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Escuela de Ingeniería de Vitoria-Gasteiz. Department of Environmental and Chemical Engineering. University of the Basque Country UPV/EHU
This work studied the removal of phenol from industrial effluents through catalytic ozonation in the presence of granular activated carbon in a continuous fixed-bed reactor. Phenol was chosen as model pollutant because of its environmental impact and high toxicity. Based on the evolution of total organic carbon (TOC) and phenol concentration, a kinetic model was proposed to study the effect of the operational variables on the combined adsorption–oxidation (Ad/Ox) process. The proposed three-phase model expressed the oxidation phenomena in the liquid and the adsorption and oxidation on the surface of the granular activated carbon in the form of two kinetic constants, k1 and k2 respectively. The interpretation of the constants allow to study the benefits and behaviour of the use of activated carbon during the ozonisation process under different conditions affecting adsorption, oxidation, and mass transfer. Additionally, the calculated kinetic parameters helped to explain the observed changes in treatment efficiency. The results showed that phenol would be completely removed at an effective contact time of 3.71 min, operating at an alkaline pH of 11.0 and an ozone gas concentration of 19.0 mg L−1. Under these conditions, a 97.0% decrease in the initial total organic carbon was observed.
Cristian Ferreiro; Ana de Luis; Natalia Villota; Jose María Lomas; José Ignacio Lombraña; Luis Miguel Camarero. Application of a Combined Adsorption−Ozonation Process for Phenolic Wastewater Treatment in a Continuous Fixed-Bed Reactor. Catalysts 2021, 11, 1014 .
AMA StyleCristian Ferreiro, Ana de Luis, Natalia Villota, Jose María Lomas, José Ignacio Lombraña, Luis Miguel Camarero. Application of a Combined Adsorption−Ozonation Process for Phenolic Wastewater Treatment in a Continuous Fixed-Bed Reactor. Catalysts. 2021; 11 (8):1014.
Chicago/Turabian StyleCristian Ferreiro; Ana de Luis; Natalia Villota; Jose María Lomas; José Ignacio Lombraña; Luis Miguel Camarero. 2021. "Application of a Combined Adsorption−Ozonation Process for Phenolic Wastewater Treatment in a Continuous Fixed-Bed Reactor." Catalysts 11, no. 8: 1014.
The objective of this study is to evaluate the turbidity generated during the Fenton photo-reaction applied to the oxidation of waters containing carbamazepine as a function of factors such as pH, H2O2 concentration and catalyst dosage. The results let establish the degradation pathways and the main decomposition byproducts. It is found that the pH affects the turbidity of the water. Working between pH = 2.0 and 2.5, the turbidity is under 1 NTU due to the fact that iron, added as a catalyst, is in the form of a ferrous ion. Operating at pH values above 3.0, the iron species in their oxidized state (mainly ferric hydroxide in suspension) would cause turbidity. The contribution of these ferric species is a function of the concentration of iron added to the process, verifying that the turbidity increases linearly according to a ratio of 0.616 NTU L/mg Fe. Performing with oxidant concentrations at (H2O2) = 2.0 mM, the turbidity undergoes a strong increase until reaching values around 98 NTU in the steady state. High turbidity levels can be originated by the formation of coordination complexes, consisting of the union of three molecules containing substituted carboxylic groups (BaQD), which act as ligands towards an iron atom with Fe3+ oxidation state.
Natalia Villota; Cristian Ferreiro; Hussein Qulatein; Jose Lomas; Jose Lombraña. Turbidity Changes during Carbamazepine Oxidation by Photo-Fenton. Catalysts 2021, 11, 894 .
AMA StyleNatalia Villota, Cristian Ferreiro, Hussein Qulatein, Jose Lomas, Jose Lombraña. Turbidity Changes during Carbamazepine Oxidation by Photo-Fenton. Catalysts. 2021; 11 (8):894.
Chicago/Turabian StyleNatalia Villota; Cristian Ferreiro; Hussein Qulatein; Jose Lomas; Jose Lombraña. 2021. "Turbidity Changes during Carbamazepine Oxidation by Photo-Fenton." Catalysts 11, no. 8: 894.
The oxidation of aqueous solutions of carbamazepine is conducted using the Fenton reagent, combined with the photolytic action of a 150 W medium pressure UV lamp, operating at T = 40 °C. The effect of acidity is analysed at an interval pH = 2.0–5.0, verifying that operating at pH = 5.0 promotes colour formation (Colour = 0.15 AU). The effect of iron is studied, finding that the colour of the water increases in a linear way, Colour = 0.05 + 0.0075 [Fe]0. The oxidising action of hydrogen peroxide is tested, confirming that when operating with [H2O2]0 = 2.0 mM, the maximum colour is generated (Colourmax = 0.381 AU). The tint would be generated by the degradation of by-products of carbamazepine, which have chromophoric groups in their internal structure, such as oxo and dioxocarbazepines, which would produce tint along the first minutes of oxidation, while the formation of acridones would slowly induce colour in the water.
