Our researchers

Francisco Javier Peñas Esteban

Most recent scientific publications (since 2010)

Authors: De Diego Díaz, Beatriz; Peñas Esteban, Francisco Javier; Fernández Rodríguez, Juana (Autor de correspondencia)
ISSN 0959-6526  Vol. 280  Nº P2  2021  pp. 124479
Lignocellulosic residues are a widely available energy resource, but their conversion into biogas through biomethanation may be hindered by a chemical structure with strong bonds. A strategy based on temperature-phased anaerobic digestion (TPAD) is here applied to optimize anaerobic digestion of artichoke as a representative lignocellulosic waste. The experiments consist of a first thermophilic stage conducted at 55 °C (7 and 5 days), followed by a second mesophilic stage at 35 °C. In addition, for comparison, single-stage temperature trials are carried out within the most common conditions for biomethanation (mesophilic at 35 °C, and thermophilic at 55 °C), as well as at the intermediate range (42 °C). In general, biomethanation of artichoke residues under TPAD configuration provides better performance than single-stage systems. Particularly, the best performance is observed for the TPAD arrangement using a thermophilic phase of 7 days. Thus, at this optimal configuration, volatile solids (VS) removal of 54%, and biogas and methane yields of 442 mL/g-VS and 375 mL-CH4/g-VS were reached, respectively. Moreover, a kinetic model coupling biogas generation and substrate consumption has been applied. Good agreement is found for both variables in each system tested. The calculated non-biodegradable substrate (S¿) is lower in TPAD systems (mean 49.6%) compared with that of single-stages (average 53.9%).
Authors: Peñas Esteban, Francisco Javier (Autor de correspondencia); Romo Hualde, Ana; Isasi Allica, José Ramón; et al.
ISSN 1226-086X  Vol. 75  2019  pp. 93 - 99
This paper examines the long-term application of a cyclodextrin hydrogel sorbent in multiple sorption-desorption cycles. Aqueous phenol was the target pollutant, whilst methanol, ethanol and isopropanol were chosen as eluents. The experimental results were well described by empirical models: the breakthrough curves by a two-parameter dose-response equation, and the elution curves by a pulse peak equation with two independent parameters. The differences in polarity of solvents produced sorbent fragmentation, particularly marked for isopropanol and considerably lower for methanol, and therefore a progressive increase in mass-transfer coefficients. In addition, a dual approach was developed from the proposed breakthrough model to address the mass transport of sorbate within the packed beds. The first one defines an average mass-transfer coefficient as representative for each complete sorption cycle, whereas a time-profile of this coefficient is deduced in the second method. A sorption capacity of 29.6 mg-phenol/g-sorbent was found in the working conditions.
Authors: Peñas Esteban, Francisco Javier (Autor de correspondencia); Sevillano Vaca, Xabier; Peñas, M. I.;
ISSN 1369-703X  Vol. 151  2019  pp. 107308
This work explores the behavior of a fluidized-bed bioreactor, packed with a hydrogel carrier of cyclodextrin-based polymer, under transient shock-loading events to evaluate its robustness and stability. Fourteen input rectangular pulses with different steps (6-24 times the baseline concentration) and duration (0.5-8 times the hydraulic residence time) were applied and the dynamic responses measured. A new shock-loading index is defined to quantify the combined effect of the influent concentration increase and the perturbation duration. The shock-loading index is directly proportional to the extra amount of phenol removed, to the additional oxygen consumed in the shock pulse, and to the time to return to baseline conditions. A simple model was developed to predict the effluent phenol concentration under pulsed shock-loading events. It assumes that a continuous-flow complete-mix system without diffusional mass transfer resistance in the biofilm. In addition, substrate adsorption is modeled using a simple concept based on the constant-pattern theory, while substrate biodegradation is described by the Haldane model. In spite of its conceptual simplicity, the model provides a pragmatic approach predicting a good match for data obtained during overload events (R-2 = 0.9810). The best-fitting parameters obtained were mu(M) = 0.166 +/- 0.007 d(-1), K-S = 8.62 +/- 0.46 mg/L, and K-I = 95.3 +/- 3.8 mg/L.
Authors: Figueroa-Pizano, M. D.; Vélaz Rivas, Itziar (Autor de correspondencia); Peñas Esteban, Francisco Javier; et al.
