The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Juan J. Rodriguez - One of the best experts on this subject based on the ideXlab platform.
-
aqueous phase hydrodechlorination of Chlorophenols with pillared clays supported pt pd and rh catalysts
Applied Catalysis B-environmental, 2014Co-Authors: C B Molina, Jose A Casas, A H Pizarro, Juan J. RodriguezAbstract:Abstract Pt, Pd and Rh catalysts supported on pillared clays have been prepared and tested in the hydrodechlorination (HDC) of Chlorophenols with H2. Different catalyst reduction temperatures, metal loadings and reaction temperatures were tested. Pd and Rh catalysts showed the highest activity with 4-chlorophenol as target compound allowing complete dechlorination at mild operating conditions (25 °C and atmospheric pressure) with negligible metal leaching. The kinetics of 4-CP hydrodechlorination with these catalysts has been analyzed from the corresponding proposed pathways. The stability of the catalysts was checked in long-term experiments being the most stable those of Pd and Rh with no more of 5% activity loss after 300 h on stream. Other Chlorophenols (2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol) were also tested as target pollutants with the Rh catalyst yielding complete conversion in all cases. Chlorinated compounds were not found as final products.
-
a ferromagnetic γ alumina supported iron catalyst for cwpo application to Chlorophenols
Applied Catalysis B-environmental, 2013Co-Authors: Macarena Munoz, Jose A Casas, Zahara M De Pedro, N Menendez, Juan J. RodriguezAbstract:Abstract A ferromagnetic γ-Al 2 O 3 -supported iron catalyst has been prepared and its activity and stability in catalytic wet peroxide oxidation (CWPO) have been compared with those of a previous iron-based conventional catalyst using the same support. Both catalysts were characterized by nitrogen adsorption–desorption isotherms, ICP, TXRF, XRD, XPS, elemental analysis and Mossbauer spectroscopy. The behavior of these catalysts in CWPO of Chlorophenols has been related with the nature of the dominant iron species (magnetite or hematite). The results showed that the magnetic catalyst improved significantly the decomposition of H 2 O 2 leading to an increased degradation and mineralization of Chlorophenols. Complete conversion of those target pollutants and more than 75% TOC reduction were achieved after 4 h under stoichiometric H 2 O 2 dose, 100 mg L −1 initial chlorophenol concentration, 1 g L −1 catalyst, pH 3 and 50 °C temperature. Moreover, complete dechlorination of all the Chlorophenols tested was achieved, being the residual organic by-products short-chain acids without significance in terms of ecotoxicity. The catalyst showed a remarkable stability in long-term continuous experiments with limited Fe leaching, below 5% of the initial loading after 100 h on stream. An additional clear advantage of the new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field.
-
Inhibition of methanogenesis by Chlorophenols: a kinetic approach
New Biotechnology, 2012Co-Authors: Daniel Puyol, Juan J. Rodriguez, J. L. Sanz, Angel F. MohedanoAbstract:Chlorophenols exert a crucial effect on the methanogenesis, considerably reducing both maximum methane potential and methanogenic rates. However, there is not enough information about the kinetic mechanism of Chlorophenols toxicity on the methanogenesis, which is a key aspect for the control of the anaerobic digesters because of the sensitivity and the potential for energy recovery derived from methane release. The International Water Association-Anaerobic Digestion Model No. 1 (IWA-ADM1) can be adapted to a wide range of situations by updating or changing the equations in the model. The present study proposes a general kinetic model for methanogenesis. This model has been applied to predict the inhibition of methanogenesis by Chlorophenols, and it can be used for updating the IWA-ADM1 when treating inhibitory compounds. The model was calibrated and validated using a wide broad of experimental sets of data of methane production by granular sludge in the presence of 2,4-dichlorophenol (24DCP), 2,4,6-trichlorophenol (246TCP) and pentachlorophenol (PCP) in batch assays. A lag-phase of the effect of Chlorophenols on the methanogenesis by non-adapted sludge was detected and modeled by the kinetic model proposed. In addition, the inhibitory effect of PCP was more pronounced on the acetoclastic methanogenesis than on the hydrogenotrophic one. Non-competitive and uncompetitive inhibition types were detected using 24DCP and 246TCP, whereas a suicide or irreversible inhibition type was observed in the case of PCP. Values of inhibition constants considerably varied depending on the chlorophenol used, between 45 mg 24DCP L−1, 41–51 mg 246TCP L−1 and 0.9–7.8 mg PCP L−1. The higher toxicity of PCP is related with its hydrophobicity, which was determined by adsorption tests and using partition coefficients n-octanol/water. Modeling was accompanied by high statistical support in all cases, which confirmed the validation of the model proposed.
