Juan F. García-Araya

Universidad de Extremadura, Cáceres, Extremadura, Spain

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Publications (41)50.43 Total impact

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    ABSTRACT: Sequential treatments consisting in a chemical process followed by a conventional biological treatment, have been applied to remove mixtures of nine contaminants of pharmaceutical type spiked in a primary sedimentation effluent of a municipal wastewater. Combinations of ozone, UVA black light (BL) and Fe(III) or Fe3O4 catalysts constituted the chemical systems. Regardless of the Advanced Oxidation Process (AOP), the removal of pharmaceutical compounds was achieved in 1 h of reaction, while total organic carbon (TOC) only diminished between 3.4 and 6%. Among selected ozonation systems to be implemented before the biological treatment, the application of ozone alone in the pre-treatment stage is recommended due to the increase of the biodegradability observed. The application of ozone followed by the conventional biological treatment leads high TOC and COD removal rates, 60 and 61%, respectively, and allows the subsequent biological treatment works with shorter hydraulic residence time (HRT). Moreover, the influence of the application of AOPs before and after a conventional biological process was compared, concluding that the decision to take depends on the characterization of the initial wastewater with pharmaceutical compounds.
    Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 07/2014; 49(9):1015-22.
  • Fernando J. Beltrán, Almudena Aguinaco, Juan F. García-Araya
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    ABSTRACT: Different UVA radiation and advanced oxidation systems, most of them involving ozone, have been applied to remove mixtures of three contaminants of pharmaceutical type: diclofenac (DCF), sulfamethoxazole (SMT) and caffeine (CFF), both in ultrapure and secondary treated wastewater. The influence of the water matrix has been studied in terms of individual compound concentration and TOC removal. Also, biodegradability of the treated wastewater before and after the advanced oxidation process, as BOD/COD ratio, the partial oxidation yield, the increment of average state of carbon oxidation and ozone consumption have been determined. For mgL to 100 μgL concentrations and regardless of the ozone process and water type, DCF and SMT are removed in less than 10 min mainly by direct reaction with ozone, especially in the case of DCF. CFF, on the contrary, is mainly removed through hydroxyl radicals. For lower concentration (≤100 μgL), DCF still disappears by direct ozonation, CFF by hydroxyl radicals oxidation and SMT through both direct ozonation and hydroxyl radical oxidation. Once DCF and SMT have disappeared, TOC is removed by reacting with hydroxyl radicals, regardless of the water matrix. Photocatalytic ozonation allows the highest TOC degradation rate, partial oxidation yield, increment of average state of carbon oxidation and biodegradability together to the lowest ozone consumption per mg TOC eliminated.
    Ozone Science and Engineering 01/2012; 34(1):3-15. · 0.81 Impact Factor
  • F.J. Beltran, A. Aguinaco, A. Rey, J.F. Garcia-Araya
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    ABSTRACT: Black light photocatalytic ozonation of two pharmaceutical compounds, sulfamethoxazole (SMX) and diclofenac (DCF), and the resulting total organic carbon (TOC) are studied. DCF and SMX removals from some mg·L–1 to 100 μg·L–1 are achieved in approximately 7 and 15 min ozonation, respectively, regardless of the ozone process, while the resulting TOC is eliminated via hydroxyl radical reactions. For initial concentrations lower than 50 μg·L–1, competition between direct ozonation and hydroxyl radical oxidation to eliminate SMX and DCF takes place. The initial reaction period for cases of high and low concentration is simulated through fast-moderate and slow gas–liquid second order reaction kinetics, respectively. For high starting concentrations the calculated results suggest the presence of ozone fast reacting intermediates. For low starting concentration, calculated results indicate the importance of hydroxyl radical oxidation and the synergic effect of ozone and photocatalytic oxidation. Kinetic data of TOC ozonation, photocatalytic oxidation, and photocatalytic ozonation are also presented.
