In this paper the spread-spectrum technique is applied to a resonant half-bridge inverter for dom... more In this paper the spread-spectrum technique is applied to a resonant half-bridge inverter for domestic induction heating in order to improve the electromagnetic interference (EMI). This technique has been successfully applied in switching mode power supplies (SMPS). Two different switching frequency modulation strategies are tested and the influence of different modulation parameters is analysed. Both simulation and experimental test bench
Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remov... more Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remove organic matter present in those wastes. The degradation process was followed by measuring the chemical oxygen demand (COD), and the total contents of phenolic and aromatic compounds. Reductions in COD were an average 6% and 20% in wastewaters diluted to 50% and 10% respectively. Average removal of aromatic compounds were 40% and 70% for both dilutions, while total phenolic content degradations was around 90% in all cases. An approximate kinetic study for design purposes was developed: the apparent kinetic constants for phenolic compounds are evaluated and correlated as a function of temperature and pH.
Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remov... more Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remove organic matter present in those wastes. The degradation process was followed by measuring the chemical oxygen demand (COD), and the total contents of phenolic and aromatic compounds. Reductions in COD were an average 6% and 20% in wastewaters diluted to 50% and 10% respectively. Average removal of aromatic compounds were 40% and 70% for both dilutions, while total phenolic content degradations was around 90% in all cases. An approximate kinetic study for design purposes was developed: the apparent kinetic constants for phenolic compounds are evaluated and correlated as a function of temperature and pH.
Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remov... more Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remove organic matter present in those wastes. The degradation process was followed by measuring the chemical oxygen demand (COD), and the total contents of phenolic and aromatic compounds. Reductions in COD were an average 6% and 20% in wastewaters diluted to 50% and 10% respectively. Average removal of aromatic compounds were 40% and 70% for both dilutions, while total phenolic content degradations was around 90% in all cases. An approximate kinetic study for design purposes was developed: the apparent kinetic constants for phenolic compounds are evaluated and correlated as a function of temperature and pH.
Chemical treatments of wastewaters from the olive industry are conducted by means of single UV ra... more Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen peroxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen peroxide plus UV radiation (photo-Fenton system). The single photochemical process produces a 35% removal of organic matter present measured as COD after 6 h of reaction, while the hydroxyl radicals enhance significantly this reduction with values in the range 41–76%. At the same time, a removal of aromatic compounds in the oxidation by single UV radiation and combined UV+H2O2 was obtained in the range 20–52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77–0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4 · g COD−1 obtained for the methane yield coefficient. A kinetic study was conducted using the Monod model, and rate constants ko in the range 0.061–0.015 min−1 achieved. This indicates that some inhibition effects by substances present take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory parameter and critical substrate concentration of inhibition, their values being k=0.205 min−1, n=18.8 and S*=20.1 g l−1 respectively. Finally, the anaerobic digestion of the chemically pretreated wastewaters increases the rate constant ko, as well as the methane yield coefficient, its value being 282 ml CH4 · g COD−1.
The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a freque... more The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton’s reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H2O2, and UV radiation plus Fenton’s reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.
Chemical treatments of wastewaters from the olive industry are conducted by means of single UV ra... more Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen peroxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen peroxide plus UV radiation (photo-Fenton system). The single photochemical process produces a 35% removal of organic matter present measured as COD after 6 h of reaction, while the hydroxyl radicals enhance significantly this reduction with values in the range 41–76%. At the same time, a removal of aromatic compounds in the oxidation by single UV radiation and combined UV+H2O2 was obtained in the range 20–52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77–0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4 · g COD−1 obtained for the methane yield coefficient. A kinetic study was conducted using the Monod model, and rate constants ko in the range 0.061–0.015 min−1 achieved. This indicates that some inhibition effects by substances present take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory parameter and critical substrate concentration of inhibition, their values being k=0.205 min−1, n=18.8 and S*=20.1 g l−1 respectively. Finally, the anaerobic digestion of the chemically pretreated wastewaters increases the rate constant ko, as well as the methane yield coefficient, its value being 282 ml CH4 · g COD−1.