Natalia Villota; Cristian Ferreiro; Hussein Qulatein; Jose Lomas; Luis Camarero; José Lombraña. Colour Changes during the Carbamazepine Oxidation by Photo-Fenton. Catalysts 2021, 11, 386 .
AMA StyleNatalia Villota, Cristian Ferreiro, Hussein Qulatein, Jose Lomas, Luis Camarero, José Lombraña. Colour Changes during the Carbamazepine Oxidation by Photo-Fenton. Catalysts. 2021; 11 (3):386.
Chicago/Turabian StyleNatalia Villota; Cristian Ferreiro; Hussein Qulatein; Jose Lomas; Luis Camarero; José Lombraña. 2021. "Colour Changes during the Carbamazepine Oxidation by Photo-Fenton." Catalysts 11, no. 3: 386.
The water–development nexus is essential for the advancement and progress of cities in the face of problems such as climate change, water security and increasing environmental stress in the agricultural sector. Aiming for a circular economy and, at the same time, improving the resilience of water supply alternatives and achieving a goal of zero waste, this work presents a technical–economic study of a novel continuous ultrafiltration (c-UF) system with self-cleaning capacity coupled to an ozonation process, for the treatment of urban WWTP effluent. The removal efficiencies achieved were analysed both through macroscopic parameters (suspended solids, turbidity) and for the most frequently occurring contaminants of emerging concern (CECs). Consequently, an effluent suitable for irrigation was obtained, with a total recovery factor of 97.92%, a concentration of suspended solids (SS) below 1 mg L−1, 0.06 NTU turbidity and toxicity free, complying with the new European Regulation on Water Reuse (EU 2020/741). A comparative analysis of the proposed process with regard to conventional tertiary treatment revealed that the proposed process was 39.1% more economic, with a cost of 0.0325 € m−3. This alternative treatment will be of great interest because of its favourable technical–economic characteristics, being postulated as a basic process for implementation in modern water reuse plants.
Cristian Ferreiro; Natalia Villota; Ana de Luis; José Lombraña; Nestor Etxebarria; Jose Lomas. Water Reuse Study from Urban WWTPs via c-Ultrafiltration and Ozonation Technologies: Basis for Resilient Cities and Agriculture. Agronomy 2021, 11, 322 .
AMA StyleCristian Ferreiro, Natalia Villota, Ana de Luis, José Lombraña, Nestor Etxebarria, Jose Lomas. Water Reuse Study from Urban WWTPs via c-Ultrafiltration and Ozonation Technologies: Basis for Resilient Cities and Agriculture. Agronomy. 2021; 11 (2):322.
Chicago/Turabian StyleCristian Ferreiro; Natalia Villota; Ana de Luis; José Lombraña; Nestor Etxebarria; Jose Lomas. 2021. "Water Reuse Study from Urban WWTPs via c-Ultrafiltration and Ozonation Technologies: Basis for Resilient Cities and Agriculture." Agronomy 11, no. 2: 322.
This work aims to study the sustainable catalytic ozonation of aniline promoted by granular active carbon (GAC) doped with TiO2. Aniline was selected as a model compound for the accelerator manufacturing industries used in the manufacture of rubber due to its environmental impact, low biodegradability, and harmful genotoxic effects on human health. Based on the evolution of total organic carbon (TOC), aniline concentration measured using high performance liquid chromatography (HPLC), pH and ozone concentration in liquid and gas phase, and catalyst loading, a three-phase reaction system has been modelled. The proposed three-phase model related the ozone transfer parameters and the pseudo-first order kinetic constants through three coefficients that involve the adsorption process, oxidation in the liquid, and the solid catalyst. The interpretation of the kinetic constants of the process allowed the predominance of the mechanism of Langmuir–Hinshelwood or modified Eley–Rideal to be elucidated. Seven intermediate aromatic reaction products, representative of the direct action of ozone and the radical pathway, were identified and quantified, as well as precursors of the appearance of turbidity, with which two possible routes of degradation of aniline being proposed.
Cristian Ferreiro; Natalia Villota; José Ignacio Lombraña; María J. Rivero. Heterogeneous Catalytic Ozonation of Aniline-Contaminated Waters: A Three-Phase Modelling Approach Using TiO2/GAC. Water 2020, 12, 3448 .
AMA StyleCristian Ferreiro, Natalia Villota, José Ignacio Lombraña, María J. Rivero. Heterogeneous Catalytic Ozonation of Aniline-Contaminated Waters: A Three-Phase Modelling Approach Using TiO2/GAC. Water. 2020; 12 (12):3448.
Chicago/Turabian StyleCristian Ferreiro; Natalia Villota; José Ignacio Lombraña; María J. Rivero. 2020. "Heterogeneous Catalytic Ozonation of Aniline-Contaminated Waters: A Three-Phase Modelling Approach Using TiO2/GAC." Water 12, no. 12: 3448.