    Industrial & Engineering Chemistry Research 01/2012; 51:4533-4544. · 2.24 Impact Factor
  • Juan F. García-Araya, Fernando J. Beltrán, Almudena Aguinaco
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    ABSTRACT: BACKGROUND: The aim of this work was to establish the efficiency of single ozonation at different pH levels (5, 7 and 9) and with different TiO2 photolytic oxidizing systems (O2/UV-A/TiO2, O3/UV-A/TiO2 or UV-A/TiO2) for diclofenac removal from water, with especial emphasis on mineralization of the organic matter.RESULTS: In the case of single ozonation processes, results show fast and practically complete elimination of diclofenac, with little differences in removal rates that depend on pH and buffering conditions. In contrast, total organic carbon (TOC) removal rates are slow and mineralization degree reaches 50% at best. As far as photocatalytic processes are concerned, diclofenac is completely removed from the aqueous solutions at high rates. However, unlike single ozonation processes, TOC removal can reach 80%.CONCLUSION: In single ozonation processes, direct ozone reaction is mainly responsible for diclofenac elimination. Once diclofenac has disappeared, its by-products are removed by reaction with hydroxyl radicals formed in the ozone decomposition and also from the reaction of diclofenac with ozone. In the photocatalytic processes hydroxyl radicals are responsible oxidant species of diclofenac removal as well as by-products. Copyright © 2010 Society of Chemical Industry
    Journal of Chemical Technology & Biotechnology 03/2010; 85(6):798 - 804. · 2.50 Impact Factor
  • Fernando J. Beltrán, Almudena Aguinaco, Juan F. García-Araya
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    ABSTRACT: A kinetic model for aqueous diclofenac photocatalytic ozonation is proposed and experimentally tested. The kinetic model, based on mol balance equations of main species present in water, gives total organic carbon (TOC), ozone and hydrogen peroxide concentrations with time as output variables. The model relies on both, experimental data obtained in this work (i.e. rate constant of reactions and quantum yield values) and published data on the nature of intermediate formation, free radicals and hydrogen peroxide yield and rate constants of the reactions between intermediates, ozone and hydroxyl radicals. Intermediates of different structure and reactivity towards ozone and hydroxyl radical have been classified into groups. Accordingly, the remaining TOC in water, at each time, is considered as the sum of the contributing TOC values of these groups. The kinetic model is applied to buffered systems and acceptably reproduces the experimental results for the reaction period investigated.
    Applied Catalysis B-environmental - APPL CATAL B-ENVIRON. 01/2010; 100(1):289-298.
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    ABSTRACT: The ozonation of two pharmaceutical compounds: the drug diclofenac (DCF) and the synthetic hormone 17α-ethynylstradiol (EST), has been studied in laboratory prepared water and domestic wastewater in the presence of perovskite catalysts. In ultrapure water, catalysts do not lead to any improvement on the ozonation rates of DCF and EST which supports the fact that both compounds are removed by direct ozonation. TOC removal, on the other hand, is significantly increased in the presence of perovskite catalysts, especially when copper perovskite is used, with TOC removals in the order of 90% after 120 minutes of reaction. In domestic wastewater the results are similar regarding the mechanism of initial pharmaceutical compounds removal, which are due to direct reactions with ozone that, in this case, develop during longer reaction times likely due to the presence of other contaminants. Then, regarding TOC removal in domestic wastewater, negligible differences between non-catalytic and catalytic ozonation are observed during the first approximately 25 minutes of reaction. For higher reaction time, TOC removal is improved only in the case copper perovskite catalyst is used although percentages of TOC removal are comparatively lower than those reached in ultrapure water (they hardly reach 50% TOC removal). Finally, a kinetic study has been carried out and apparent rate constants of the heterogeneous reaction between ozone and TOC on the catalyst surface have been determined.
    Ozone-science & Engineering - OZONE-SCI ENG. 01/2010; 32(4):230-237.
  • Fernando J Beltrán, Almudena Aguinaco, Juan F García-Araya
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    ABSTRACT: The photocatalytic ozonation of sulfamethoxazole (SMT) has been studied in water under different experimental conditions. The effect of gas flow rate, initial concentration of ozone, SMT and TiO2 has been investigated to establish the importance of mass transfer and chemical reaction. Under the conditions investigated the process is chemically controlled. Both, SMT and TOC kinetics have been considered. Fast and slow kinetic regime of ozone reactions have been observed for SMT and TOC oxidation, respectively. Application of different inhibitors allows for the establishment of reaction mechanism involving direct ozonation, direct photolysis, hydroxyl radical reactions and photocatalytic reactions. Rate constants of the direct reaction between ozone and protonated, non-protonated and anionic SMT species have been determined to be 1.71 x 10(5), 3.24 x 10(5) and 4.18 x 10(5) M(-1) s(-1), respectively. SMT quantum yield at 313 nm was found to be 0.012 moles per Einstein at pH 5 and 0.003 moles per Einstein at pHs 7 and 9. Main contributions to SMT removal were direct ozone reaction, positive hole oxidation and hydroxyl radical reactions. For TOC removal, main contributions were due to positive hole oxidation and hydroxyl radical reactions.
