Pretreatment of pesticide wastewater by photocatalytic oxidation

1997 ◽  
Vol 36 (2-3) ◽  
pp. 117-122 ◽  
Author(s):  
Ming-Chun Lu ◽  
Jong-Nan Chen
Keyword(s):  
Organic Carbon ◽  
Photocatalytic Oxidation ◽  
Parent Compound ◽  
Order Reaction ◽  
Toxic Chemicals ◽  
Reaction Products ◽  
Model Compounds ◽  
First Order ◽  
Different Characteristics ◽  
Complete Mineralization

The toxic chemicals, 2,4-D (a herbicide) and propoxur (an insecticide), were used as the model compounds in these experiments. Total organic carbon analyzer was used to assess the efficiency of photocatalytic mineralization. Microtox bioassay was employed in evaluating the toxicity of solutions treated by photocatalysis. Ultraviolet absorption spectra were also used for showing the different characteristics of the compounds undergoing photocatalytic oxidation. Results show that propoxur is less degradable than 2,4-D, and the photomineralization of these pesticides follows a behavior of first-order reaction. Products of 2,4-D and propoxur are more toxic than the parent compound after partial photodegradation. This shows that complete mineralization is necessary for total detoxification of these pesticides. In other words, toxicity is an important criteria in assessing the pretreatment process.

Interactions of hypochlorite ion and humic acid: photolytic and photocatalytic pathways

2001 ◽  
Vol 44 (5) ◽  
pp. 205-210 ◽  
Author(s):  
D. Gonenç ◽  
M. Bekbolet
Keyword(s):  
Humic Acid ◽  
Reaction Kinetics ◽  
Removal Efficiency ◽  
Photocatalytic Oxidation ◽  
Removal Rate ◽  
Order Reaction ◽  
First Order Reaction ◽  
Acid Oxidation ◽  
First Order ◽  
Toc Removal

Photolytic and photocatalytic interactions of hypochlorite ion and humic acid are investigated under various conditions. Humic acid oxidation by aqueous chlorine under dark conditions are expressed in terms of first order reaction kinetics. Upon irradiation (300 nm < λ < 400 nm), photolysis of aqueous chlorine affect the removal efficiency of humic acid via oxidation. TiO2 sensitised photocatalytic oxidation conditions reveal an increase in the TOC removal rate of humic acid in the presence of aqueous chlorine. Under the specified conditions, increasing the photocatalyst loading up to 1.0 mg/mL markedly increase the TOC removal rate.

scholarly journals Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

2005 ◽  
Vol 5 (9) ◽  
pp. 2497-2517 ◽  
Author(s):  
B. Aumont ◽  
S. Szopa ◽  
S. Madronich
Keyword(s):  
Organic Carbon ◽  
Gas Phase ◽  
Organic Compounds ◽  
Parent Compound ◽  
Oxidation Products ◽  
Gradual Change ◽  
Reaction Products ◽  
Test Species ◽  
Lack Of Information ◽  
Data Processing Tool

Abstract. Organic compounds emitted in the atmosphere are oxidized in complex reaction sequences that produce a myriad of intermediates. Although the cumulative importance of these organic intermediates is widely acknowledged, there is still a critical lack of information concerning the detailed composition of the highly functionalized secondary organics in the gas and condensed phases. The evaluation of their impacts on pollution episodes, climate, and the tropospheric oxidizing capacity requires modelling tools that track the identity and reactivity of organic carbon in the various phases down to the ultimate oxidation products, CO and CO2. However, a fully detailed representation of the atmospheric transformations of organic compounds involves a very large number of intermediate species, far in excess of the number that can be reasonably written manually. This paper describes (1) the development of a data processing tool to generate the explicit gas-phase oxidation schemes of acyclic hydrocarbons and their oxidation products under tropospheric conditions and (2) the protocol used to select the reaction products and the rate constants. Results are presented using the fully explicit oxidation schemes generated for two test species: n-heptane and isoprene. Comparisons with well-established mechanisms were performed to evaluate these generated schemes. Some preliminary results describing the gradual change of organic carbon during the oxidation of a given parent compound are presented.

scholarly journals Decontamination performance of air filter paper impregnated with zirconium hydroxide on sulfur mustard

2021 ◽  
Vol 267 ◽  
pp. 02063
Author(s):  
Xingqi Huang ◽  
Ting Zhao ◽  
Chunxiao Yan ◽  
Yanren Jin ◽  
Yue Wu ◽  
...  
Keyword(s):  
Filter Paper ◽  
Degradation Rate ◽  
Sulfur Mustard ◽  
Filtration Efficiency ◽  
Zirconium Hydroxide ◽  
Order Reaction ◽  
Reaction Products ◽  
Air Filter ◽  
First Order ◽  
Before And After

Using zirconium hydroxide as a decontaminant, a kind of self-decontaminating air filter paper that can effectively degrade HD was successfully prepared by impregnating. The morphology and filtration efficiency of the filter paper before and after immersing were compared. The filtration efficiency increased linearly and slowly, with the regression equation: η=0.0001L+99.971. The liquid-solid decontamination reaction of HD on zirconium hydroxide powder and self-decontaminating filter paper conformed to the kinetic of quasi-first-order reaction and found that half-lives were 0.4 h and 2.1 h respectively. Good degradation performance for HD was exhibited and the degradation rate reached more than 99 % in 12 hours. Reaction products were analysed by GC-MS, which displayed that HD was decomposed through the substitution of chlorine and the elimination of H on α-C. The ultimate decontamination products were thiodiglycol and 2-hydroxyethyl vinyl sulfide without erosive toxicity.

