Degradation and Mineralization of Pesticide Isoprocarb by Electro Fenton Process

Electro Fenton with volumic cathode consisting of granules of carbon graphite was applied to degrade the insecticide Isoprocarb in aqueous solutions. The effects of various factors including current intensity and pesticide initial concentration were investigated in order to obtain the best experimental conditions for its degradation and mineralization. Kinetic studies determined that the insecticide removal followed a pseudo first order. The absolute rate constant for the oxidation of Isoprocarb by hydroxyl radicals were determined as 3.32 × 109 L mol−1 s−1 by competitive kinetics method taking benzoic acid as reference compound. In this work, we have also studied the mineralization of aqueous solutions of this insecticide in term of total organic carbon (TOC). After 3 hours of electrolysis, and at I = 800 mA, more than 40 % of the organic carbon presented in the solution is mineralized. Various aromatic by-products, principally formed by oxidation of the pesticide, accompanied by hydroxylation of the aromatic cycle, have been identified. Thus, the oxidative opening of the aromatic ring leads to the formation of carboxylic acids and nitrate ions. The biodegradability of Isoprocarb is estimated by the measurement of its Biochemical Oxygen Demand (BOD5

Electro-Fenton Treatment of TNT in Aqueous Media in Presence of Cyclodextrin. Application to Ex-situ Treatment of Contaminated Soil

This preliminary study aims to examine, at laboratory scale, the mechanisms and performances provided by coupling the enhanced solubility abilities of cyclodextrin solutions for removal of 2,4,6-Trinitrotoluene (TNT) from contaminated soil with advanced oxidation processes (AOPs) that are regarded as the most effective approaches in treatment of wastewater contaminated with persistent and toxic organic pollutants. In recent years, different Fenton technologies have turned out to be quite appealing to eliminate recalcitrant organic pollutants. Among the different Fenton-like technologies currently available, indirect electrochemical treatment, namely electro-Fenton process, has appeared to be quite efficient in eliminating refractory organic compounds from aqueous media. HPLC/DAD was employed to monitor the TNT degradation and to identify the aromatic intermediates formed during the electro-Fenton oxidation of TNT. Absolute rate constant of TNT hydroxylation by hydroxyl radicals was determined as 2.06 × 10

Absolute rate constant and O(³P) yield for the O(¹D)+N₂O reaction in the temperature range 227 K to 719 K

The absolute rate constant for the reaction that is the major source of stratospheric NOx, O(1D)+N2O → products, has been determined in the temperature range 227 K to 719 K, and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.11)×10−10 cm3 s−1, and for temperatures greater than 450 K a marked decrease in rate constant was observed, with a rate constant of only (0.94±0.11)×10−10 cm3 s−1 at 719 K. The rate constants determined over the 227 K–400 K range show very low scatter and are significantly greater, by 20% at room temperature and 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1)C2H + O(1D) → CH(A) + CO and (kCL2)C2H + O(3P) → CH(A) + CO, both followed by CH(A) → CH(X) + hν, as kCL1(T)/kCL2(T)=(32.8T−3050)/(6.29T+398).

Absolute rate constant and O(³P) yield for the O(¹D)+N₂O reaction in the temperature range 227 K to 719 K

We have determined, in the temperature range 227 K to 719 K, the absolute rate constant for the reaction O(1D)+N2O → products and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.09)×10−10 cm3 s−1. For temperatures greater than 450 K a marked decrease in value was observed, with a rate constant of only (0.94±0.11)×10−10 cm3 s−1 at 719 K. The rate constants determined over the 227 K–400 K range show very low scatter and are significantly greater, by 20% at room temperature and by 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1) C2H+O(1D) → CH(A)+CO and (kCL2) C2H+O(3P) → CH(A)+CO, both followed by CH(A) → CH(X)+hν, as kCL1(T)/kCL2(T)=(32.8T−3050)/(6.29T+398).