The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition p... more The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition process using a polychromatic UV irradiation, and by an ozonation process. In the photodegradation process, the pH accelerated the decomposition rate and the approximate first-order rate constants were evaluated, with values between 0.16 ± 0.005 min−1 at pH=3 and 0.26 ± 0.007 min−1 at pH=9. A more rigorous kinetic study led to the determination of the quantum yields of the reaction, with values of 200 ±7 × 10−3 mol/Eins for pH=3 and 22 ± 1.1 × 10−3 mol/Eins for pH=9. In the ozonation process, the rate constants for the reaction between ozone and PCP were determined by means of a competition kinetics, with values in the range from 0.67 × 105 to 314 × 105 l/mol s. The specific rate constants for the un-dissociated and dissociated forms of PCP were also calculated. Finally, in both processes, the intermediate reaction products were identified, the most important being tetrachlorocatechol, tetrachlorohydroquinone and tetra-p-chlorobenzoquinone. Free chloride ion released, which was favored at high pHs, was also followed in both processes.
Chemical treatments of wastewaters from the olive industry are conducted by means of single UV ra... more Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen peroxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen peroxide plus UV radiation (photo-Fenton system). The single photochemical process produces a 35% removal of organic matter present measured as COD after 6 h of reaction, while the hydroxyl radicals enhance significantly this reduction with values in the range 41–76%. At the same time, a removal of aromatic compounds in the oxidation by single UV radiation and combined UV+H2O2 was obtained in the range 20–52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77–0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4 · g COD−1 obtained for the methane yield coefficient. A kinetic study was conducted using the Monod model, and rate constants ko in the range 0.061–0.015 min−1 achieved. This indicates that some inhibition effects by substances present take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory parameter and critical substrate concentration of inhibition, their values being k=0.205 min−1, n=18.8 and S*=20.1 g l−1 respectively. Finally, the anaerobic digestion of the chemically pretreated wastewaters increases the rate constant ko, as well as the methane yield coefficient, its value being 282 ml CH4 · g COD−1.
The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a freque... more The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton’s reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H2O2, and UV radiation plus Fenton’s reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.
The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol(4-CP), 2... more The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol(4-CP), 2,4-dichlorophenol (2-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)), which are environmental priority pollutants, is studied by means of single oxidants (hydrogen peroxide, UV radiation, Fenton's reagent and ozone at pH 2 and 9), and by the Advanced Oxidation Processes (AOPs) constituted by combinations of these oxidants (UV/H2O2, UV/Fenton's reagent and O3/UV). For all these reactions the degradation rates are evaluated by determining their first-order rate constants and the half-life times. Ozone is more reactive with higher substituted CPs while radicals react faster with those chlorophenols having lower number of chlorine atoms. The improvement in the decomposition levels reached by the combined processes, due to the generation of the very reactive hydroxyl radicals, in relation to the single oxidants is clearly demonstrated and evaluated by kinetic modeling.
The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a freque... more The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton’s reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H2O2, and UV radiation plus Fenton’s reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.
The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition p... more The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition process using a polychromatic UV irradiation, and by an ozonation process. In the photodegradation process, the pH accelerated the decomposition rate and the approximate first-order rate constants were evaluated, with values between 0.16 ± 0.005 min−1 at pH=3 and 0.26 ± 0.007 min−1 at pH=9. A more rigorous kinetic study led to the determination of the quantum yields of the reaction, with values of 200 ±7 × 10−3 mol/Eins for pH=3 and 22 ± 1.1 × 10−3 mol/Eins for pH=9. In the ozonation process, the rate constants for the reaction between ozone and PCP were determined by means of a competition kinetics, with values in the range from 0.67 × 105 to 314 × 105 l/mol s. The specific rate constants for the un-dissociated and dissociated forms of PCP were also calculated. Finally, in both processes, the intermediate reaction products were identified, the most important being tetrachlorocatechol, tetrachlorohydroquinone and tetra-p-chlorobenzoquinone. Free chloride ion released, which was favored at high pHs, was also followed in both processes.