Removal of Chlorophenols from Water by Photocatalytic Oxidation

1991 ◽  
Vol 23 (1-3) ◽  
pp. 377-387 ◽  
Author(s):  
J. M. Tseng ◽  
C. P. Huang
Keyword(s):  
Organic Compounds ◽  
Photocatalytic Oxidation ◽  
Uv Light ◽  
Maximum Level ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Mineral Acids ◽  
Positive Holes

Photocatalyst, TiO2, upon irradiation with uv light produces electrons and positive holes. The positive holes are strong oxidation agents that can oxidize organic compounds such as chlorophenol to mineral acids e.g. HC1 and CO2. Factors such as pH, chlorophenol concentration, concentration of TiO2 and inorganic electrolytes that may affect the oxidation of chlorophenol were investigated. The rate of the chlorophenol oxidation follows a first order reaction with respect to the chlorophenol concentration and independent of pH. The rate increases with concentration of TiO2, reaches a maximum level at 3 g/L then decreases to a constant value upon further increase in TiO2. Increasing the degree of chlorination appears to increase the extent and the rate of oxidation. For mono-chlorophenols the extent of oxidation follows: 4-chloro > 3-chloro > 2-chloro phenol. For dichlorophenols, the order is 2,6-dichloro ≈ 2,5-dichloro > 2,4-dichloro≈ 2,3-dichlorophenol. For symmetrical chlorophenols, the oxidation increases in the order: 4-chloro > 2,5-dichloro > 2,4,6-trichlorophenol. Pentachlorophenol is rapidly decomposed but the extent of oxidation is not complete.

scholarly journals Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

2005 ◽  
Vol 5 (1) ◽  
pp. 703-754 ◽  
Author(s):  
B. Aumont ◽  
S. Szopa ◽  
S. Madronich
Keyword(s):  
Organic Carbon ◽  
Gas Phase ◽  
Organic Compounds ◽  
Parent Compound ◽  
Oxidation Products ◽  
Gradual Change ◽  
Reaction Products ◽  
Test Species ◽  
Lack Of Information ◽  
Data Processing Tool

Abstract. Organic compounds emitted in the atmosphere are oxidized in complex reaction sequences that produce a myriad of intermediates. Although the cumulative importance of these organic intermediates is widely acknowledged, there is still a critical lack of information concerning the detailed composition of the highly functionalized secondary organics in the gas and condensed phases. The evaluation of their impacts on pollution episodes, climate, and the tropospheric oxidizing capacity requires modelling tools that track the identity and reactivity of organic carbon in the various phases down to the ultimate oxidation products, CO and CO2. However, a fully detailed representation of the atmospheric transformations of organic compounds involves a very large number of intermediate species, far in excess of the number that can be reasonably written manually. This paper describes (1) the development of a data processing tool to generate the explicit gas-phase oxidation schemes of organic compounds under tropospheric conditions and (2) the protocol used to select the reaction products and the rate constants. Results are presented using the fully explicit oxidation schemes generated for two test species: n-heptane and isoprene. Comparisons with well-established mechanisms were performed to evaluate these generated schemes. Some preliminary results describing the gradual change of organic carbon during the oxidation of a given parent compound are presented.

Vulcanization of Elastomers. 30. Kinetics of the Decrease of Sulfur Concentration during Vulcanization

1961 ◽  
Vol 34 (2) ◽  
pp. 606-628 ◽  
Author(s):  
Walter Scheele ◽  
Martin Cherubim
Keyword(s):  
Initial Rate ◽  
Order Reaction ◽  
Usual Sense ◽  
Complex Nature ◽  
Reaction Products ◽  
Sulfur Concentration ◽  
First Order ◽  
Synthetic Rubber ◽  
Kinetics Of ◽  
Characteristic Trend

Abstract The present discussion deals with the explanation and critical analysis of the kinetics of the decrease in concentration of sulfur in accelerated and unaccelerated vulcanizations of natural and synthetic rubber. A marked distinction is made between the time law and the dependence on concentration of the rate of decrease of sulfur, since there is lack of agreement between them, both in accelerated and unaccelerated vulcanizations, which indicates the complex nature of vulcanization. In unaccelerated vulcanization, the sulfur concentration drops, at all temperatures and independent of the concentration, according to a time law with exponent n=0.6. On the other hand, the dependence on concentration of the initial rate of sulfur decrease proceeds according to a first order reaction. These relations make it seem probable that sulfur decrease involves a process which is catalyzed by reaction products. In accelerated vulcanization, the reduction of concentration of sulfur also is expressed by a time law with the exponent n<1, and this too is independent of temperature and concentration of reactants (sulfur and accelerator). However, the concentration dependence of the rate of sulfur decrease cannot be expressed by a power law, so that we find no order of reaction in the usual sense. We attempt to explain the characteristic trend of the initial rate of sulfur decrease with sulfur concentration at constant accelerator content, or with accelerator concentration at constant sulfur content, by assuming that the vulcanization takes place through intermediate compounds. The pertinent theoretical conceptions are disclosed and critically examined and the attempt is made to show the extent to which they may be brought into accord with the experimental data.