    Water Research 01/2009; 43(5):1359-69. · 4.66 Impact Factor
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    ABSTRACT: In this study, water containing the pharmaceutical compound sulfamethoxazole (SMT) was subjected to the various treatments of different oxidation processes involving ozonation, and photolysis and catalysis under different experimental conditions. Removal rates of SMT and total organic carbon (TOC), from experiments of simple UVA radiation, ozonation (O(3)), catalytic ozonation (O(3)/TiO(2)), ozone photolysis (O(3)/UVA), photocatalytic oxidation (O(2)/TiO(2)/UVA) and photocatalytic ozonation (O(3)/UVA/TiO(2)), have been compared. Photocatalytic ozonation leads to the highest SMT removal rate (pH 7 in buffered systems, complete removal is achieved in less than 5min) and total organic carbon (in unbuffered systems, with initial pH=4, 93% TOC removal is reached). Also, lowest ozone consumption per TOC removed and toxicity was achieved with the O(3)/UVA/TiO(2) process. Direct ozone and free radical reactions were found to be the principal mechanisms for SMT and TOC removal, respectively. In photocatalytic ozonation, with buffered (pH 7) aqueous solutions phosphates (buffering salts) and accumulation of bicarbonate scavengers inhibit the reactions completely on the TiO(2) surface. As a consequence, TOC removal diminishes. In all cases, hydrogen peroxide plays a key role in TOC mineralization. According to the results obtained in this work the use of photocatalytic ozonation is recommended to achieve a high mineralization degree of water containing SMT type compounds.
    Water Research 09/2008; 42(14):3799-808. · 4.66 Impact Factor
  • F.J. Beltrán, J.M. Encinar, J.F. García-Araya, M.A. Alonso
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    ABSTRACT: Kinetic studies of the ozonation of two wastewaters released by distillery and tomato processing plants have been carried out. Once it has been assumed that an irreversible gas-liquid reaction is developed between ozone and the matter present in the water, the film theory concept was applied to this system for kinetic determinations. The evolution of the organic and inorganic matter with ozonation time has been followed by the chemical oxygen demand. The procedure allows the determination of the rate coefficients of ozone with the wastewaters treated. According to the results obtained, ozone is consumed through fast reactions which take place near the water-gas interface during an initial period. This period is used to determine the rate coefficients. Then, at more advanced ozonation times, the reactions become slower and hence they take place in the bulk of the water, articularly for the case of tomato wastewaters. Values of the rate coefficient allow us to establish both the kinetic regime of absorption and to compare the reactivity of ozone with the wastewaters and single compounds.
    Ozone Science and Engineering 07/2008; No. 4(August 1992):303-327. · 0.81 Impact Factor
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    F Javier Rivas, Ruth García, Juan F García-Araya, Olga Gimeno
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    ABSTRACT: The treatment of an aqueous solution of four polycyclic aromatic hydrocarbons, namely acenaphthene, phenanthrene, anthracene and fluoranthene, under moderate conditions of temperature and pressure has been conducted in the presence and absence of free radical promoters (hydrogen peroxide or potassium monopersulfate). With no addition of promoters, the process achieves PAH conversion values in the range 80-100% at 190 degrees C and 50 bars of air pressure (80 min of reaction). Similar results are obtained in the presence of hydrogen peroxide, however, in this case, the time required is just 60 min with a sharp decrease in PAH concentration in the first 10-20 min. Additionally, temperature can be lowered to values in the range 100-150 degrees C. If potassium monopersulfate is used instead of hydrogen peroxide, an analogous behaviour is experienced, in the latter case, temperatures above 120 degrees C lead to an inhibition of anthracene oxidation, likely due to ineffective decomposition of the monopersulfate molecule.
    Journal of Hazardous Materials 06/2008; 153(1-2):792-8. · 3.93 Impact Factor
  • F.J. Beltrán, J.F. García-Araya, J.M. Encinar
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    ABSTRACT: A procedure for the determination of Henry and mass transfer coefficients in an ozone-industrial wastewater system is presented. The method is applied to the ozonation of a tomato plant industrial wastewater, developed in the slow kinetic regime. In so doing, molar balances of ozone (in gas and water phases) are used together with gas-liquid reaction kinetic theory. While Henry's coefficients obtained are similar to those corresponding to ozonation in organic-free water, significant deviations are observed regarding the mass transfer coefficient.
    Ozone-science & Engineering - OZONE-SCI ENG. 04/2008; 19(3):281-296.
