Kinetic aspects and identification of by-products during the ozonation of bitertanol in agricultural wastewaters.

The degradation of bitertanol by ozone treatment is investigated. Solutions of bitertanol (8.4 µg mL(-1)) were prepared either by dissolution of the standard or by dilution of Gaucho Blé seed loading solution and then ozonated under different conditions. Evolution of the concentrations of bitertanol and its ozonation by-products in both solutions was monitored by HPLC-UV as a function of the treatment time for a concentration of 100 gm(-3) of ozone in the inlet gas. Bitertanol degradation was found to follow a pseudo-first order reaction in both cases. However, the rate of the reaction in diluted seed loading solution was much lower (0.19 vs. 0.27 min(-1) in standard solution) and was close to the reaction rate observed in the presence of a radical scavenger, tert-butanol (0.11 min(-1)). Thus, it may be suggested that additives present in the seed loading solution may play the role of radical scavengers. Study of ozone concentration in the inlet gas (from 25 to 100 gm(-3)) showed that ozone degradation is also a first-order reaction with respect to ozone. Four ozonation by-products were highlighted, collected and identified by HPLC coupled with an ion trap mass spectrometer using positive electrospray ionization mode. A degradation pathway of bitertanol was finally proposed.

Ozonation of imidacloprid in aqueous solutions: reaction monitoring and identification of degradation products.

This paper presents the degradation of imidacloprid by ozonation. Solutions of 39.0 µg/mL imidacloprid were prepared either by dissolution of standard or by dilution of Gaucho Blé(®) seed loading solution and then ozonated under different conditions. The concentration of imidacloprid and oxidation products in both solutions was monitored by HPLC-UV as a function of the treatment time for a concentration of 100g/m(3) of ozone in the inlet gas. No significant difference was observed: in both cases, imidacloprid degradation was a pseudo-first order reaction with similar reaction rates (0.129-0.147 min(-1)), degradation by-products with the same HPLC retention times were observed and their concentrations as a function of the treatment time followed a very similar trend. The study of ozone concentration in the inlet gas (from 25 to 100g/m(3)) showed that imidacloprid degradation is also a first-order reaction with respect to ozone. The ozonation by-products were then collected and identified by ESI(+)-MS. A degradation pathway of imidacloprid was finally proposed.

Development of a rapid determination of pesticides in coated seeds using a high-performance liquid chromatography-UV detection system.

For the determination of pesticides in coated seeds, this study compared two HPLC-UV methods, using a short column or a conventional column, as well as two extraction procedures, by ultrasonic extraction at room temperature or by pressurized liquid extraction (PLE). The comparison of selected column performances showed that the short column enabled the 3-fold reduction of analysis time (ca. 9 min vs 29 min) and eluent consumption (ca. 6.1 mL vs 20.8 mL) for the separation of five insecticides (bitertanol, fludioxonil, imidacloprid, metalaxyl-M and tefluthrin) and one bird repellent (anthraquinone) without altering peak resolutions. Recovery rates for pressurized liquid extraction at 120 degrees C were similar (between 84% and 102%) to those obtained by ultrasonication. Both methods were then applied for the extraction of loaded seeds. Rates for ultrasonic extraction at room temperature were lower (from 16% to 95%) than those observed for recovery tests, unlike PLE at 120 degrees C which showed good rates, ranging between 82% and 95%, for all the loaded pesticides.

Study of catalyzed ozonation for advanced treatment of pulp and paper mill effluents.

Ozonation and catalytic ozonation (TOCCATA process) were used as tertiary treatments of wastewaters from three different pulp and paper mills. Laboratory batch experiments were conducted to assess the efficiency of each oxidation system for removal of organic matter. The investigations measured ozone consumption rate, variations in chemical oxygen demand (COD), total organic carbon (TOC), suspended solids (SS) and molecular weight distribution with contact time. For conventional ozonation, ozone consumption rate was dependent on the nature of the effluent. Organic matter elimination occurred both by oxidation and precipitation. Precipitation played a major role on TOC removal varying with the effluent, and was responsible for production of high final SS concentrations. However, the effluent type did not affect the ozone consumption rate for TOCCATA-catalyzed reactions. Using TOCCATA, it was shown that organic matter was removed through steady conversion of organic carbon to carbon dioxide. Finally the two oxidation systems were compared with respect to their impact on molecular weight distribution. A total removal of the two initial fractions of compounds (high and low molecular weights) was observed with two effluents. With the third effluent, only the initial fraction of low molecular weight compounds was removed by the two oxidizing systems. The results showed that ozonation and TOCCATA-catalyzed ozonation could achieve removals of COD of 36-76%. Depending on the effluent type, the amount of ozone consumed per gram of COD removed was lower for conventional or for catalytic ozonation.