This work presents a case study of a wastewater treatment plant (WWTP), located in Biscay (Spain), in which the removal of high-occurrence contaminants of emerging concern (CEC) was studied. The existing biological treatment in the WWTP was complemented with a continuous ultrafiltration (c-UF) pilot plant, as a tertiary treatment. Thus, the effect on CEC removal of both treatments could be analyzed globally and after each operation. A total of 39 CEC were monitored, including pharmaceutical products, industrial additives, food additives, herbicides and personal care products. For evaluation of the efficiencies, the removal rates of the biological and of the c-UF treatments, including their variability over a day and a week in relation to the ammonium content, were examined in the influent of the WWTP. In the biological treatment, a wide range of different removal rates was obtained due to the different CEC’s biodegradability and concentration. In UF, lower, but more constant removal rates, were achieved. In addition, the reduction of the general toxicity by the UF treatment in terms of the Microtox® toxicity assay was also evaluated. After UF, all of the samples yielded values of TU50 lower than 1, confirming this result the UF effectiveness for toxicity removal.
Cristian Ferreiro; Iker Gómez-Motos; José Ignacio Lombraña; Ana De Luis; Natalia Villota; Oihana Ros; Nestor Etxebarria. Contaminants of Emerging Concern Removal in an Effluent of Wastewater Treatment Plant under Biological and Continuous Mode Ultrafiltration Treatment. Sustainability 2020, 12, 725 .
AMA StyleCristian Ferreiro, Iker Gómez-Motos, José Ignacio Lombraña, Ana De Luis, Natalia Villota, Oihana Ros, Nestor Etxebarria. Contaminants of Emerging Concern Removal in an Effluent of Wastewater Treatment Plant under Biological and Continuous Mode Ultrafiltration Treatment. Sustainability. 2020; 12 (2):725.
Chicago/Turabian StyleCristian Ferreiro; Iker Gómez-Motos; José Ignacio Lombraña; Ana De Luis; Natalia Villota; Oihana Ros; Nestor Etxebarria. 2020. "Contaminants of Emerging Concern Removal in an Effluent of Wastewater Treatment Plant under Biological and Continuous Mode Ultrafiltration Treatment." Sustainability 12, no. 2: 725.
Formation of oxygen in the caffeine aqueous solutions occurs through self-decomposition reactions of the hydrogen peroxide, used as an oxidant in the photo-Fenton treatment. The total concentration of hydrogen peroxide used in the treatment would be the contribution of the stoichiometric concentration that reacts with the organic matter ([H2O2]0 = 2.0 mM) and the excess of oxidant that decomposes to oxygen, through radical mechanisms, according to a ratio of 0.8164 mmol H2O2 mg-1 O2. When operating at concentrations lower than [H2O2]0 = 2.0 mM, oxygen is not released because there is no excess of oxidant. Moreover, it is verified that the ferrous ion catalyst is oxidized to ferric ion and its subsequent regeneration to ferrous ion. Working at concentrations higher than [H2O2]0 = 2.0 mM, oxygen is released in the water, verifying that the catalyst remains as ferric species, which does not regenerate. The reaction time in which oxygen evolution happpens depends on the concentration of catalyst used in the oxidation, verifying that the highest oxygen generation rates are obtained when applying [Fe]0 = 10.0 mg L-1. Once generated in the water, the maximum concentration of oxygen begins to decrease as the hydrogen peroxide is consumed, until reaching a constant value. The stages of formation and decrease of oxygen are adjusted to zero-order kinetics, estimating the kinetics constants as a function of the catalyst concentration: kf = 29.48 [Fe]0-1.25 (mg O2 L-1 min-1) and kd = -0.006 [Fe]0 2.0 + 0.244 [Fe]0-3.69 (mg O2 L-1 min-1).
Natalia Villota; Irene Coralli; Jose Lomas. Changes of dissolved oxygen in aqueous solutions of caffeine oxidized by photo-Fenton reagent. Environmental Technology 2019, 42, 609 -617.
AMA StyleNatalia Villota, Irene Coralli, Jose Lomas. Changes of dissolved oxygen in aqueous solutions of caffeine oxidized by photo-Fenton reagent. Environmental Technology. 2019; 42 (4):609-617.
Chicago/Turabian StyleNatalia Villota; Irene Coralli; Jose Lomas. 2019. "Changes of dissolved oxygen in aqueous solutions of caffeine oxidized by photo-Fenton reagent." Environmental Technology 42, no. 4: 609-617.