ISSN 0144-8617  Vol. 195  2018  pp. 476 - 485
The freezing-thawing is an advantageous method to produce hydrogels without crosslinking agents. In this study chitosan-poly(vinyl alcohol) (CS-PVA) hydrogels were prepared by varying the freezing conditions and composition, which affect the final characteristics of the products. The swelling degree, morphology, porosity, and diflunisal drug loading, as well as the drug release profiles were evaluated. The hydrogel swelling ratio was found to be mainly affected by the CS content, the number of freezing cycles and the temperature. SEM micrographs and porosity data confirm that pore size increases with the chitosan content. However, the use of either lower temperatures or longer freezing times, results in higher porosity and smaller pores. The drug release times of the CS-PVA hydrogels were as long as 30 h, and according to the mathematical fitting, a simple diffusion mechanism dominates the process. Moreover, a mathematical model predicting the hydrogels physical and structural behavior is proposed.
Authors: De Diego Díaz, Beatriz; Fernández Rodríguez, Juana (Autor de correspondencia); Vitas Pemán, Ana Isabel; et al.
ISSN 1385-8947  Vol. 334  2018  pp. 650 - 656
Barley malt and sloe are two raw materials used in the production of beer and pacharan (a Spanish spirit drink), respectively. These organic wastes have been used as substrate of anaerobic digestion to assess the effect of temperature (35 degrees C and 55 degrees C) and thermal pretreatment (80 degrees C for 1.5 h). Viable microbiological isolates have also been identified through metabolic tests and a kinetic model which includes biogas generation and volatile solids (VS) removal has been proposed. Temperature studies on barley malt yielded higher productivities at 55 degrees C (the ratio of produced biogas volume per VS consumed was 119% higher than that at 35 degrees C), but similar VS removal (0.9% less elimination at 55 degrees C). On the other hand, sloe digestion was more effective at 35 degrees C (biogas/VS-consumed ratio 252% higher than that at 55 degrees C), while VS elimination can be considered the same. Attending to the effect of thermal pretreatment on productivity, barley malt showed no improvement while sloe was enhanced (144% at 35 degrees C and 160% at 55 degrees C). Kinetic modelling fits to the experimental results, showing differences in maximum specific growth rate of biomass according with the temperature conditions. In all cases the adjustment was good (R-2 > 0.96). Microbiological characterization identified bacterial population, both strict and facultative anaerobes.
Authors: De Diego Díaz, Beatriz; Cerdan, J. M. A.; Peñas Esteban, Francisco Javier; et al.
ISSN 0960-3085  Vol. 110  2018  pp. 120 - 125
Different wastes treated together can be the supplement of nutritional deficiencies for the microorganisms involved in anaerobic codigestion (AcoD). In this study, the presence of macromolecules and trace elements on AcoD of agricultural waste was assessed. An extra nutrients solution that plays a key role in the microbiological metabolism was used at three different conditions: mesophilic (35 degrees C), intermediate (42 degrees C) and thermophilic (55 degrees C). The main results showed that at 35 degrees C in the presence of nutrients, biogas production reached 1.5-fold the production of biogas without them. Additionally, productivity was 1.9 times higher than that for the process without nutrients. Also, 42 degrees C without nutrients posed an interesting approach due to the uncommon use of this intermediate temperature, which has been demonstrated to be worth considering (55% of VS removal and 7.4 L-biogas). The AcoD at 55 degrees C showed that biogas production also surpassed 10.2 L with nutrients and that mL-CH4/g-VS were 1.2-fold of that obtained for the process without extra solution. Results for each temperature indicate that the nutrients solution contributes to AcoD. Furthermore, 35 degrees C, the most widespread temperature range at industrial scale, was the temperature at which the impact of nutrients was more remarkable. A deeper knowledge of AD nutritional limitations according to temperatures can optimize the industrial process in order to get better biogas yields and biomass removal. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Authors: Peñas Esteban, Francisco Javier; Safont Resardi, Bárbara
ISSN 0930-7516  Vol. 40  Nº 1  2017  pp. 64 - 70
A draft-tube spouted-bed (DTSB) reactor was equipped with an auxiliary aeration device to provide air into the annular region and thereby improve the oxygen transfer efficiency. The effects of the total air flow rate and its distribution between spout and annulus, the liquid phase viscosity (water and carboxymethyl cellulose solutions), and the solid holdup (glass and cyclodextrin polymer beads) on the oxygen transfer efficiency were discussed. The oxygen transfer coefficient increased with the air flow rate and the ratio of air flowing through the annulus, whereas it decreased with increasing viscosity and solid holdup. A correlation was proposed to predict the transfer coefficient in DTSB reactors with primary and auxiliary aeration. A good fitting was achieved between the experimental data and those estimated with the model.
