Examinando por Autor "Molina, R."

Mostrando 1 - 13 de 13

Activity and resistance of iron-containing amorphous, zeolitic and mesoestructured materials for wet peroxide oxidation of phenol
(ELSEVIER, 2005) Calleja, G.; Melero, J.A.; Martínez, F.; Molina, R.
Iron containing materials have been prepared following several strategies of synthesis and using different silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials was evaluated on heterogeneous Fenton-type processes for the removal of phenol under mild reaction conditions (T=100º, P=0.1 MPa). Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions, by-products distribution (aromatics compounds and carboxylic acids) and degree of metal leached into the aqueous solution. The nature and local environment of iron species is strongly dependent on the synthetic route, which dramatically influences on their catalytic performance. Crystalline iron oxide species supported over mesostructured SBA-15 materials have demonstrated to be the most interesting catalysts for phenol degradation according to its high organic mineralization, low sensitive to be leached out and better oxidant efficiency for Fenton like reactions.
Advanced bio-oxidation of fungal mixed cultures immobilized on rotating biological contactors for the removal of pharmaceutical micropollutants in a real hospital wastewater
(Elsevier, 2021) Cruz del Álamo, A.; Pariente, M.I.; Molina, R.; Martínez, F.
Hospital wastewater represents an important source of pharmaceutical active compounds (PhACs) as contaminants of emerging concern for urban wastewater treatment plants. This work evaluates a fungal biological treatment of a hospital effluent before discharging in the municipal sewer system. This treatment was performed in rotating biological contactors (RBCs) covered with wooden planks in order to promote the attachment of the fungal biomass. These bioreactors, initially inoculated with Trametes versicolor as white rot fungi, have created biofilms of a diversified population of fungal (wood-decaying fungi belonging to Basidiomycota and Ascomycetes) and bacterial (Beta-proteobacteria, Firmicutes, and Acidobacteria) microorganisms. The mixed fungal/bacterial community achieved a stable performance in terms of carbon, nitrogen, and phosphorous reductions for 75 days of continuous operation. Moreover, a remarkable removal of pharmaceutical micropollutants was accomplished especially for antibiotics (98.4 ± 0.7, 83 ± 8% and 76 ± 10 for azithromycin, metronidazole and sulfamethoxazole, respectively). Previous studies have proven a high efficiency of fungi for the removal of microcontaminants as a result of advanced bio-oxidation processes mediated by oxidizing hydroxyl radicals. This study evidences the development of a stable fungal-bacterial mixed culture over wooden-modified RBCs for in-situ removal of pharmaceutical compounds of hospital wastewater under non-sterile conditions and non-strict temperature control, avoiding periodical fungal inoculation due to destabilization and displacement of fungal cultures by indigenous wastewater bacteria.
Comprehensive characterization of an oily sludge from a petrol refinery: A step forward for its valorization within the circular economy strategy
(Elsevier, 2021) Jerez, S.; Ventura, M.; Molina, R.; Pariente, M.I.; Martínez, F.; Melero, J.A.
Refinery treatment plants produce large quantities of oily sludge during the petroleum refining processes. The hazardousness associated with the disposal of these wastes, make necessary the development of innovative technologies to handle it adequately, linked to the concepts of circular economy and environmental sustainability. This work provides for the first time a methodology for the deep characterization of this kind of wastes and consequently new insights regarding its valorization. A review of works dealing with the characterization of this type of wastes has been addressed evidencing the complexity and variability of these effluents. The oily sludge under study contains a high concentration of Chemical Oxygen Demand of 196 g COD/L, a Total Kjeldahl Nitrogen of 2.8 g TKN/kg, a phosphorous content as PO43− of 7 g/kg, as well as a great presence of heavy metals in a different range of concentrations. This sludge is composed of three different phases: oily, aqueous and solid. The oily and the solid phases present high percentages of carbon content (84 and 26%, respectively), related to the presence of alkanes ranged from n-C9 to n-C44. Therefore, it could be possible their valorization by the synthesis of catalyst and/or adsorbents. A dark fermentation process could be also proposed for the oily phase to obtain H2 as an alternative energy source. Finally, the aqueous phase contains low carbon and nutrients concentration. A previous thermal pre-treatment applied to the oily sludge might increase nutrient and organic loading in the aqueous phase due to solid destruction, making this aqueous effluent suitable for a further conventional biological treatment.