-
treatment of Chlorophenols bearing wastewaters through hydrodechlorination using pd activated carbon catalysts
Carbon, 2004Co-Authors: L Calvo, Angel F. Mohedano, Jose A Casas, M A Gilarranz, Juan J. RodriguezAbstract:Abstract The catalytic hydrodechlorination of 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol in aqueous solution over Pd/activated carbon catalysts (0.5% w/w Pd) was studied in a fixed bed reactor. The reactor was fed with a 100 mg/l solution of chlorophenol and a H2/N2 (1:1) gas stream. The ranges studied for temperature, pressure and space–time were 25–100 °C, 1.8–6.0 bar and 14–55 kg h/mol, respectively. A commercial and some home-made catalysts were tested. The carbon supports were subjected to oxidation with nitric acid and sodium persulfate. Chlorophenols conversion was found to peak for pressure values ≈2.4 bar. In these conditions, an increase of reaction temperature increases conversion. In the runs carried out at high space–time both the reactants conversion and the selectivity towards end chain reaction products was enhanced. The oxidation of the carbon support with nitric acid prior to impregnation improves conversion. At the optimum conditions (2.4 bar, 75 °C and nitric acid oxidation of carbon support) conversion values over 95% were reached for all Chlorophenols. As a result of this treatment the toxicity of the initial solutions was reduced by more than 90%.
Javier F Rubio - One of the best experts on this subject based on the ideXlab platform.
-
rate constants for the reactions of ozone with Chlorophenols in aqueous solutions
Journal of Hazardous Materials, 2000Co-Authors: Javier F Benitez, J Beltranheredia, Juan L Acero, Javier F RubioAbstract:Abstract The oxidation by ozone of several Chlorophenols (CPs): 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, tetracholorocatechol (3,4,5,6-tetrachloro-2-hydroxy phenol) and 4-chloroguaiacol (4-chloro-2-methoxy phenol), is studied in order to provide values of the overall rate constant for the reaction between ozone and these Chlorophenols. Single ozonation experiments of 4-chlorophenol were conducted in an homogeneous system, and ozonation reactions of CP mixtures were performed in a heterogeneous system, leading to the evaluation of the overall ozonation rate constants in acidic aqueous solutions. These second order rate constants increase several order of magnitude with the pH as does the degree of deprotonation of the dissolved compounds (i.e. from 103 to 109 l/(mol s) for different CPs). The specific rate constants for the ozonation of the non-dissociated and dissociated forms of the studied CPs are also determined and reported. The values obtained allow calculation of the overall rate constants and prediction of the reactivities of the several CPs at different operating conditions in the whole range of pH.
-
contribution of free radicals to Chlorophenols decomposition by several advanced oxidation processes
Chemosphere, 2000Co-Authors: Javier F Benitez, J Beltranheredia, Juan L Acero, Javier F RubioAbstract:Abstract 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/H 2 O 2 , UV/Fenton's reagent and O 3 /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 OH 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.
Jose A Casas - One of the best experts on this subject based on the ideXlab platform.
-
aqueous phase hydrodechlorination of Chlorophenols with pillared clays supported pt pd and rh catalysts
Applied Catalysis B-environmental, 2014Co-Authors: C B Molina, Jose A Casas, A H Pizarro, Juan J. RodriguezAbstract:Abstract Pt, Pd and Rh catalysts supported on pillared clays have been prepared and tested in the hydrodechlorination (HDC) of Chlorophenols with H2. Different catalyst reduction temperatures, metal loadings and reaction temperatures were tested. Pd and Rh catalysts showed the highest activity with 4-chlorophenol as target compound allowing complete dechlorination at mild operating conditions (25 °C and atmospheric pressure) with negligible metal leaching. The kinetics of 4-CP hydrodechlorination with these catalysts has been analyzed from the corresponding proposed pathways. The stability of the catalysts was checked in long-term experiments being the most stable those of Pd and Rh with no more of 5% activity loss after 300 h on stream. Other Chlorophenols (2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol) were also tested as target pollutants with the Rh catalyst yielding complete conversion in all cases. Chlorinated compounds were not found as final products.