This work presents an efficient catalytic ozonation process for the treatment of aniline wastewater as a model pollutant. The process uses a granular activated carbon-supported titanium dioxide catalyst with environmentally-friendly and sustainable characteristics. Titanium dioxide composites were prepared by precipitation of alcoholic titanium tetrachloride solutions on two different carbon supports: Norit® GAC 1240 Plus and Norit® ROX 0.8. This method is an improvement on other composite preparation methods such as hydrothermal and impregnation by immersion techniques, which were also carried out for comparison. It characterised our composites by Brunauer–Emmett–Teller analysis, scanning electron microscopy-energy dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy to assess the influence of the carbon support. Composites synthesised via this novel precipitation method presented a 25% increase in their initial specific surface area and a 9.1% increase in titanium dioxide loading. It compared the catalytic activity of the different titanium dioxide composites on different aniline solutions, and studied the optimal pH and ozone dose. Norit® GAC 1240 Plus-supported titanium dioxide composite prepared by the precipitation method gave the highest removal yield with 80.24% mineralisation of total organic carbon in 45 min. With respect to the costs associated with the treatment, the composite achieved a removal yield of 26.8 mg ozone/mg total organic carbon.
C. Ferreiro; N. Villota; J.I. Lombraña; María J. Rivero. An efficient catalytic process for the treatment of genotoxic aniline wastewater using a new granular activated carbon-supported titanium dioxide composite. Journal of Cleaner Production 2019, 228, 1282 -1295.
AMA StyleC. Ferreiro, N. Villota, J.I. Lombraña, María J. Rivero. An efficient catalytic process for the treatment of genotoxic aniline wastewater using a new granular activated carbon-supported titanium dioxide composite. Journal of Cleaner Production. 2019; 228 ():1282-1295.
Chicago/Turabian StyleC. Ferreiro; N. Villota; J.I. Lombraña; María J. Rivero. 2019. "An efficient catalytic process for the treatment of genotoxic aniline wastewater using a new granular activated carbon-supported titanium dioxide composite." Journal of Cleaner Production 228, no. : 1282-1295.
In this work, a study of the main operating variables affecting TiO2/UV photocatalysis was carried out. The treatment of an industrial effluent containing aniline and benzothiazole from the manufacture of accelerants for vulcanization was performed in a TiO2-supported commercial photoreactor. The degradation of both contaminants was monitored by GC-MS analysis. The proposed experiments were able to properly identify the phenomenon of adsorption, as well as to improve the performance of the commercial photoreactor by adding small amounts of TiO2 in suspension. The removal performance, durability of the photocatalytic material, and energy costs were analysed. The results showed that the use of suspensions intensifies the degradation obtaining an improvement of 23.15% with respect to the use of the supported catalyst. For an aniline and benzothiazole solution, the best operating conditions were found at pH = 12.0, introducing 60.0 mg L−1 of suspended TiO2 together with the existing supported catalyst.
Cristian Ferreiro; Natalia Villota; José Ignacio Lombraña; María J. Rivero; Verónica Zúñiga; José Miguel Rituerto. Analysis of a Hybrid Suspended-Supported Photocatalytic Reactor for the Treatment of Wastewater Containing Benzothiazole and Aniline. Water 2019, 11, 337 .
AMA StyleCristian Ferreiro, Natalia Villota, José Ignacio Lombraña, María J. Rivero, Verónica Zúñiga, José Miguel Rituerto. Analysis of a Hybrid Suspended-Supported Photocatalytic Reactor for the Treatment of Wastewater Containing Benzothiazole and Aniline. Water. 2019; 11 (2):337.
Chicago/Turabian StyleCristian Ferreiro; Natalia Villota; José Ignacio Lombraña; María J. Rivero; Verónica Zúñiga; José Miguel Rituerto. 2019. "Analysis of a Hybrid Suspended-Supported Photocatalytic Reactor for the Treatment of Wastewater Containing Benzothiazole and Aniline." Water 11, no. 2: 337.
Paracetamol aqueous solutions, when ozonized, acquired a strong red coloration depending on the applied ozone dose and the initial pH of the aqueous solution. Then, this color loses intensity and turns to yellow. Color formation is favored when operating at initial pH0 = 12.0 and ozone flow-rate 4.2 mg/min. A mechanism describing color formation was proposed, being the main pathway involved an initial paracetamol hydroxylation to yield 3-hydroxyacetaminophen followed by the formation of 2-amino-5-hydroxyacetofenone. Then, these compounds are degraded to colored oxidation by-products. A model describing color evolution was also proposed, considering first-order kinetics for both color formation and degradation. The corresponding kinetic constant values were determined to be kf = 0.01 (1/min) and kd = 0.03 pH −0.055 (1/min), respectively. A relationship between aromaticity loss and color changes during the reaction has been estimated considering the parameter α=kA/kf, being α = 1.62 pH + 3.5 and the first-order rate constant for aromaticity loss given by kA = 0.0162 pH + 0.035 (1/min).
Natalia Villota; J.I. Lombraña; A. Cruz-Alcalde; M. Marcé; S. Esplugas. Kinetic study of colored species formation during paracetamol removal from water in a semicontinuous ozonation contactor. Science of The Total Environment 2018, 649, 1434 -1442.
AMA StyleNatalia Villota, J.I. Lombraña, A. Cruz-Alcalde, M. Marcé, S. Esplugas. Kinetic study of colored species formation during paracetamol removal from water in a semicontinuous ozonation contactor. Science of The Total Environment. 2018; 649 ():1434-1442.
