The photoconversion of gamma-hexachlorocyclohexane under UV irradiation in water, snow and ice

2013 ◽  
Vol 68 (11) ◽  
pp. 2479-2484 ◽  
Author(s):  
Honghai Xue ◽  
Xiaojian Tang ◽  
Chunli Kang ◽  
Jia Liu ◽  
Lei Shi ◽  
...  
Keyword(s):  
Chlorine Atom ◽  
Organic Pollutants ◽  
Uv Irradiation ◽  
Inorganic Ions ◽  
Kinetics Model ◽  
Inhibition Effect ◽  
First Order ◽  
First Order Kinetics ◽  
The Common ◽  
Snow And Ice

The photochemistry of organic pollutants has received increasing attention in ice and snow. In this work, the photoconversion of gamma-hexachlorocyclohexane (γ-HCH) under UV irradiation was investigated in water, snow and ice. The photoconversion rate, products and mechanisms were inspected, and the effect of inorganic ions (NO2−, NO3−, HCO3− and Fe2+) was discussed. The results showed that γ-HCH could be photoconverted in water, snow and ice, with the photoconversion rate being fastest in snow, and slowest in ice. All photoconversion could be described by the first-order kinetics model. In water, snow and ice, the common photoproducts of γ-HCH were alpha-hexachlorocyclohexane (α-HCH) and pentachlorocyclohexene. α-HCH was generated by a change in the bonding of a chlorine atom in γ-HCH; pentachlorocyclohexene was generated by the removal of a molecule of chlorine hydride from a molecule of γ-HCH. Different concentrations of NO2−, NO3− and HCO3− all inhibited the photoconversion of γ-HCH, and the inhibition effect decreased with increasing concentrations of NO2− and NO3−, but increased with the increasing concentrations of HCO3−. Different concentrations of Fe2+ promoted the photoconversion of γ-HCH in water and ice, but had little effect in snow.

Decolourization of Methylene Blue by Persulfate

2013 ◽  
Vol 634-638 ◽  
pp. 76-80
Author(s):  
Wei Hu ◽  
Shen Xin Li ◽  
Cheng Duan Wang
Keyword(s):  
Methylene Blue ◽  
Ionic Strength ◽  
Uv Irradiation ◽  
Reaction Temperature ◽  
Uv Light ◽  
Kinetics Model ◽  
Dye Wastewater ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order

The decolourization of dye wastewater by persulfate was studied using methylene blue as a model dye wastewater. Effects of several parameters, such as dose of oxidant, ionic strength, pH, temperature and UV irradiation, were investigated in detail. The results showed that the decolourization reaction of methylene blue by persulfate could be fitted to a pseudo-first order kinetics model. In addition, when the oxidant amount used is 2 times of methylene blue, pH 3.43 and reaction temperature for 60°C, after uv light under the irradiation of 20 min, methylene blue decolorization rate can reach more than 98%. The results are useful for the treatment of dye wastewater.

Decolourization of Kiscolon Scarlet 2KN by Persulfate

2013 ◽  
Vol 864-867 ◽  
pp. 256-260
Author(s):  
Wei Hu ◽  
Shen Xin Li ◽  
Wang Ying ◽  
Cheng Duan Wang
Keyword(s):  
Uv Irradiation ◽  
Reaction Temperature ◽  
Kinetics Model ◽  
Dye Wastewater ◽  
First Order ◽  
Decolorization Rate ◽  
First Order Kinetics ◽  
Pseudo First Order

The decolourization of dye wastewater by persulfate was studied using kiscolon scarlet2KN as a model dye wastewater. Effects of several parameters, such as dose of oxidant, pH, temperature and UV irradiation, were investigated in detail. The results showed that the decolourization reaction of kiscolon scarlet2KN by persulfate could be fitted to a pseudo-first order kinetics model. In addition, when the oxidant amount used is 70 times of kiscolon scarlet2KN, pH 5.71 and reaction temperature for 70°C, kiscolon scarlet2KN decolorization rate can reach more than 98%. The results are useful for the treatment of dye wastewater.Keywords:Kiscolon scarlet 2KN, Decolourization, Persulfate

Decolourization of Alizarin Red by Persulfate

2012 ◽  
Vol 610-613 ◽  
pp. 300-305
Author(s):  
Shen Xin Li ◽  
Wei Hu ◽  
Cheng Duan Wang
Keyword(s):  
Ionic Strength ◽  
Uv Irradiation ◽  
Degradation Products ◽  
Kinetics Model ◽  
Dye Wastewater ◽  
Alizarin Red ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order