Authors: Rioja, N.; Zorita, S.; Peñas Esteban, Francisco Javier (Autor de correspondencia)
ISSN 0926-3373  Vol. 180  2016  pp. 330 - 335
Photocatalysis employing TiO2 nanoparticles was studied to assess the effect of aqueous matrix nature in the degradation of clofibric acid (CFA) under UV-A radiation. Aeroxide TiO2-P25 at 0.50 g/L was the most effective catalyst among those tested, with a CFA degradation of 98.5% after 15 min. The CFA photodegradation in environmental waters (tap, mineral, river and recycled wastewater) and in the presence of inorganic (NaCl, FeCl3, FeCl2, AlCl3, CaCl2, Al2(SO4)3, Fe2(SO4)3, Na2SO4, NaHCO3, and Na2CO3) and organic compounds (humic acids, and a surfactant) commonly found in real waters was compared to that obtained in pure water. In general, the removal efficiency decreased with inorganic salts, especially with sulfates and carbonates (>70% deactivation), and also in environmental waters (>90%). A general kinetic model has been developed to describe the CFA photodegradation depending on the type and concentration of substances present in water. The first-order kinetic constants were estimated by defining a characteristic parameter for each ion species tested in the aqueous matrix. High correlation (R2 > 0.99 in most cases) was observed between experimental CFA concentrations and those predicted by the model.
Authors: Rioja Leal, N.; Benguria, P.; Peñas Esteban, Francisco Javier; et al.
ISSN 0944-1344  Vol. 21  Nº 19  2014  pp. 11168 - 11177
This work explores the competitive removal of pharmaceuticals from synthetic and environmental waters by combined adsorption-photolysis treatment. Five drugs usually present in waterways have been used as target compounds, some are pseudo-persistent pollutants (carbamazepine, clofibric acid, and sulfamethoxazole) and others are largely consumed (diclofenac and ibuprofen). The effect of the light source on adsorption of drugs onto activated carbons followed by photolysis with TiO2 was assessed, being UV-C light the most effective for drug removal in both deionized water and river water. Different composites prepared from titania nanoparticles and powdered activated carbons were tested in several combined adsorption-photocatalysis assays. The composites prepared by calcination at 400 °C exhibited much better performance than those synthesized at 500 °C, being the C400 composite the most effective one. Furthermore, some synthetic waters containing dissolved species and environmental waters were used to investigate the effect of the aqueous matrix on each drug removal. In general, photocatalyst deactivation was found in synthetic and environmental waters. This was particularly evident in the experiments performed with bicarbonate ions as well as with wastewater effluent. In contrast, tests conducted in seawater showed adsorption and photocatalytic degradation yields comparable to those obtained in deionized water.
Authors: San José, M. J.; Álvarez, S.; Peñas Esteban, Francisco Javier; et al.
ISSN 1385-8947  Vol. 238  Nº Supl. 1  2014  pp. 227 - 233
In order to determine the optimum operation conditions for thermal exploitation of fruit-tree pruning wastes in conical spouted bed combustors, operation maps for gas-solid flow regimes have been obtained from the experimental hydrodynamic study of beds of inert material (sand) in conical spouted bed contactors at high temperatures. To this end, minimum spouting and minimum dilute spouting (jet spouted bed) velocities and maximum bed pressure drop have been obtained for different systems. The effects of particle size and gas inlet temperature has been also studied. Combustion of fruit-tree pruning wastes has been successfully carried out in batch mode in a conical spouted bed combustor, with high combustion efficiencies, for gas inlet temperatures from 350 to 550 degrees C. Radial and axial temperature profiles have been measured both in uniform beds of inert material and also in beds composed of mixtures of sand and combusting wastes.
Authors: San José, M. J., (Autor de correspondencia); Alvarez, S.; Garcia, I.; et al.
ISSN 0263-8762  Vol. 92  Nº 4  2014  pp. 672 - 678
Clean technology of spouted bed is applied to paper industry wastes for energy valorization of de-inking sludge by combustion in a temperature range from 500 to 700 degrees C. The stable operating conditions for beds of different types of inert material (silica sand) have been tested in spouting regime over a wide range of operating conditions. The radial and axial temperature profiles of sand beds have been measured to improve the combustion efficiency of wastes. Thereafter, that sand providing the higher bed temperature has been applied as the fluidization material for combustion of papermaking sludge using a mass ratio of 2:1 (dry basis). The optimal conditions for the inlet air flow rate and temperature have been determined experimentally by maximizing the combustion efficiency and minimizing the amount of volatile compounds in the flue gas.