Coupling membrane separation and photocatalytic oxidation processes for the degradation of pharmaceutical pollutants
(Elsevier, 2013) Martínez, F.; López-Muñoz, M.J.; Aguado, J.; Melero, J.A.; Arsuaga, J.; Sotto, A.; Molina, R.; Segura, Y.; Pariente, M.I.; Revilla, A.; Cerro, L.; Carenas, G.
The coupling of membrane separation and photocatalytic oxidation has been studied for the removal of pharmaceutical pollutants. The retention properties of two different membranes (nanofiltration and reverse osmosis) were assessed. Comparable selectivity on the separation of pharmaceuticals were observed for both membranes, obtaining a permeate stream with concentrations of each pharmaceutical below 0.5 mg/L and a rejected flux highly concentrated (in the range of 16-25 mg/L and 18-32 mg/L of each pharmaceutical for NF-90 and BW-30 membranes, respectively), when an initial stream of six pharmaceuticals was feeding to the membrane system (10 mg/L of each pharmaceutical). The abatement of concentrated pharmaceuticals of the rejected stream was evaluated by means of heterogeneous photocatalytic oxidation using TiO2 and Fe2O3/SBA-15 in presence of hydrogen peroxide as photo-Fenton system. Both photocatalytic treatments showed remarkable removals of pharmaceutical compounds, achieving values between 80 and 100 %. The nicotine was the most refractory pollutant of all the studied pharmaceuticals. Photo-Fenton treatment seems to be more effective than TiO2 photocatalysis, as high mineralization degree and increased nicotine removal were attested. This work can be considered an interesting approach of coupling membrane separation and heterogeneous photocatalytic technologies for the successful abatement of pharmaceutical compounds in effluents of wastewater treatment plants.
Crystallization mechanism of Fe-MFI from wetness impregnated Fe2O3-SiO2
(ELSEVIER, 2004) Melero, J. A.; Calleja, G.; Martínez, F.; Molina, R.; Lázár, K.
The crystallization mechanism of Fe-MFI zeolite synthesized from amorphous Fe2O3- SiO2 xerogels wetness impregnated with aqueous TPAOH solutions has been studied. Samples with different degrees of crystallinity were prepared and characterized by means of conventional techniques. Activity and stability of these iron-containing samples has been tested in the catalytic wet peroxide oxidation (CWPO) of phenolic aqueous solutions. The crystallization mechanism involves a partial dissolution of the initial xerogel to yield an amorphous material. Nucleation and growth of the MFI phase is effected by reorganisation of the amorphous phase, although crystal growth also involves the incorporation of iron and silicon species during the last stage of the crystallization. A highly crystalline Fe-silicalite material is obtained after 3 hours of synthesis at 170 ºC. Spectroscopic studies reveal that iron species are in framework positions (isomorphously substituted) in this highly crystalline material. In addition, the environment of Fe atoms as well as textural properties of the samples is dramatically modified along the crystallization affecting significantly to their catalytic activity and stability in CWPO processes.
Enhancement of the Advanced Fenton process (Fe0/H2O2) by ultrasound for the mineralization of Phenol
(ELSEVIER, 2012-02) Segura, Y.; Martínez, F.; Melero, J.M.; Molina, R.; Chand, R; Bremner, D.H.
In this study, a successful mineralization of phenol was achieved by means of coupling zero-valent iron (ZVI) particles, hydrogen peroxide and a short input of ultrasonic irradiation. This short Sono-Advanced Fenton process (AFP) provided a better performance of ZVI in a subsequent silent degradation stage, which involves neither extra cost of energy nor additional oxidant. The short input of ultrasound irradiation enhanced the activity of the Fe0/H2O2 system in terms of the TOC removal. Then, the TOC mineralization continued during the silent stage, even after the total consumption of hydrogen peroxide, reaching values of ca. 90% TOC conversions over 24 hours. This remarkable activity was attributed to the capacity of the ZVI/iron oxide composite formed during the degradation for the generation of oxidizing radical species and to the formation of another reactive oxidant species, such as the ferryl ion. The modification of the initial conditions of the sono-AFP system such as the ultrasonic irradiation time and the hydrogen peroxide dosage, showed significant variations in terms of TOC mineralization for the ongoing silent degradation stage. An appropriate selection of operation conditions will lead to an economical and highly efficient technology with eventual large-scale commercial applications for the degradation organic pollutants in aqueous effluents.