Chicago/Turabian StyleNatalia Villota; J.I. Lombraña; A. Cruz-Alcalde; M. Marcé; S. Esplugas. 2018. "Kinetic study of colored species formation during paracetamol removal from water in a semicontinuous ozonation contactor." Science of The Total Environment 649, no. : 1434-1442.
Natalia Villota; Jose Lomas; Luis Miguel Camarero. Kinetic modelling of water-color changes in a photo-Fenton system applied to oxidate paracetamol. Journal of Photochemistry and Photobiology A: Chemistry 2018, 356, 573 -579.
AMA StyleNatalia Villota, Jose Lomas, Luis Miguel Camarero. Kinetic modelling of water-color changes in a photo-Fenton system applied to oxidate paracetamol. Journal of Photochemistry and Photobiology A: Chemistry. 2018; 356 ():573-579.
Chicago/Turabian StyleNatalia Villota; Jose Lomas; Luis Miguel Camarero. 2018. "Kinetic modelling of water-color changes in a photo-Fenton system applied to oxidate paracetamol." Journal of Photochemistry and Photobiology A: Chemistry 356, no. : 573-579.
Natalia Villota; Jose Lomas; Luis Miguel Camarero. Changes of turbidity during the oxidation of dihydroxylated benzenes by Fenton reagent and effect on dissolved oxygen. Desalination and Water Treatment 2018, 127, 2 -7.
AMA StyleNatalia Villota, Jose Lomas, Luis Miguel Camarero. Changes of turbidity during the oxidation of dihydroxylated benzenes by Fenton reagent and effect on dissolved oxygen. Desalination and Water Treatment. 2018; 127 ():2-7.
Chicago/Turabian StyleNatalia Villota; Jose Lomas; Luis Miguel Camarero. 2018. "Changes of turbidity during the oxidation of dihydroxylated benzenes by Fenton reagent and effect on dissolved oxygen." Desalination and Water Treatment 127, no. : 2-7.
Natalia Villota; Jose Lomas; Arrate Santaolalla; Luis Miguel Camarero. Kinetic modelling of colour changes in aqueous solutions of phenol oxidized by sono-Fenton technology. Desalination and Water Treatment 2018, 127, 32 -40.
AMA StyleNatalia Villota, Jose Lomas, Arrate Santaolalla, Luis Miguel Camarero. Kinetic modelling of colour changes in aqueous solutions of phenol oxidized by sono-Fenton technology. Desalination and Water Treatment. 2018; 127 ():32-40.
Chicago/Turabian StyleNatalia Villota; Jose Lomas; Arrate Santaolalla; Luis Miguel Camarero. 2018. "Kinetic modelling of colour changes in aqueous solutions of phenol oxidized by sono-Fenton technology." Desalination and Water Treatment 127, no. : 32-40.
Analysis of the kinetics of aqueous phenol oxidation by a sono-Fenton process reveals that the via involving ortho-substituted intermediates prevails: catechol (25.0%), hydroquinone (7.7%) and resorcinol (0.6%). During the oxidation, water rapidly acquires color that reaches its maximum intensity at the maximum concentration of p-benzoquinone. Turbidity formation occurs at a slower rate. Oxidant dosage determines the nature of the intermediates, being trihydroxylated benzenes (pyrogallol, hydroxyhydroquinone) and muconic acid the main precursors causing turbidity. It is found that the concentration of iron species and ultrasonic waves affects the intensity of the turbidity. The pathway of (hydro)peroxo-iron(II) complexes formation is proposed. Operating with 20.0-27.8mgFe(2+)/kW rates leads to formation of (hydro)peroxo-iron(II) complexes, which induce high turbidity levels. These species would dissociate into ZZ-muconic acid and ferrous ions. Applying relationships around 13.9mgFe(2+)/kW, the formation of (hydro)peroxo-iron(III) complexes would occur, which could react with carboxylic acids (2,5-dioxo-3-hexenedioic acid). That reaction induces turbidity slower. This is due to the organic substrate reacting with two molecules of the (hydro)peroxo complex. Therefore, it is necessary to accelerate the iron regeneration, intensifying the ultrasonic irradiation. Afterwards, this complex would dissociate into maleic acid and ferric ions.
Natalia Villota; Jose Lomas; Luis Miguel Camarero. Effect of ultrasonic waves on the water turbidity during the oxidation of phenol. Formation of (hydro)peroxo complexes. Ultrasonics Sonochemistry 2017, 39, 439 -445.
AMA StyleNatalia Villota, Jose Lomas, Luis Miguel Camarero. Effect of ultrasonic waves on the water turbidity during the oxidation of phenol. Formation of (hydro)peroxo complexes. Ultrasonics Sonochemistry. 2017; 39 ():439-445.
Chicago/Turabian StyleNatalia Villota; Jose Lomas; Luis Miguel Camarero. 2017. "Effect of ultrasonic waves on the water turbidity during the oxidation of phenol. Formation of (hydro)peroxo complexes." Ultrasonics Sonochemistry 39, no. : 439-445.