The decolourization of dye wastewater by persulfate was studied using alizarin red as a model dye wastewater. Effects of several parameters, such as dose of oxidant, ionic strength, pH, temperature and UV irradiation, were investigated in detail. The results showed that the decolourization reaction of alizarin red by persulfate could be fitted to a pseudo-first order kinetics model. In addition, no degradation products were observed during the decolourization of alizarin red by persulfate. The results are useful for the treatment of dye wastewater.

scholarly journals Bleaching of chlorophylls by UV irradiation in vitro: The effects on chlorophyll organization in acetone and n-hexane

2008 ◽  
Vol 73 (3) ◽  
pp. 271-282 ◽  
Author(s):  
Jelena Zvezdanovic ◽  
Dejan Markovic
Keyword(s):  
Uv Irradiation ◽  
Photosynthetic Pigments ◽  
Energy Input ◽  
First Order ◽  
First Order Kinetics ◽  
Uv Photons ◽  
The Stability ◽  
Major Factors

The stability of chlorophylls toward UV irradiation was studied by Vis spectrophotometry in extracts containing mixtures of photosynthetic pigments in acetone and n-hexane. The chlorophylls underwent destruction (bleaching) obeying first-order kinetics. The bleaching was governed by three major factors: the energy input of the UV photons, the concentration of the chlorophylls and the polarity of the solvent, implying different molecular organizations of the chlorophylls in the two solvents.

scholarly journals Effects of continuous UV-irradiation on the antioxidant activities of quercetin and rutin in solution in the presence of lecithin as the protective target

2011 ◽  
Vol 76 (7) ◽  
pp. 973-985 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic ◽  
Dragana Cvetkovic ◽  
Blaga Radovanovic
Keyword(s):  
Lipid Peroxidation ◽  
Uv Irradiation ◽  
Energy Input ◽  
Antioxidant Activities ◽  
Antioxidant Action ◽  
First Order ◽  
First Order Kinetics ◽  
Uv Photons ◽  
Uv C

The stabilities and antioxidant action of two selected flavonoids, quercetin and rutin, dissolved in methanol and water, toward continuous UV-irradiation from three different sub-ranges (UV-A, UV-B and UV-C) were studied. The flavonoids underwent degradation (bleaching) following first-order kinetics. The bleaching rates were highly dependent on the energy input of the involved UV-photons. The antioxidant activities of the two flavonoids on UV-induced lecithin lipid peroxidation were studied by the TBA-MDA test, and appeared to be also affected by the continuous UV irradiation. The energy input of the incident UV-photons again played a major governing role, but an impact of the flavonoids structures cannot be neglected.

scholarly journals Stability of carotenoids toward UV-irradiation in hexane solution

2008 ◽  
Vol 73 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic
Keyword(s):  
Free Radical ◽  
Uv Irradiation ◽  
First Order ◽  
Chemical Structures ◽  
First Order Kinetics ◽  
Uv C ◽  
Hexane Solution

The stabilities of four selected carotenoids dissolved in hexane, two carotenes and two xanthophylls, toward UV-irradiation of three different ranges (UV-A, UV-B and UV-C) were studied in this work. The carotenoids underwent bleaching via a probable free radical mediated mechanism following first-order kinetics. The bleaching rates were highly dependent on the input of the involved photons and, although not consistently, on the chemical structures of the investigated compounds. For the two xanthophylls, a possible role of oxygen associated with their bleaching cannot be neglected.

scholarly journals Comparison Of Empirical Models For Estimating The Mineralization Potential Of Soil Nitrogen

2017 ◽  
Vol 7 (4) ◽  
pp. 1189-1202
Author(s):  
Zoubeir Bensid
Keyword(s):  
Nitrogen Mineralization ◽  
Goodness Of Fit ◽  
Empirical Models ◽  
The Other ◽  
Kinetics Model ◽  
Strong Positive Correlation ◽  
Mineralization Process ◽  
First Order ◽  
First Order Kinetics ◽  
Significant Difference

