Juan F. García-Araya

Universidad de Extremadura, Ara Pacis Augustalis, Extremadura, Spain

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Publications (44)126.41 Total impact

  • O. Gimeno · J.F. García-Araya · FJ. Beltrán · F.J. Rivas · A. Espejo
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    ABSTRACT: Treatment of primary wastewater effluent containing a mixture of nine pharmaceuticals model compounds (acetaminophen ACM, antipyrine ANT, caffeine CAF, ketorolac KET, metoprolol MET, sulfamethoxazole SFX, carbamazepine CARB, hydrochlorothiazide HCT and diclofenac DIC) has been carried out by means of aerobic biodegradation followed by different advanced oxidation processes (solar heterogeneous photocatalysis with TiO2, solar photo-Fenton and ozonation). Only ACM and CAF were completely removed from municipal wastewater in aerobic biological experiments. Apparently, the bacteriostatic nature of SFX could lead tosome extent to bacterial growth inhibition. Photocatalytic ozonation allows for a higher degradation rate than simple photocatalytic oxidation in the presence of oxygen. Under the conditions investigated, emerging compounds (ECs)degradation (sum of concentrations) in the photocatalytic ozonation was in the range 80-100% depending on the system. Application of solar light (SL) Fe(III) photocatalytic ozonation, SL/O3/Fe (III) (180 min) and ozonation (45 min) systems reduced the concentrations of the studied emerging contaminants below their detection limit (2μg L-1). Nevertheless,photocatalytic ozonationled to 41.3 % mineralization compared to 34% achieved by singleozonation.Toxicity analyses by Daphnia magna showed no effluent toxicity after the application of the three tertiary treatments.
    No preview · Article · Jan 2016
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    ABSTRACT: A synthetic secondary effluent containing an aqueous mixture of emerging contaminants (ECs) has been treated by photocatalytic ozonation using Fe(3+) or Fe3O4 as catalysts and black light lamps as the radiation source. For comparative purposes, ECs have also been treated by ultraviolet radiation (UVA radiation, black light) and ozonation (pH 3 and 7). With the exception of UVA radiation, O3-based processes lead to the total removal of ECs in the mixture. The time taken to achieve complete degradation depends on the oxidation process applied. Ozonation at pH 3 is the most effective technique. The addition of iron based catalysts results in a slight inhibition of the parent compounds degradation rate. However, a positive effect is experienced when measuring the total organic carbon (TOC) and the chemical oxygen demand (COD) removals. Photocatalytic oxidation in the presence of Fe(3+) leads to 81% and 88% of TOC and COD elimination, respectively, compared to only 23% and 29% of TOC and COD removals achieved by single ozonation. The RCT concept has been used to predict the theoretical ECs profiles in the homogeneous photocatalytic oxidation process studied. Treated wastewater effluent was toxic to Daphnia magna when Fe(3+) was used in photocatalytic ozonation. In this case, toxicity was likely due to the ferryoxalate formed in the process. Single ozonation significantly reduced the toxicity of the treated wastewater.
    No preview · Article · May 2015 · Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering
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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.
    No preview · Article · Jul 2014 · Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering
  • Almudena Aguinaco · Fernando J. Beltrán · Juan F. García-Araya · Ana L. Oropesa
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    ABSTRACT: Photocatalytic ozonation (O3/UVA/TiO2) of diclofenac (DCF), a non-steroidal anti-inflammatory drug (NSAID) and emerging water pollutant, was studied through the influence of some operational variables (gas flow rate, initial concentrations of ozone, DCF and TiO2), ozone consumption and ecotoxicity. Further, the stability and activity of the catalyst was investigated. Both ozone gas and initial diclofenac concentrations highly affected DCF and total organic carbon (TOC) removals while the gas flow rate exerted a negligible influence under the experimental conditions here applied. Complete elimination of DCF was achieved within 6 min and from 60 to 75% of TOC removals were observed after 60 min of reaction regardless of the water matrix used, ultrapure water or urban waste wastewater. Optimum concentration of TiO2 was found between 0.5 and 2.5 g L−1 and ozone consumption around 6 mg per mg TOC consumed was obtained after 30 min of reaction. Daphnia magna exposition to untreated DCF aqueous solution led to 65% of death of these organisms, though after treatment, ecotoxicity levels of 20% were achieved. Photocatalytic ozonation showed the lowest ozone consumption and ecotoxicity compared to the other ozonation systems tested. Moreover, loss in the catalyst activity was not observed after 8 h of use as well as no leaching of Ti was detected.
    No preview · Article · May 2012 · The Chemical Engineering Journal
  • F.J. Beltran · Almudena Aguinaco · Ana Rey · Juan F. García-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.
    No preview · Article · Mar 2012 · Industrial & Engineering Chemistry Research
  • 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.
    No preview · Article · Jan 2012 · Ozone Science and Engineering
  • 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.
    No preview · Article · Oct 2010 · Applied Catalysis B Environmental
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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.
    No preview · Article · Jul 2010 · Ozone Science and Engineering
  • 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
    No preview · Article · Jun 2010 · Journal of Chemical Technology & Biotechnology
  • 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.
    No preview · Article · Mar 2009 · Water Research
  • Fernando J Beltrán · Almudena Aguinaco · Juan F García-Araya · Ana L. Oropesa
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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.
    No preview · Article · Sep 2008 · Water Research
  • 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.
    No preview · Article · Jul 2008 · Ozone Science and Engineering
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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.
    Full-text · Article · Jun 2008 · Journal of Hazardous Materials
  • 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.
    No preview · Article · Apr 2008 · Ozone Science and Engineering
  • 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.
    No preview · Article · Apr 2008 · Ozone Science and Engineering
  • 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.
    No preview · Article · Oct 2007 · Industrial & Engineering Chemistry Research
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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.
    No preview · Article · Nov 2006 · Carbon
  • Fernando J. Beltrán · Juan F. García-Araya · Inés Giráldez · Francisco J. Masa
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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.
    No preview · Article · Mar 2006 · Industrial & Engineering Chemistry Research
  • 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.
    No preview · Article · Mar 2006 · Applied Catalysis B Environmental
  • J.F. García-Araya · F.J. Beltrán · I. Giráldez · P. Álvarez · F. Medina · V. Navarrete

    No preview · Article · Jan 2006