This study aims determining the effect that certain kind of water contaminants have on the changes of turbidity during their oxidation. Phenol is considered by its frequent presence in industrial discharges; meanwhile paracetamol is representative of emerging pollutants of pharmaceutical origin. Quite different results are observed in the turbidity changes during the oxidation of both pollutants that evolve following the kinetics of a reaction intermediate. The analysis of paracetamol and phenol degradation pathways reveals that operating conditions are important in the formation of intermediates that cause turbidity. The maximum turbidity levels are achieved operating at the ratios 12 mol HO per 100 mg contaminant. However the turbidity generated during the paracetamol oxidation only reaches a third of the intensity achieved with phenol. During the paracetamol degradation, the intermediates causing turbidity are similar to the ones found during the phenol decomposition. These species are generated during the initial minutes of oxidation and possess structures of large size and molecular weight. At the máximum turbidity point, muconic acid and hydroquinone are identified and found to coexist with other compounds such as pyrogallol and resorcinol. Therefore, the path involving metasubstitution would be the main originator of turbidity. It is noteworthy the rapid formation of muconic acid that coexists with resorcinol-like species. These compounds enable the establishment of hydrogen bond interactions that yield supramolecular structures.
Natalia Villota; Jose M. Lomas; Luis Miguel Camarero. Study of the paracetamol degradation pathway that generates color and turbidity in oxidized wastewaters by photo-Fenton technology. Journal of Photochemistry and Photobiology A: Chemistry 2016, 329, 113 -119.
AMA StyleNatalia Villota, Jose M. Lomas, Luis Miguel Camarero. Study of the paracetamol degradation pathway that generates color and turbidity in oxidized wastewaters by photo-Fenton technology. Journal of Photochemistry and Photobiology A: Chemistry. 2016; 329 ():113-119.
Chicago/Turabian StyleNatalia Villota; Jose M. Lomas; Luis Miguel Camarero. 2016. "Study of the paracetamol degradation pathway that generates color and turbidity in oxidized wastewaters by photo-Fenton technology." Journal of Photochemistry and Photobiology A: Chemistry 329, no. : 113-119.
This paper deals with the changes of turbidity that are generated in aqueous solutions of phenol when they are oxidized by using different Fenton technologies. Results revealed that if the Fenton reaction was promoted with UV light, the turbidity that was generated in the water doubled. Alternatively, the use of ultrasonic waves produced an increase in turbidity which initially proceeded slowly, reaching intensities eight times higher than in the conventional Fenton treatment. As well, the turbidity showed a high dependence on pH. It is therefore essential to control acidity throughout the reaction. The maximum turbidity was generated when operating at pH = 2.0, and it slowly decreased with increasing to a value of pH = 3.0, at which the turbidity was the lowest. This result was a consequence of the presence of ferric ions in solution. At pH values greater than 3.5, the turbidity increased almost linearly until at pH = 5.0 reached its maximum intensity. In this range, ferrous ions may generate an additional contribution of radicals that promote the degradation of the phenol species that produce turbidity. Turbidity was enhanced at ratios R = 4.0 mol H2O2/mol C6H6O. This value corresponds to the stoichiometric ratio that leads to the production of turbidity-precursor species. Therefore, muconic acid would be a species that generate high turbidity in solution according to its isomerism. Also, the results revealed that the turbidity is not a parameter to which species contribute additively since interactions may occur among species that would enhance their individual contributions to it. Analyzing the oxidation of phenol degradation intermediates, the results showed that meta-substituted compounds (resorcinol) generate high turbidity in the wastewater. The presence of polar molecules, such as muconic acid, would provide the structural features that are necessary for resorcinol to act as a clip between two carboxylic groups, thus establishing directional hydrogen bonds that would generate an adduct in the 2:2 ratio. In addition, some similarity is observed between the turbidity and the presence of dihydroxybenzoquinone. This molecule has a structure that could establish hydrogen bond links with the carboxylic groups in 1:2 ratio. Such supramolecular structures would possess high molecular weight and robustness that would hinder the passage of light through the water, generating high turbidity.
N Villota; Lomas Jm; Camarero Lm. Effect of substituted hydroxyl groups in the changes of solution turbidity in the oxidation of aromatic contaminants. Environmental Science and Pollution Research 2016, 24, 1105 -1112.
AMA StyleN Villota, Lomas Jm, Camarero Lm. Effect of substituted hydroxyl groups in the changes of solution turbidity in the oxidation of aromatic contaminants. Environmental Science and Pollution Research. 2016; 24 (2):1105-1112.
Chicago/Turabian StyleN Villota; Lomas Jm; Camarero Lm. 2016. "Effect of substituted hydroxyl groups in the changes of solution turbidity in the oxidation of aromatic contaminants." Environmental Science and Pollution Research 24, no. 2: 1105-1112.