Authors: San José, M.J.; Alvarez, S.; Peñas Esteban, Francisco Javier; et al.
ISSN 0009-2509  Vol. 100  2013  pp. 413 - 420
De-watering of sludge wastes from pulp and paper industry has been studied using a conical spouted bed dryer. Influence of operating parameters such as the presence of a non-porous draft tube, the entrainment zone height, the draft tube diameter to gas inlet diameter ratio and waste moisture content on bed stability have been investigated for drying temperatures ranged from room temperature up to 140 degrees C. In addition, cycle time distribution of particles was determined for different experimental conditions. The drying time to reach given moisture content of the material decreased with increasing both gas inlet diameter and temperature. Although the use of the draft tube slightly raised drying time, it enhanced the uniformity of bed moisture content of treated wastes. The minimum gas spouting velocity required to reach the stable spouted bed regime was found to increase with both higher stagnant bed height and moisture content. The operation with a draft tube narrowed the frequency distribution of particle cycle times, the more the smaller the height of entrainment zone. Moreover, at the same experimental conditions, cycle times were longer when working with the draft tube. Therefore, the conical spouted bed dryer with a non-porous draft tube has been proven to be an effective pre-treatment for handling of sludge wastes from paper industry.
Authors: Ruiz de Ojeda Basurto, Luis María; Peñas Esteban, Francisco Javier
ISSN 1466-8564  Vol. 20  2013  pp. 191 - 197
Microwave blanching of green beans (Phaseolus vulgaris L.) was explored as an alternative to conventional hot-water blanching. Batches of raw pods were treated similarly to an industrial process employing a hot-water treatment but using a microwave oven for blanching. The effects of microwave processing time and nominal output power on physical properties (shrinkage, weight loss, texture, and color), enzyme activities (guaiacol peroxidase, L-ascorbate peroxidase, and catalase), and ascorbic acid content of pods were measured and modeled by first-order kinetics. Inactivation of peroxidase (POD) was the best indicator to assess the efficiency of microwave-blanching of green beans. No significant differences in product quality were found between hot-water blanched and microwaved pods at optimal processing conditions. Furthermore, since shorter processing times and higher ascorbic acid retention were found, microwave processing of green beans can be a good alternative to conventional blanching methods. Industrial relevance: Microwave blanching of green bean pods has been proved as a reliable alternative method to the conventional heating process used in the vegetable canning industry. The overall quality of the product processed by microwave heating under optimal conditions was comparable to that of the current industry process. The microwave treatment of pods, in addition to an effective enzyme inactivation in less processing time, led to a better retention of ascorbic acid.
Authors: San José, M. J.; Alvarez, S.; García, I.; et al.
Journal: FUEL
ISSN 0016-2361  Vol. 110  2013  pp. 178 - 184
In order to determine the behavior of a new conical spouted bed combustor for the thermal exploitation of wastes of pruning of vineyards by combustion, a hydrodynamic study has been carried out with homogenous beds wastes of pruning of vineyards, the evolution of the different regimes and the stable operation conditions have been determined. Beds consisting of vine shoots have been dried for improving combustion. The success of the combustion of wastes of vineyards pruning in a conical spouted bed combustor has been proven based on combustion efficiency values.
Authors: Sevillano Vaca, Xabier; Isasi Allica, José Ramón; Peñas Esteban, Francisco Javier
ISSN 0268-2575  Vol. 87  Nº 3  2012  pp. 402 - 409
BACKGROUND: Because of the lower fluidization energy required and the protection against shock loading and starvation due to their sorption capacity, light adsorbents such as hydrogels could be used as biofilm carrier media in fluidized bed bioreactors for wastewater processing. This work explores the feasibility of a cyclodextrin hydrogel as biomass support to degrade phenol under extremely low-nitrogen availability and under nitrogen amendments. RESULTS: Phenol removal capacity was low (mean 0.589 kg m(-3) day(-1)) under extreme nitrogen-limited conditions (mean C : N ratio 3830). A pulsed nitrogen amendment increased the elimination capacity (up to 1.97 kg m(-3) day-1) controlling the biofilm thickness. An 8-h nitrogen pulse had a highly efficient long-term effect removing 93.5 mg-C mg(-1)-N in 300 h. The continuous nitrogen amendment enhanced the elimination capacity (up to 5.84 kg m(-3) day-1) although rapidly increasing the biomass growth. The inhibiting phenol concentration was smaller during the nitrogen-limited period (below 100 mg L-1) than in the nitrogen-amendment periods (140 mg L-1). Low liquid velocities were needed to fluidize the bioparticles (less than 3.1 mm s(-1)) during the entire experimentation. CONCLUSION: This work shows that a fluidized-bed bioreactor with mixed culture on cyclodextrin-based particles can be operated for long periods at extreme nitrogen limitation, and that a limited nitrogen supply with periodic pulsed amendments would be adequate for controlling the biofilm thickness.