Heterogeneous catalytic Wet Peroxide Oxidation Systems for the Treatment of an Industrial Pharmaceutical Wastewater
(ELSEVIER, 2009) Melero, J.A.; Martínez, F.; Botas, Juan Ángel; Molina, R.; Pariente, M.I.
The aim of this work was to assess the treatment of a wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using a Fe2O3/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80ºC using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for a complete carbon depletion and initial pH of ca. 3 allow obtaining TOC degradation around 50% after 200 minutes of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55 hours of reaction. Furthermore, BOD5/COD ratio is increased from 0.20 up to 0.30, whereas the Average Oxidation Stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.
Heterogeneous photo-Fenton degradation of phenolic aqueous solutions
(ELSEVIER, 2005) Martínez, F.; Calleja, G.; Melero, J.A.; Molina, R.
A novel iron-containing mesostructured material has been successfully tested for the heterogeneous photo-Fenton degradation of phenolic aqueous solutions using near UV-visible irradiation (higher than 313 nm) at room temperature and close to neutral pH. This catalyst is a composite material that contains crystalline hematite particles embedded into the mesostructured SBA-15 matrix in a wide distribution of size (30 ¿ 300 nm) and well dispersed ionic iron species within the siliceous framework. The outstanding physicochemical properties make this material a promising photocatalyst leading to better activity than other unsupported iron oxides. An experimental design model has been applied to assign the weight of catalyst and hydrogen peroxide concentrations in the photo-Fenton processes over this particular material. The catalytic performance has been monitored in terms of aromatics and total organic carbon (TOC) conversions, whereas the catalyst stability was evaluated according to the metal leached into the aqueous solution. Hydrogen peroxide concentration plays an important role in the stability of the iron species, preventing their leaching out into the solution, in contrast to the effect shown in typical dark Fenton reaction. The homogeneous leached iron species result in very little contribution to the overall photocatalysis process. Catalyst loadings of 0.5 g/L and concentration of hydrogen peroxide close to the stoichiometric amount have yielded a total abatement of phenol and a remarkable organic mineralization.
Iron species incorporated over different silica supports for the Phenol
(ELSEVIER, 2007) Martínez, F.; Calleja, G.; Melero, J. A.; Molina, R.
Iron-containing catalysts have been prepared following different synthesis routes and silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials were assessed on the photo-Fenton degradation of phenolic aqueous solutions using near UV irradiation (higher than 313 nm) at room temperature and initial neutral pH. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions. Aromatic compounds and carboxylic acids as by-products coming from incomplete mineralization of phenol as well as the efficiency of each catalytic system in the use of the oxidant were also studied. Stability of the materials throughout the photo-Fenton reaction was evaluated in terms of metal leachibility. Activity and stability depend on the environment of iron species and features of silica support. The evolution of pH with the reaction time and their relationship with TOC degradation and leaching degree has been discussed. A nanocomposite material of crystalline iron oxides supported over mesostructured SBA- 15 material is shown the most successful catalyst for degradation of phenolic aqueous solutions by photo-Fenton processes, achieving an outstanding overall catalytic performance accompanied with a noteworthy stability.
Kinetic modeling of the first step of Mn2O3/MnO thermochemical cycle for solar hydrogen production
(Elsevier, 2012-12) Marugán, J.; Botas, J.A.; Molina, R.; Herradón, C.
This work reports the kinetic study of the first step of the Mn2O3/MnO thermochemical cycle for hydrogen production by water splitting. The reaction kinetics of Mn (III) oxide thermal reduction has been evaluated using dynamic thermogravimetric analysis at constant heating rate under nitrogen flow. This way the reaction rate can be described as a function of temperature and different kinetic models were fitted to the experimental data obtained from thermogravimetric experiments. A good fitting can be observed for each experiment, although a significant disparity in the values estimated for the Arrhenius parameters has been found (activation energies and pre-exponential factors). Unique values for the kinetic parameters have been calculated by application of a multivariate non-linear regression method for the simultaneous fitting of data from all the experiments carried out at different heating ramps. However, also in this case the values of the Arrhenius parameters are significantly different depending on the chosen kinetic equation. Optimal kinetic parameters have been finally calculated through the estimation of activation energy values by model-free isoconversional methods and using a rigorous multivariate nonlinear regression for the calculation of the model-dependant pre-exponential factors.