This work completes the step of the mechanism of phenol oxidation, where the wastewater shows the maximum color levels, considering the formation of trihydroxybenzene rings and quinoidal compounds of hydroxylated nature as degradation intermediates. They have been determined experimentally by the stoichiometric ratios of oxidant to degrade phenol until the intermediate species generated during the oxidation (R = mol H2O2/mol C6H6O). Hence, catechol forms at R = 1.0, resorcinol at R = 1.3 and hydroquinone at R = 2.0. The addition of these ratios, R = 4.3, corresponds to the minimum dosage required to oxidize the initial phenol contained in the solution. p-benzoquinone is formed at R = 1.0. The formation of trihydroxylated rings with substituents in ortho-position (pyrogallol) and meta-(phloroglucinol), which makes them more unstable, needs a lower dosage of oxidant, R = 4.0, than the para-substituted (hydroxyhydroquinone), that requires R = 5.5. Muconic acid formation reaches its maximum at R = 6.0 while the formation of benzoquinones substituted by hydroxyl groups (dihydroxybenzoquinone) require R = 8.0. These results suggest that oxidation of p-benzoquinone would yield dihydroxybenzoquinone species, whereas muconic acid would be an oxidation byproduct of ortho- and meta-substituted species. The oxidation intermediates generated during the first steps of the oxidation pathway determine the color of oxidized wastewater, although iron species in solution may enhance its intensity. Maximum color is obtained at R = 4.0 and is produced by intermediates that are generated during the oxidation of pyrogallol and phloroglucinol-type compounds. A drastic decrease in color happens between R = 4.0 and 6.0 which corresponds to the formation of muconic acid. Finally, the color increases slightly at R greater than 7.0 which can be related to the formation of dihydroxylated benzoquinones. As the color and toxic compounds are degraded to biodegradable acids of colorless nature, the color intensity diminishes to colorless at R > 13.0.
N. Villota; Jose Lomas; L.M. Camarero. Nature of the degradation products of phenol which produce high levels of color in the wastewater oxidized in a photo-Fenton system. DESALINATION AND WATER TREATMENT 2016, 57, 28784 -28793.
AMA StyleN. Villota, Jose Lomas, L.M. Camarero. Nature of the degradation products of phenol which produce high levels of color in the wastewater oxidized in a photo-Fenton system. DESALINATION AND WATER TREATMENT. 2016; 57 (59):28784-28793.
Chicago/Turabian StyleN. Villota; Jose Lomas; L.M. Camarero. 2016. "Nature of the degradation products of phenol which produce high levels of color in the wastewater oxidized in a photo-Fenton system." DESALINATION AND WATER TREATMENT 57, no. 59: 28784-28793.
This work aims at establishing the contribution of the iron species to the turbidity of phenol solutions oxidized with photo-Fenton technology. During oxidation, turbidity increases linearly with time till a maximum value, according to a formation rate that shows a dependence of second order with respect to the catalyst concentration. Next, the decrease in turbidity shows the evolution of second-order kinetics, where the kinetics constant is inversely proportional to the dosage of iron, of order 0.7. The concentration of iron species is analysed at the point of maximum turbidity, as a function of the total amount of iron. Then, it is found that using dosages FeT=0-15.0 mg/L, the majority iron species was found to be ferrous ions, indicating that its concentration increases linearly with the dosage of total iron. This result may indicate that the photo-reaction of ferric ion occurs leading to the regeneration of ferrous ion. The results, obtained by operating with initial dosages FeT=15.0 and 25.0 mg/L, suggest that ferrous ion concentration decreases while ferric ion concentration increases in a complementary manner. This fact could be explained as a regeneration cycle of the iron species. The observed turbidity is generated due to the iron being added as a catalyst and the organic matter present in the system. Later, it was found that at the point of maximum turbidity, the concentration of ferrous ions is inversely proportional to the concentration of phenol and its dihydroxylated intermediates.
Natalia Villota; Luis Miguel Camarero; Jose Lomas; Jonatan Perez-Arce. The role of iron species on the turbidity of oxidized phenol solutions in a photo-Fenton system. Environmental Technology 2015, 36, 1855 -1863.
AMA StyleNatalia Villota, Luis Miguel Camarero, Jose Lomas, Jonatan Perez-Arce. The role of iron species on the turbidity of oxidized phenol solutions in a photo-Fenton system. Environmental Technology. 2015; 36 (14):1855-1863.
Chicago/Turabian StyleNatalia Villota; Luis Miguel Camarero; Jose Lomas; Jonatan Perez-Arce. 2015. "The role of iron species on the turbidity of oxidized phenol solutions in a photo-Fenton system." Environmental Technology 36, no. 14: 1855-1863.