scholarly journals Photoelectrocatalytical degradation of basic blue 41 dye using nanoporous semiconductor of Ti/TiO2

2018 ◽  
Vol 39 (4) ◽  
pp. 27
Author(s):  
Luciano Evangelista Fraga ◽  
Maria Valnice Boldrin Zanoni
Keyword(s):  
Organic Carbon ◽  
Rate Constant ◽  
Initial Rate ◽  
Order Reaction ◽  
Pseudo First Order Reaction ◽  
Synthetic Fibers ◽  
First Order ◽  
Total Organic Carbon Removal ◽  
Pseudo First Order ◽  
A Current

The present work investigates the photoelectrocatalytical degradation Basic Blue 41 (BB 41) largely applied to dye synthetic fibers, using a semiconductor Ti/TiO2 as photoanode. 100% of degradation of 8.33 10-5 mol L-1 dye in 0.1 mol L−1 Na2SO4, pH 2 was obtained under current density of 0.40 mA cm−2 and irradiation UV after 60 min of treatment and 80% of total organic carbon removal. The oxidation follows pseudo-first order reaction with initial rate constant of -0,040 mim-1 and a current efficiency of 51%. The results are superior the conventional photocatalysis in the same conditions without the polarization of the photoanode that takes to 65% of mineralization under initial rate constant -0,024 min-1.

Leaching Kinetics of Atrazine and Inorganic Chemicals in Tilled and Orchard Soils

2014 ◽  
Vol 28 (2) ◽  
pp. 231-237 ◽  
Author(s):  
Lech W. Szajdak ◽  
Jerzy Lipiec ◽  
Anna Siczek ◽  
Artur Nosalewicz ◽  
Urszula Majewska
Keyword(s):  
Reaction Rate ◽  
Inorganic Compounds ◽  
Model Performance ◽  
Order Reaction ◽  
First Order Reaction ◽  
Order Kinetic ◽  
Time Data ◽  
First Order ◽  
Concentration Changes ◽  
Reaction Constants

Abstract The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K+1, Fe+3, Mg+2, Mn+2, NH4 +, NO3 - and PO4 -3) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.

The Kinetics of Glucose Decomposition with Sulfate Reduction in the Anaerobic Fluidized Bed Reactor

1993 ◽  
Vol 28 (2) ◽  
pp. 135-144 ◽  
Author(s):  
S. Matsui ◽  
R. Ikemoto Yamamoto ◽  
Y. Tsuchiya ◽  
B. Inanc
Keyword(s):  
Sulfate Reduction ◽  
Fluidized Bed ◽  
Kinetic Equations ◽  
Fluidized Bed Reactor ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Glucose Decomposition ◽  
Reaction Equations ◽  
Kinetics Of

Using a fluidized bed reactor, experiments on glucose decomposition with and without sulfate reduction were conducted. Glucose in the reactor was mainly decomposed into lactate and ethanol. Lactate was mainly decomposed into propionate and acetate, while ethanol was decomposed into propionate, acetate, and hydrogen. Sulfate reduction was not involved in the decomposition of glucose, lactate, and ethanol, but was related to propionate and acetate decomposition. The stepwise reactions were modeled using either a Monod expression or first order reaction kinetics in respect to the reactions. The coefficients of the kinetic equations were determined experimentally. The modified Monod and first order reaction equations were effective at predicting concentrations of glucose, lactate, ethanol, propionate, acetate, and sulfate along the beight of the reactor. With sulfate reduction, propionate was decomposed into acetate, while without sulfate reduction, accumulation of propionate was observed in the reactor. Sulfate reduction accelerated propionate conversion into acetate by decreasing the hydrogen concentration.

Complete monotonicity of entropy production in chemical reaction

1981 ◽  
Vol 46 (2) ◽  
pp. 452-456
Author(s):  
Milan Šolc
Keyword(s):  
Entropy Production ◽  
Equilibrium Constant ◽  
Chemical Reaction ◽  
Relative Entropy ◽  
Order Reaction ◽  
Complete Monotonicity ◽  
First Order Reaction ◽  
First Order ◽  
Completely Monotonic ◽  
Derivatives Of

The successive time derivatives of relative entropy and entropy production for a system with a reversible first-order reaction alternate in sign. It is proved that the relative entropy for reactions with an equilibrium constant smaller than or equal to one is completely monotonic in the whole definition interval, and for reactions with an equilibrium constant larger than one this function is completely monotonic at the beginning of the reaction and near to equilibrium.

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