  • F.J. Beltrán, J.M. Encinar, J.F. García-Araya
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    ABSTRACT: A kinetic model constituted by ozone mol balance equations both in the gas and in the water phases and a total mole balance equation has been applied to predict concentrations of dissolved ozone, Co3, ozone partial pressure at the reactor outlet, P(o3)0, and remaining chemical oxygen demand, COD, for the ozonation of two industrial wastewaters released from distillery and tomato processing plants.Kinetic equations for ozone absorption rate present in the model were derived from the application of film theory to an irreversible gas-liquid reaction. Parameters involved in the model, reaction rate and mass transfer coefficients, Henry's law constant, etc., were estimated from bench-scale experiments. The model was applied to ozonation in bubble contactors of height/diameter ratio equal to that of the bench scale contactor and to a pilot plant bubble column of a height/diameter ratio about 3.6 times higher.
    Ozone-science & Engineering - OZONE-SCI ENG. 04/2008; 17(4):379-398.
  • Inés Giráldez, Juan F. García-Araya, Fernando J. Beltrán
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    ABSTRACT: A mixture of polyphenol compounds (gallic acid, tyrosol, and syringic acid) is treated with ozone in water in the presence of activated carbon (AC). Individual (O3) and combined (O3/AC) ozonations have been carried out following the concentrations of initial compounds, intermediates, ozone, and hydrogen peroxide and total organic carbon (TOC). AC ozonation processes significantly improve both polyphenol conversion and mineralization. Hydrogen peroxide formed during the process seems to play an important role in accelerating the oxidation rate. Different carboxylic acids are formed as intermediate products. Consumption of ozone per unit mass of carbon removed is reduced in the combined ozonation process.
    Industrial & Engineering Chemistry Research - IND ENG CHEM RES. 10/2007; 46(24).
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    ABSTRACT: The ozonation of succinic acid in water has been carried out in the presence of four different activated carbons. The influence of some variables, carbon type, particle size, gas flow rate, agitation speed, etc., has been studied for kinetic purposes. Succinic acid has been observed to be a promoter of ozone decomposition in water. Reactivity of ozone with succinic acid is significantly increased in the presence of activated carbon, regardless of its nature, although basic activated carbons present the highest activity. Also, the presence of activated carbon allows the highest mineralization rates. Mass transfer and chemical reactions (bulk water and surface reactions) have been considered for the kinetic study and rate constants of both reactions have been determined at different temperatures. Linear correlations have been obtained between surface reaction rate constants and the pHpzc of activated carbons.
    Industrial & Engineering Chemistry Research - IND ENG CHEM RES. 03/2006; 45(9).
  • Fernando J. Beltrán, Juan F. García-Araya, Inés Giráldez
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    ABSTRACT: The ozonation of gallic acid in water in the presence of activated carbon has been studied at pH 5. Hydrogen peroxide, ketomalonic and oxalic acids were identified as by-products. The process involves two main periods of reaction. The first period, up to complete disappearance of gallic acid, during which ozonation rates are slightly improved by the presence of activated carbon. The second one, during which activated carbon plays an important role as promoter, and total mineralization of the organic content of the water is achieved. The organic matter removal is due to the sum of contributions of ozone direct reactions and adsorption during the first period and to a free radical mechanism likely involving surface reactions of ozone and hydrogen peroxide on the carbon surface during the second period. There is a third transition period where by-products concentration reach maximum values and ozonation is likely due to both direct and free radical mechanisms involving ozone and adsorption. Discussion on the mechanism and kinetics of the process is also presented both for single ozonation and activated carbon ozonation.
    Applied Catalysis B: Environmental. 01/2006; 63:249-259.
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    ABSTRACT: The decomposition of aqueous ozone in the presence of various granular activated carbons (GAC) was studied. The variables investigated were GAC dose, presence of tert-butyl alcohol (TBA), aqueous pH as well as textural and chemistry surface properties of GAC. All the GAC tested enhanced the rate of ozone decomposition to some extent. From the analysis of experimental results it was deduced that ozone transformation into HO radicals mainly occurred in the liquid bulk through a radical chain reaction initiated by OH− and ions. Hydroperoxide ions arise from the formation of H2O2 on surface active sites of GAC and its further dissociation. No direct relationship between textural properties of GAC and the rate of ozone decomposition was found. However, a multiple regression analysis of data revealed that basic and hydroxyl surface oxygen groups (SOG) of GAC favor the kinetics of the ozone decomposition process. It is thought that these groups are the active sites for ozone transformation into H2O2. Repeated used of GAC in ozonation experiments resulted in loss of basic and hydroxyl SOG with formation of carboxyl, carbonyl and lactone-type groups. Then, pre-ozonation of GAC reduces its ability to enhance the aqueous ozone transformation into hydroxyl radicals.