In this paper the spread-spectrum technique is applied to a resonant half-bridge inverter for dom... more In this paper the spread-spectrum technique is applied to a resonant half-bridge inverter for domestic induction heating in order to improve the electromagnetic interference (EMI). This technique has been successfully applied in switching mode power supplies (SMPS). Two different switching frequency modulation strategies are tested and the influence of different modulation parameters is analysed. Both simulation and experimental test bench
Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remov... more Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remove organic matter present in those wastes. The degradation process was followed by measuring the chemical oxygen demand (COD), and the total contents of phenolic and aromatic compounds. Reductions in COD were an average 6% and 20% in wastewaters diluted to 50% and 10% respectively. Average removal of aromatic compounds were 40% and 70% for both dilutions, while total phenolic content degradations was around 90% in all cases. An approximate kinetic study for design purposes was developed: the apparent kinetic constants for phenolic compounds are evaluated and correlated as a function of temperature and pH.
Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remov... more Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remove organic matter present in those wastes. The degradation process was followed by measuring the chemical oxygen demand (COD), and the total contents of phenolic and aromatic compounds. Reductions in COD were an average 6% and 20% in wastewaters diluted to 50% and 10% respectively. Average removal of aromatic compounds were 40% and 70% for both dilutions, while total phenolic content degradations was around 90% in all cases. An approximate kinetic study for design purposes was developed: the apparent kinetic constants for phenolic compounds are evaluated and correlated as a function of temperature and pH.
Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remov... more Chemical oxidation by ozone of the wastewaters from the olive oil process is carried out to remove organic matter present in those wastes. The degradation process was followed by measuring the chemical oxygen demand (COD), and the total contents of phenolic and aromatic compounds. Reductions in COD were an average 6% and 20% in wastewaters diluted to 50% and 10% respectively. Average removal of aromatic compounds were 40% and 70% for both dilutions, while total phenolic content degradations was around 90% in all cases. An approximate kinetic study for design purposes was developed: the apparent kinetic constants for phenolic compounds are evaluated and correlated as a function of temperature and pH.
Chemical treatments of wastewaters from the olive industry are conducted by means of single UV ra... more Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen peroxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen peroxide plus UV radiation (photo-Fenton system). The single photochemical process produces a 35% removal of organic matter present measured as COD after 6 h of reaction, while the hydroxyl radicals enhance significantly this reduction with values in the range 41–76%. At the same time, a removal of aromatic compounds in the oxidation by single UV radiation and combined UV+H2O2 was obtained in the range 20–52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77–0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4 · g COD−1 obtained for the methane yield coefficient. A kinetic study was conducted using the Monod model, and rate constants ko in the range 0.061–0.015 min−1 achieved. This indicates that some inhibition effects by substances present take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory parameter and critical substrate concentration of inhibition, their values being k=0.205 min−1, n=18.8 and S*=20.1 g l−1 respectively. Finally, the anaerobic digestion of the chemically pretreated wastewaters increases the rate constant ko, as well as the methane yield coefficient, its value being 282 ml CH4 · g COD−1.
The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a freque... more The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton’s reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H2O2, and UV radiation plus Fenton’s reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.
Chemical treatments of wastewaters from the olive industry are conducted by means of single UV ra... more Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen peroxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen peroxide plus UV radiation (photo-Fenton system). The single photochemical process produces a 35% removal of organic matter present measured as COD after 6 h of reaction, while the hydroxyl radicals enhance significantly this reduction with values in the range 41–76%. At the same time, a removal of aromatic compounds in the oxidation by single UV radiation and combined UV+H2O2 was obtained in the range 20–52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77–0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4 · g COD−1 obtained for the methane yield coefficient. A kinetic study was conducted using the Monod model, and rate constants ko in the range 0.061–0.015 min−1 achieved. This indicates that some inhibition effects by substances present take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory parameter and critical substrate concentration of inhibition, their values being k=0.205 min−1, n=18.8 and S*=20.1 g l−1 respectively. Finally, the anaerobic digestion of the chemically pretreated wastewaters increases the rate constant ko, as well as the methane yield coefficient, its value being 282 ml CH4 · g COD−1.
The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition p... more The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition process using a polychromatic UV irradiation, and by an ozonation process. In the photodegradation process, the pH accelerated the decomposition rate and the approximate first-order rate constants were evaluated, with values between 0.16 ± 0.005 min−1 at pH=3 and 0.26 ± 0.007 min−1 at pH=9. A more rigorous kinetic study led to the determination of the quantum yields of the reaction, with values of 200 ±7 × 10−3 mol/Eins for pH=3 and 22 ± 1.1 × 10−3 mol/Eins for pH=9. In the ozonation process, the rate constants for the reaction between ozone and PCP were determined by means of a competition kinetics, with values in the range from 0.67 × 105 to 314 × 105 l/mol s. The specific rate constants for the un-dissociated and dissociated forms of PCP were also calculated. Finally, in both processes, the intermediate reaction products were identified, the most important being tetrachlorocatechol, tetrachlorohydroquinone and tetra-p-chlorobenzoquinone. Free chloride ion released, which was favored at high pHs, was also followed in both processes.