Nanocomposite Fe203/SBA-15: An efficient and stable catalyst for the catalytic wet peroxidation of phenolic aqueous solutions
(ELSEVIER, 2007) Melero, J. A.; Calleja, G.; Martínez, F.; Molina, R.; Pariente, M. I.
In this work, the catalytic wet peroxide oxidation of phenolic aqueous solutions over a novel Fe2O3/SBA-15 nanocomposite material was deeply studied. The catalytic performance was monitored in terms of aromatics and total organic carbon (TOC) removals. In order to reduce the major operation cost, significant operating reactions parameters that affect remarkably the overall catalytic performance of these processes, such as temperature and hydrogen peroxide concentration, were studied by means of a design of experiments. High temperature is necessary to obtain a fast and complete degradation of aromatic compounds. At 100ºC, moderate catalyst loading and hydrogen peroxide concentration (0.6 g/L and 75 % of stoichiometric amount for phenol mineralization, respectively) were enough to achieve a total removal of aromatic compounds and remarkable TOC mineralization under non-controlled pH conditions. Resistance of iron species to be leached out into the aqueous solution has been also carefully examined with the purpose of elucidating the influence of different reaction parameters (temperature, oxidant concentration and pH). A schematic view of the heterogeneous catalytic peroxidation of phenol over this novel catalyst has been proposed. Finally, the stability of the catalyst has been established by recycling studies.
Novel 3D electro-Fenton reactor based on a catalytic packed bed reactor of perovskite/carbon microelectrodes for the removal of carbamazepine in wastewater
(Elsevier, 2024-08) Cruz del Álamo, A.; Puga, A.; Dias Soares, C.M.; Pariente, M.I.; Pazos, M.; Molina, R.; Sanromán, M.A.; Martínez, F.; Delerue-Matos, C.
This presents the efficacy of a 3D-ElectroFenton (3D-EF) reactor with active perovskite/carbon black/PTFE microelectrodes for the removal of carbamazepine (CZP) present in wastewater. Incorporating particle microelectrodes in the reactor enhanced the electron transfer and improved the electrocatalytic efficiency, leading to a more effective CZP removal. The optimal operational conditions were meticulously determined, including current intensity (0.05 – 0.3 A) and particle loading (0 – 1.5 g), to optimize the process and minimize energy consumption. The findings reveal that a current intensity of 0.2 A was the most effective, achieving 90% of CZP removal in 60 min and 3.86 kWh/mg of CZP. A higher current intensity of 0.3 A significantly increased the energy consumption (6.02 kWh/mg of CZP) for a total and faster CZP removal. The 3D-EF reactor was also operated continuously with ultrapure water and real urban wastewater fortified with CZP. A remarkable 62% CZP removal after 96 h on continuous operation was achieved with urban wastewater. Physicochemical and electrochemical characterization of microelectrodes demonstrated their high mechanical integrity and chemical stability. Our study underscores the potential of a 3D-EF system as a promising advanced oxidation process to address the continuous removal of antidepressant carbamazepine as one of the more resistant micropollutants of emerging concern in wastewater treatment, offering hope for a more efficient and sustainable future
Treatment of an agrochemical wastewater by integration of heterogeneous catalytic wet hydrogen peroxide oxidation and rotating biological contactors
(Elsevier, 2013-06-15) Melero, J.A.; Pariente, M.I.; Siles, J.A.; Molina, R.; Botas, J.A.; Martinez, F.
The treatment of a non-biodegradable agrochemical wastewater has been studied by coupling of heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and rotating biological contactors (RBCs). The influence of the hydrogen peroxide dosage and the organic content of the wastewater (dilution degree) were studied. The CWHPO of the raw wastewater at 80 ºC and using a moderate amount of oxidant (0.23 gH2O2/gTOC) reduced significantly its total organic carbon content and increased its biodegradability. Likewise, the iron leaching of the heterogeneous catalyst (Fe2O3/SBA- 15) was less than 2 mg/L in the treated effluent. Under the best operating conditions, the resultant CWHPO effluent was successfully co-treated by rotating biological contactors (RBCs) using a simulated municipal wastewater with different percentages of the CWHPO effluent (2.5, 5 and 10 % v/v). The RBCs showed high stability for the treatment of the highest percentage of the CWHPO effluent, achieving total organic carbon (TOC) and total nitrogen (TN) reductions of ca. 78 % and 50 %, respectively. The integration of both processes on a continuous mode has been successfully accomplished for the treatment of the as-received agrochemical wastewater.