Modeling is an attempt to describe a natural event mathematically.  The modeling of N mineralization process has a dual interest, agronomical and ecological.  The objective of this study is to evaluate several mathematical models to describe the nitrogen mineralization process of soil samples. These samples were collected from 34 sites spatially distributed in the semi-arid region of El-Madher (the Aures area, north-east of Algeria). Using an auger, the systematic surveys have been carried out and composite samples of soils were collected in the field, and subjected to physical and chemical analyzes. In order to track the kinetic organic nitrogen mineralization, similar samples were collected and taken into cool boxes have been incubated in laboratory, sieved (2 mm) and stored at 4°C before use and then incubated at 28°C for 56 weeks. To facilate comparison, all results have been statistically analyzed, by nonlinear regression and analysis of variance method. Four empirical models were tested to fitt the value found experimentally. The linear kinetics model Nm=k t Ni, the single first-order kinetics model (MI) Nm = Ni e-kt + No (1 - e-kt), the double first-order and the exponential kinetics model (MII) Nm=Ni e-kt + No (1 - e-kt) + e-ht and the hyperbolic kinetics model (MH) Nm=NoH.t/(Tc+t) Ni were used to simulate the cumulative mineralized N (NH4+-N and NO3- -N) in the laboratory incubation. In order to test the performance and robustness of the different models three goodness of fit (coefficient of determination R2, Root Mean Square RMS and Mean Relative Error RMSE) were used. Moreover, the parameters obtained by the different models determined the predictions of nitrogen mineralization. The best results were obtained using the double first-order and exponential kinetics model. The results showed no significant difference between nitrogen mineralized for 56 weeks and nitrogen predicted by various models. However, the N predicted by the MII appears to be the best compared to other models. Indeed, the overestimation of nitrogen potentially mineralizable (N0) obtained by this model was relatively lower than other models. This has been confirmed by the study of multiple correlations between net mineral nitrogen and nitrogen predicted by each model. Thus, the results obtained showed a strong positive correlation between mineralized nitrogen values and those of nitrogen predicted by the different models. The correlation coefficients values indicate the folowing order MII (r = 0.878)> MI (r = 0.748)> MH (r = 0.709). The MII model has, therefore, highlighted that two pools of organic matter that mineralize simultaneously were detected in soil. One pool is stable and the other one is labile. One pool evolves with first-order kinetics and the other with exponential kinetics.

AN INDEPENDENT METHOD FOR OBTAINING THE ACTIVATION ENERGY OF THERMOLUMINESCENCE GLOW PEAKS

2004 ◽  
Vol 18 (20n21) ◽  
pp. 2877-2885 ◽  
Author(s):  
M. S. RASHEEDY
Keyword(s):  
Activation Energy ◽  
Glow Peak ◽  
Independent Method ◽  
Heating Rates ◽  
First Order ◽  
First Order Kinetics ◽  
General Order ◽  
Luminescence Process ◽  
The Common ◽  
Kinetics Order

The activation energy E (eV) of the first-order thermoluminescence (TL) glow peak is currently obtained using a two heating rates method. However, this method having the common drawback, that it assumes the first-order kinetics in the luminescence process. In the present work, an equation is suggested to determine the activation energy E (eV) of any glow peak, independent on the kinetics order of the process. To apply this method, three heating rates (β1,β2,β3), the corresponding peak temperatures (T1,T2,T3) and intensities (I1,I2,I3) of the isolated glow peaks are required. The applicability of the suggested method is demonstrated here by taking some numerically computed first-, second- and general-order TL glow peaks.

Efficient degradation of tetracycline by ultraviolet-based activation of peroxymonosulfate and persulfate

2019 ◽  
Vol 79 (5) ◽  
pp. 911-920 ◽  
Author(s):  
Jiamin Hu ◽  
Jing Zhang ◽  
Qingguo Wang ◽  
Qian Ye ◽  
Hao Xu ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Oxidative Capacity ◽  
Kinetics Model ◽  
Primary Radical ◽  
First Order ◽  
Uv Illumination ◽  
First Order Kinetics ◽  
Two Systems ◽  
Pseudo First Order ◽  
The Difference

Abstract In this study, the difference in oxidative capacity for removing antibiotics and the mechanism between the Cu(II)/peroxymonosulfate (PMS)/UV and Cu(II)/persulfate (PDS)/UV systems were compared under various conditions. The optimal Cu(II) concentration in the Cu(II)/PMS/UV system was 30 μM, and in the Cu(II)/PDS/UV system was 50 μM. With the PMS or PDS concentration increasing, higher tetracycline (TC) degradation in these two systems occurred. Investigation on the mechanism revealed that •OH was the primary radical in the Cu(II)/PMS/UV system, while SO4−• was the primary radical in the Cu(II)/PDS/UV system where •OH also played an important role. In these two systems, it was observed that Cu(I) was generated by PMS or PDS activated via UV illumination; however, oxygen alone could not promote TC removal. The degradation of TC was increased with the increasing pH level. In addition, TC degradation in the Cu(II)/PMS/UV system followed the pseudo-first-order kinetics model during the entire reaction period. It was found that the TC degradation kinetics in the Cu(II)/PDS/UV system can be divided into two parts (0 to 7 min and 10 to 50 min) and these two parts had good agreement with the pseudo-first-order kinetics model, respectively.

Sign in / Sign up

Export Citation Format

Share Document