysis was done on SMX and its intermediates. The SMX degradation pathway during the electrochemical treatment was proposed. In addition, two typical inorganic anions ( {\text{C}}{{\text{l}}^ - },{\text{HCO}}_3^ -) were investigated and the inhibitory effect of {\text{HC}}O_3^ - was more obvious.

scholarly journals Effect of pH and concentration on the chemical stability and reaction kinetics of thiamine mononitrate and thiamine chloride hydrochloride in solution

BMC Chemistry ◽  
2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Adrienne L. Voelker ◽  
Lynne S. Taylor ◽  
Lisa J. Mauer
Keyword(s):  
Reaction Kinetics ◽  
High Performance ◽  
Degradation Kinetics ◽  
Degradation Pathway ◽  
Reaction Rate Constant ◽  
Solution Ph ◽  
Kinetics Of Degradation ◽  
One Year ◽  
Kinetics Of ◽  
Over Time

AbstractThiamine (vitamin B1) is an essential micronutrient in the human diet, found both naturally and as a fortification ingredient in many foods and supplements. However, it is susceptible to degradation due to heat, light, alkaline pH, and sulfites, among effects from other food matrix components, and its degradation has both nutritional and sensory implications as in foods. Thiamine storage stability in solution was monitored over time to determine the effect of solution pH and thiamine concentration on reaction kinetics of degradation without the use of buffers, which are known to affect thiamine stability independent of pH. The study directly compared thiamine stability in solutions prepared with different pHs (3 or 6), concentrations (1 or 20 mg/mL), and counterion in solution (NO3−, Cl−, or both), including both commercially available salt forms of thiamine (thiamine mononitrate and thiamine chloride hydrochloride). Solutions were stored at 25, 40, 60, and 80 °C for up to one year, and degradation was quantified by high-performance liquid chromatography (HPLC) over time, which was then used to calculate degradation kinetics. Thiamine was significantly more stable in pH 3 than in pH 6 solutions. In pH 6 solutions, stability was dependent on initial thiamine concentration, with the 20 mg/mL thiamine salt solutions having an increased reaction rate constant (kobs) compared to the 1 mg/mL solutions. In pH 3 solutions, kobs was not dependent on initial concentration, attributed to differences in degradation pathway dependent on pH. Activation energies of degradation (Ea) were higher in pH 3 solutions (21–27 kcal/mol) than in pH 6 solutions (18–21 kcal/mol), indicating a difference in stability and degradation pathway due to pH. The fundamental reaction kinetics of thiamine reported in this study provide a basis for understanding thiamine stability and therefore improving thiamine delivery in many foods containing both natural and fortified thiamine.

scholarly journals Kinetics of dimethyl sulfide (DMS) reactions with isoprene-derived Criegee intermediates studied with direct UV absorption

2020 ◽  
Vol 20 (21) ◽  
pp. 12983-12993
Author(s):  
Mei-Tsan Kuo ◽  
Isabelle Weber ◽  
Christa Fittschen ◽  
Luc Vereecken ◽  
Jim Jr-Min Lin
Keyword(s):  
Atmospheric Chemistry ◽  
Dimethyl Sulfide ◽  
Relative Rate ◽  
High Reactivity ◽  
Rate Coefficients ◽  
Visible Absorption ◽  
Criegee Intermediates ◽  
Upper Limits ◽  
The Individual ◽  
Kinetics Of

Abstract. Criegee intermediates (CIs) are formed in the ozonolysis of unsaturated hydrocarbons and play a role in atmospheric chemistry as a non-photolytic OH source or a strong oxidant. Using a relative rate method in an ozonolysis experiment, Newland et al. (2015) reported high reactivity of isoprene-derived Criegee intermediates towards dimethyl sulfide (DMS) relative to that towards SO2 with the ratio of the rate coefficients kDMS+CI/kSO2+CI = 3.5 ± 1.8. Here we reinvestigated the kinetics of DMS reactions with two major Criegee intermediates formed in isoprene ozonolysis, CH2OO, and methyl vinyl ketone oxide (MVKO). The individual CI was prepared following the reported photolytic method with suitable (diiodo) precursors in the presence of O2. The concentration of CH2OO or MVKO was monitored directly in real time through their intense UV–visible absorption. Our results indicate the reactions of DMS with CH2OO and MVKO are both very slow; the upper limits of the rate coefficients are 4 orders of magnitude smaller than the rate coefficient reported by Newland et al. (2015) These results suggest that the ozonolysis experiment could be complicated such that interpretation should be careful and these CIs would not oxidize atmospheric DMS at any substantial level.

Environmental Matrix Effects on Degradation Kinetics of Ibuprofen in a UV/ Persulfate System

2018 ◽  
Vol 21 (1) ◽  
pp. 138-148 ◽  
Author(s):  
Rongkui Su ◽  
Zongsu Wei ◽  
Shuang Luo ◽  
Richard Spinney ◽  
Lingwei Gao ◽  
...  
Keyword(s):  
Matrix Effects ◽  
Degradation Kinetics ◽  
Kinetics Of

scholarly journals Characterization of deltamethrin degradation and metabolic pathway by co-culture of Acinetobacter junii LH-1-1 and Klebsiella pneumoniae BPBA052

2020 ◽  
Author(s):  
Jie Tang ◽  
Qiong Hu ◽  
Dan Lei ◽  
Min Wu ◽  
Chaoyi Zeng ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Contaminated Soils ◽  
Degradation Kinetics ◽  
Degradation Pathway ◽  
Gas Chromatography Mass Spectrometry ◽  
Acinetobacter Junii ◽  
Pyrethroid Pesticides ◽  
First Time ◽  
Kinetics Of

Abstract Deltamethrin and its major metabolite 3-phenoxybenzoic acid (3‐PBA) have caused serious threat to the environment as well as human health, yet little is known about their degradation pathways by bacterial co-cultures. In this study, the growth and degradation kinetics of Acinetobacter junii LH-1-1 and Klebsiella pneumoniae BPBA052 during deltamethrin and 3-PBA degradation were established, respectively. When the inoculum proportion of the strains LH-1-1 and BPBA052 was 7.5:2.5, and LH-1-1 was inoculated 24 h before inoculation of strain BPBA052, 94.25% deltamethrin was degraded and 9.16 mg/L of 3-PBA remained within 72 h, which was 20.36% higher and 10.25 mg/L lesser than that in monoculture of LH-1-1, respectively. And the half-life of deltamethrin was shortened from 38.40 h to 24.58 h. Based on gas chromatography–mass spectrometry, 3-phenoxybenzaldehyde, 1,2-benzenedicarboxylic butyl dacyl ester, and phenol were identified as metabolites during deltamethrin degradation in co-culture. This is the first time that a co-culture degradation pathway of deltamethrin has been proposed based on these identified metabolites. Bioremediation of deltamethrin-contaminated soils with co-culture of strains LH-1-1 and BPBA052 significantly enhanced deltamethrin degradation and 3-PBA removal. This study provides a platform for further studies on deltamethrin and 3-PBA biodegradation mechanism in co-culture, and it also proposes a promising approach for efficient bioremediation of environment contaminated by pyrethroid pesticides and their associated metabolites.

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