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

This paper deals with the kinetic hydrolysis in aqueous media of Carzol or (E) 3-dimethylamino- methyleneaminophenyl-N-methylcarbamate hydrochloride. The Carzol is a bifunctional compound which belongs to the chemical families formamidine and carbamate. This work is carried out by UV Spectrophotometry. The successive determination of 3-aminophenyl-N-methylcarbamate and 3-aminophenol, as the mainproducts of the formamidine and the carbamate groups of Carzol hydrolysis gives evidence for the significant reactivity of this insecticide-acaricide in aqueous media. The obtained negative activation entropy ΔS≠ = - 32.39 J mol-1K-1 indicates a BAC2 mechanism involving bimolecular collapse of the formamidine group of Carzol. While, the obtained positive activation entropy ΔS≠ = +100.24J mol-1 K-1and the absence of basic general catalysis indicate an E1cB mechanism involving unimolecular collapse of the carbamate group of Carzol via a methylisocyanate intermediate.

Organic substances as pesticides, especially aromatic compounds are a major environmental concern. In the present work, solutions of Promecarb or 3-isopropyl-5-methylphenyl-N-methylcarbamate of pH = 3 have been degraded by electro Fenton process, using a volumic electrochemical reactor filled with carbon graphite. Effects of nature of material of cathode, initial concentration of insecticide and applied current on the kinetics of oxidative degradation and mineralization efficiency have been investigated. Kinetic analysis showed that the oxidation of Promecarb by hydroxyl radicals follows a reaction kinetic of pseudo first order. The absolute rate constant for Promecarb oxidation by hydroxyl radicals was determined as 10.88 × 10 9 L mol -1 s -1 by competitive kinetics method and benzoic acid was used as reference compound. Mineralization of this pesticide by hydroxyl radicals consists in its transformation to mineral products. The evolution of the mineralization during Promecarb treatment by electro Fenton process was followed by analysis of Total Organic Carbon TOC. Thus, after 3 hours of electrolysis and at I = 800 mA, more than 50% of the organic carbon present in the solution is mineralized. Several degradation products were formed during its electro Fenton treatment. These intermediates were identified using High Performance Liquid Chromatography HPLC, Ionic Chromatography IC and Liquid Chromatography -Mass Spectrometry LC-MS. Based on identification of aromatic intermediates and carboxylic acids, a plausible Promecarb mineralization pathway is proposed. Also, we realized the measurement of the Biochemical Oxygen Demand BOD 5 of insecticide solution after treatment by electro Fenton process, to evaluate its biodegradability.

The present paper deals with the degradation mechanism of the insecticide promecarb, or 3-isopropyl-5-methylphenyl- N-methylcarbamate, in aqueous media. The reaction kinetics have been investigated using UV spectrophotometry and reversed phase HPLC. The determination of 3-isopropyl-5-methylphenol as the main product of promecarb hydrolysis gives evidence for the significant reactivity of this insecticide in alkaline solution. The rate constants were determined following a proposed first-order kinetic model. The positive activation entropy obtained Δ S≠ = +66.82 J mol−1 K−1 and the absence of general basic catalysis indicates an E1cB mechanism involving unimolecular collapse of the promecarb via a methylisocyanate intermediate. These results were confirmed by the fact that promecarb fits well into Brønsted and Hammett plots obtained for a series of substituted N-methylcarbamates for which the decomposition in aqueous media was established to follow an E1cB mechanism.