Turbidity presented by phenol solutions oxidized with Fenton reagent shows the tendency of a first order intermediate kinetics. Thus, turbidity can be considered a representative parameter of the presence of intermediate oxidation species, which are generated along the decomposition of toxic and reluctant contaminants, such as phenol. Moreover, that parameter presents a linear dependence with the catalyst dosage, but is also determined by the initial contaminant load. When analyzing the oxidation mechanism of phenol, it is found that the maximum turbidity occurs when the treatment is carried out at oxidant to phenol molar ratios R = 4.0. These oxidation conditions correspond to the presence of a reaction mixture mainly composed of dihydroxylated rings, precursors of the muconic acid formation. The oxidation via "para" comprises the formation reactions of charge transfer complexes (quinhydrone), between the para-dihydroxylated intermediates (hydroquinone) and the para-substituted quinones (p-benzoquinone), which are quite unstable and reactive species, quickly decomposed into hydroxyhydroquinones. Working with oxidant ratios up to R = 6.0, the maximum observed value of turbidity in the oxidized solutions is kept almost constant. It is found that, in these conditions, the pyrogallol formation is maximal, what is generated through the degradation of ortho-species (catechol and ortho-benzoquinone) and meta-substituted (resorcinol). Operating with ratios over R = 6.0, these intermediates are decomposed into biodegradable acids, generating lower turbidity in the solution. Then, the residual turbidity is a function of the molar ratio of the ferrous ions vs. moles of oxidant utilized in the essays, that lets to estimate the stoichiometric dosage of catalyst as 20 mg/L at pH = 3.0, whereas operating in stoichiometric conditions, R = 14.0, the residual turbidity of water results almost null.
Natalia Villota; Luis Miguel Camarero; Jose Lomas; Jonatan Perez. Changes of turbidity during the phenol oxidation by photo-Fenton treatment. Environmental Science and Pollution Research 2014, 21, 12208 -12216.
AMA StyleNatalia Villota, Luis Miguel Camarero, Jose Lomas, Jonatan Perez. Changes of turbidity during the phenol oxidation by photo-Fenton treatment. Environmental Science and Pollution Research. 2014; 21 (21):12208-12216.
Chicago/Turabian StyleNatalia Villota; Luis Miguel Camarero; Jose Lomas; Jonatan Perez. 2014. "Changes of turbidity during the phenol oxidation by photo-Fenton treatment." Environmental Science and Pollution Research 21, no. 21: 12208-12216.
This study analyses the oxidation of phenol using Fenton reagent in presence of ultraviolet light, enhancing the mineralization capacity of the treatment. Phenol oxidation generates reaction intermediates more toxic and refractory than phenol itself. Thus, the reaction must be carried out under harder conditions, leading these compounds to biodegradable acids that can be dumped into public sewages. Then, this paper considers a complete kinetic modelling of the phenol oxidation stages, differentiating the formation rate of species generated through ortho, meta and para pathways. The model is based on a mechanism of series reactions, wherein a first step degrades into dihydroxylated intermediates (catechol, resorcinol and hydroquinone). A second stage leads to tri-hydroxylated rings (pyrogallol) and benzoquinones (o-benzoquinone and p-benzoquinone), and both species may coexist in the reaction mixture. Next, if conditions are sufficiently oxidizing, they decompose into biodegradable organic acids (muconic, formic or acetic acids). In this mechanism, the parallel reactions, due to the presence of the metal catalyst, are considered. So, on one hand, there is a formation of metal complexes between species ortho-substituted and ferric ions from the catalyst. On the other hand, there is a precipitation of part of the initial catalyst as ferric hydroxide, due to the presence of ultraviolet light, which is determined by the operation pH. Studies have been performed on the selectivity of the oxidation in function of the reaction conditions. Then, when operating with pH = 3.0, oxidation was favoured via ortho-substituted compounds. Treatment is advisable within Pho = 100–300 mg/L, being necessary to apply molar ratios of oxidant above R = 6.0 mol H2O2/mol C6H5OH to degrade these intermediates. Moreover, kinetic constants of formation of generated species are estimated, supposing that follows an evolution comparable to first-order reactions. Analysis checks that these kinetic constants present some relation to the operating conditions. In this way, a mathematical estimation is presented, showing the dependence of the kinetics on the parameters controlling the process (pH, initial concentration of phenol, oxidant molar ratio, catalyst dosage and temperature). As a result, the behaviour of the system can be predicted within the considered range.
Natalia Villota; Luis Miguel Camarero; Jose Maria Lomas; Mikel Legaristi. Kinetic Modelling of Photoconversion of Phenol by a Photo-Fenton Reagent and UV. International Journal of Chemical Reactor Engineering 2014, 12, 405 -416.
AMA StyleNatalia Villota, Luis Miguel Camarero, Jose Maria Lomas, Mikel Legaristi. Kinetic Modelling of Photoconversion of Phenol by a Photo-Fenton Reagent and UV. International Journal of Chemical Reactor Engineering. 2014; 12 (1):405-416.
Chicago/Turabian StyleNatalia Villota; Luis Miguel Camarero; Jose Maria Lomas; Mikel Legaristi. 2014. "Kinetic Modelling of Photoconversion of Phenol by a Photo-Fenton Reagent and UV." International Journal of Chemical Reactor Engineering 12, no. 1: 405-416.