-
a ferromagnetic γ alumina supported iron catalyst for cwpo application to Chlorophenols
Applied Catalysis B-environmental, 2013Co-Authors: Macarena Munoz, Jose A Casas, Zahara M De Pedro, N Menendez, Juan J. RodriguezAbstract:Abstract A ferromagnetic γ-Al 2 O 3 -supported iron catalyst has been prepared and its activity and stability in catalytic wet peroxide oxidation (CWPO) have been compared with those of a previous iron-based conventional catalyst using the same support. Both catalysts were characterized by nitrogen adsorption–desorption isotherms, ICP, TXRF, XRD, XPS, elemental analysis and Mossbauer spectroscopy. The behavior of these catalysts in CWPO of Chlorophenols has been related with the nature of the dominant iron species (magnetite or hematite). The results showed that the magnetic catalyst improved significantly the decomposition of H 2 O 2 leading to an increased degradation and mineralization of Chlorophenols. Complete conversion of those target pollutants and more than 75% TOC reduction were achieved after 4 h under stoichiometric H 2 O 2 dose, 100 mg L −1 initial chlorophenol concentration, 1 g L −1 catalyst, pH 3 and 50 °C temperature. Moreover, complete dechlorination of all the Chlorophenols tested was achieved, being the residual organic by-products short-chain acids without significance in terms of ecotoxicity. The catalyst showed a remarkable stability in long-term continuous experiments with limited Fe leaching, below 5% of the initial loading after 100 h on stream. An additional clear advantage of the new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field.
-
treatment of Chlorophenols bearing wastewaters through hydrodechlorination using pd activated carbon catalysts
Carbon, 2004Co-Authors: L Calvo, Angel F. Mohedano, Jose A Casas, M A Gilarranz, Juan J. RodriguezAbstract:Abstract The catalytic hydrodechlorination of 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol in aqueous solution over Pd/activated carbon catalysts (0.5% w/w Pd) was studied in a fixed bed reactor. The reactor was fed with a 100 mg/l solution of chlorophenol and a H2/N2 (1:1) gas stream. The ranges studied for temperature, pressure and space–time were 25–100 °C, 1.8–6.0 bar and 14–55 kg h/mol, respectively. A commercial and some home-made catalysts were tested. The carbon supports were subjected to oxidation with nitric acid and sodium persulfate. Chlorophenols conversion was found to peak for pressure values ≈2.4 bar. In these conditions, an increase of reaction temperature increases conversion. In the runs carried out at high space–time both the reactants conversion and the selectivity towards end chain reaction products was enhanced. The oxidation of the carbon support with nitric acid prior to impregnation improves conversion. At the optimum conditions (2.4 bar, 75 °C and nitric acid oxidation of carbon support) conversion values over 95% were reached for all Chlorophenols. As a result of this treatment the toxicity of the initial solutions was reduced by more than 90%.
Guohua Chen - One of the best experts on this subject based on the ideXlab platform.
-
catalytic dechlorination of Chlorophenols in water by palladium iron
Water Research, 2001Co-Authors: Fenglin Yang, Guohua ChenAbstract:Abstract Three isomer Chlorophenols, o -, m -, p -chlorophenol, were dechlorinated by palladium/iron powder in water through catalytic reduction. The dechlorinated reaction is believed to take place on the surface site of the catalyst in a pseudo-first-order reaction. The reduction product for all the three isomers is phenol. The dechlorination rate increases with increase of bulk loading of palladium due to the increase of both the surface loading of palladium and the total surface area. The molecular structure also has an effect on the dechlorination rate. For conditions with 0.048% Pd/Fe, the rate constants are 0.0215, 0.0155 and 0.0112 min −1 for o -, m -, p -chlorophenol, respectively. Almost complete dechlorination is achieved within 5 h.
Manuel A Rodrigo - One of the best experts on this subject based on the ideXlab platform.
-
electrochemical oxidation of several Chlorophenols on diamond electrodes part i reaction mechanism
Journal of Applied Electrochemistry, 2003Co-Authors: Pablo Canizares, J Garciagomez, Cristina Saez, Manuel A RodrigoAbstract:The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the Chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C4 carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of Chlorophenols.