Chemical treatments of wastewaters from the olive industry are conducted by means of single UV ra... more Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen peroxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen peroxide plus UV radiation (photo-Fenton system). The single photochemical process produces a 35% removal of organic matter present measured as COD after 6 h of reaction, while the hydroxyl radicals enhance significantly this reduction with values in the range 41–76%. At the same time, a removal of aromatic compounds in the oxidation by single UV radiation and combined UV+H2O2 was obtained in the range 20–52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77–0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4 · g COD−1 obtained for the methane yield coefficient. A kinetic study was conducted using the Monod model, and rate constants ko in the range 0.061–0.015 min−1 achieved. This indicates that some inhibition effects by substances present take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory parameter and critical substrate concentration of inhibition, their values being k=0.205 min−1, n=18.8 and S*=20.1 g l−1 respectively. Finally, the anaerobic digestion of the chemically pretreated wastewaters increases the rate constant ko, as well as the methane yield coefficient, its value being 282 ml CH4 · g COD−1.
The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a freque... more The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton’s reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H2O2, and UV radiation plus Fenton’s reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.
The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol(4-CP), 2... more The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol(4-CP), 2,4-dichlorophenol (2-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)), which are environmental priority pollutants, is studied by means of single oxidants (hydrogen peroxide, UV radiation, Fenton's reagent and ozone at pH 2 and 9), and by the Advanced Oxidation Processes (AOPs) constituted by combinations of these oxidants (UV/H2O2, UV/Fenton's reagent and O3/UV). For all these reactions the degradation rates are evaluated by determining their first-order rate constants and the half-life times. Ozone is more reactive with higher substituted CPs while radicals react faster with those chlorophenols having lower number of chlorine atoms. The improvement in the decomposition levels reached by the combined processes, due to the generation of the very reactive hydroxyl radicals, in relation to the single oxidants is clearly demonstrated and evaluated by kinetic modeling.
The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a freque... more The degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), a frequently used carbamate derivative pesticide that is considered a priority pollutant, is carried out in batch reactors by means of single oxidants: ozone, UV radiation and Fenton’s reagent; and by the advanced oxidation processes (AOPs) constituted by combinations of ozone plus UV radiation, UV radiation plus H2O2, and UV radiation plus Fenton’s reagent (photo-Fenton system). For all these reactions, the apparent pseudo-first-order rate constants are evaluated in order to compare the efficiency of each process. In addition and by means of a competition kinetic model, the rate constants for the reaction of carbofuran with ozone and with hydroxyl radicals are also determined. The improvement in the decomposition levels of carbofuran reached by the combined processes in relation to the single oxidants, due to the generation of the very reactive hydroxyl radicals, is also established in every process. For the oxidant concentrations applied, the most effective process in removing carbofuran was the photo-Fenton system.
The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition p... more The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition process using a polychromatic UV irradiation, and by an ozonation process. In the photodegradation process, the pH accelerated the decomposition rate and the approximate first-order rate constants were evaluated, with values between 0.16 ± 0.005 min−1 at pH=3 and 0.26 ± 0.007 min−1 at pH=9. A more rigorous kinetic study led to the determination of the quantum yields of the reaction, with values of 200 ±7 × 10−3 mol/Eins for pH=3 and 22 ± 1.1 × 10−3 mol/Eins for pH=9. In the ozonation process, the rate constants for the reaction between ozone and PCP were determined by means of a competition kinetics, with values in the range from 0.67 × 105 to 314 × 105 l/mol s. The specific rate constants for the un-dissociated and dissociated forms of PCP were also calculated. Finally, in both processes, the intermediate reaction products were identified, the most important being tetrachlorocatechol, tetrachlorohydroquinone and tetra-p-chlorobenzoquinone. Free chloride ion released, which was favored at high pHs, was also followed in both processes.
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Papers by Juan Acero