    Carbon. 01/2006;
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    P M Alvarez, J F García-Araya, F J Beltrán, F J Masa, F Medina
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    ABSTRACT: The impact of ozonation on textural and chemical surface characteristics of two granular activated carbons (GAC), namely F400 and AQ40, and their ability to adsorb phenol (P), p-nitrophenol (PNP), and p-chlorophenol (PCP) from aqueous solutions have been studied. The porous structure of the ozone-treated carbons remained practically unchanged with regard to the virgin GAC. However, important modifications of the chemical surface and hydrophobicity were observed from FTIR spectroscopy, pH titrations, and determination of pH(PZC). As a rule, the ozone treatment at either room temperature (i.e., about 25 degrees C) or 100 degrees C gave rise to acidic surface oxygen groups (SOG). At 25 degrees C primarily carboxylic acids were formed while a more homogeneous distribution of carboxylic, lactonic, hydroxyl, and carbonyl groups was obtained at 100 degrees C. The experimental isotherms for phenolic compounds on both GAC were analyzed using the Langmuir model. Dispersive interactions between pi electrons of the ring of the aromatics and those of the carbon basal planes were thought to be the primary forces responsible for the physical adsorption whereas oxidative coupling of phenolic compounds catalyzed by basic SOG was a major cause of irreversible adsorption. The exposure of both GAC to ozone at room temperature decreased their ability to adsorb P, PNP, and PCP. However, when ozone was applied at 100 degrees C adsorption was not prevented but in some cases (P and PNP on F400) the adsorption process was even enhanced.
    Journal of Colloid and Interface Science 04/2005; 283(2):503-12. · 3.17 Impact Factor
  • J.F. García-Araya, F.J. Beltrán, P. Álvarez, F.J. Masa
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    ABSTRACT: Single solute and simultaneous experimental adsorption isotherms of three phenolic compounds: gallic acid, p-hydroxybenzoic acid and syringic acid, have been investigated at 20, 30 and 40C, using a bituminous coal based activated carbon. Regardless of temperature, the capacity of the activated carbon used to adsorb these compounds presented the following order: syringic acid > p-hydroxybenzoic acid > gallic acid. The increase of temperature slightly favored the adsorption capacity of the phenolic compounds. In binary and ternary component adsorption, experimental data suggest that interactions between adsorbates improve the adsorption capacity of some of the phenolic acid compounds. On the contrary, at high organic concentrations, adsorbed gallic acid was partially removed from the activated carbon surface because of the presence of the other components.
    Adsorption 05/2003; 9(2):107-115. · 1.55 Impact Factor
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    ABSTRACT: The system Fe(III)/H2O2 has been used to oxidise an aqueous solution of p-hydroxybenzoic acid (pHB) in the absence of light. In the process, typical operating variables such as reagent concentration exert a positive influence in the pHB degradation rate. Optimum pH has been found to be around 3. The kinetic study suggests that the mechanism involved in this system differs to some extent from that reported for the classic Fenton's chemistry in pure water. Thus, formation of a complex Fe(III)-pHB seems to be a key step to initiate the oxidising mechanism. Stoichiometric measurements of the H2O2 consumption per mole of pHB degraded indicate a possible reduction of complexed Fe(III). Simultaneous oxidation of pHB (and other similar compounds such as tyrosol (Ty) or p-coumaric acid (pCu)) and atrazine have shown a synergistic effect of the first substance to remove the pesticide.
    Journal of Hazardous Materials 05/2002; 91(1-3):143-57. · 3.93 Impact Factor
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    ABSTRACT: Direct photolysis with UV radiation (254 nm) and oxidation with ozone combined with UV radiation of three polynuclear aromatic hydrocarbons, fluorene, phenanthrene, and acenaphthene, has been studied. Quantum yields of the direct photolysis of the PAHs determined were 7.5 {times} 10{sup {minus}3}, 6.9 {times} 10{sup {minus}3}, and 52 {times} 10{sup {minus}3} mol(photon){sup {minus}1} for fluorene, phenanthrene, and acenaphthene, respectively. Contributions of direct ozonation, direct photolysis, and radical oxidation have also been estimated for the oxidation with ozone combined with UV radiation. Fluorene is oxidized by direct photolysis and radical reactions, phenanthrene through direct mechanisms, ozonation, and photolysis, and acenaphthene mainly by direct ozonation.
    Industrial & Engineering Chemistry Research 04/2002; 34(5). · 2.24 Impact Factor