Authors: Safont Resardi, Bárbara; Vitas Pemán, Ana Isabel; Peñas Esteban, Francisco Javier
ISSN 1369-703X  Vol. 64  2012  pp. 69 - 75
A draft-tube spouted bed bioreactor was developed to investigate the microbial degradation of aqueous phenol using a cyclodextrin-based support material. Bacteria from activated sludge were acclimated to phenol in a continuous stirred tank bioreactor, and then immobilized onto the hydrogel particles within the spouted bed bioreactor. Microorganisms obtained under different operating conditions in both bioreactors were isolated and characterized. Batch phenol degradation assays performed on isolated dominant strains showed that Acinetobacter baumannii was the most resistant to phenol. Microbial population distribution in bioreactors was not only affected by phenol concentration, but also by oxygen availability, the system configuration and the presence of intermediates formed during phenol metabolization. A maximum elimination capacity of 2.79 kg-phenol/m(3) d was achieved in the spouted bed bioreactor, with Comamonas acidovorans being the dominant strain during high degradation periods.
Authors: Fernández Rodríguez, Juana; De Diego Díaz, Beatriz; Peñas Esteban, Francisco Javier
Book title:  Book of proceedings : VIII international scientific agriculture symposium AGROSYM 2017
2017  pp. 1886 - 1891
Anaerobic digestion (AD) is becoming one of the most feasible and efficient options for agroindustrial waste management. However, this kind of waste can contain certain substances from the industrial activity, which could potentially inhibit or, at least, modify the biomethanization process. Pesticides are widely used in agricultural activities. Mancozeb is an ethylene dithiocarbamate fungicide with broad spectrum used in crops. It reacts with and inactivates sulfhydryl groups of aminoacids and enzymes of fungal cells, disrupting of respiration, lipid metabolism and production of energy. Tefluthrin is a synthetic pyrethroid insecticide used to control a wide range of soil pests. It causes neurotoxicity and is a sodium channel modulator. This paper assesses the influence of the presence of mancozeb and tefluthrin on thermophilic (55°C) anaerobic co-digestion (carrot, cabbage, green pea, artichoke and fava and broad bean) of synthetic agroindustrial waste. The main results show that the pesticides improve the biomethanization process referred to generation of biogas (123%), consumption of volatile solid -VS- (18%), removal of chemical oxygen demand (5%) and yield of biogas measured like mL biogas/ VS consumed (117%), between other parameters. Anaerobic codigestion on presence of pesticides seems feasible and improved in comparison with the codigestion without these substances.
Authors: De Diego Díaz, Beatriz; Cerdán, J. M. A.; Peñas Esteban, Francisco Javier; et al.
Book title:  Book of proceedings : VIII international scientific agriculture symposium AGROSYM 2017
2017  pp. 1892 - 1896
Anaerobic codigestion has shown to be feasible to manage organic waste. Different wastes treated together can be the supplement of nutritional deficiencies for the microorganisms involved. In this study, the presence of acromolecules and trace elements on anaerobic codigestion of agricultural waste has been assessed. An extra nutrients solution containing elements, which play a key role in the anaerobic microbiological metabolism, was used at three different temperature conditions: mesophilic (35°C), intermediate (42°C) and thermophilic (55°C). The main results showed that at 35°C in the presence of nutrients, biogas production reached 6.2L, almost 1.5-fold the production of biogas without them. Additionally, productivity was 359.3mL-CH4 / g-VS, which is 1.9 times higher than that for the process without nutrients. At 42°C up to 55% of VS were eliminated and more than 10.0L-biogas were produced, while biomethanization without extra nutrients solution only reached 7.4L. The anaerobic codigestion at 55°C showed that biogas production also surpassed 10.2L in the presence of nutrients and 146.99mL-CH4 / g-VS were obtained, being these results 1.2-fold those obtained for the process without extra solution. Results for each temperature showed that the nutrients solution could contribute to the biomethanization process of codigestion waste. Furthermore, 35°C was the temperature range at which the impact of nutrients was more remarkable.
Authors: San José, M. J.; Alvarez, S.; Peñas Esteban, Francisco Javier; et al.
Book title:  Proceedings of the World Congress on Engineering 2012
Vol. 3  2012  pp. 1506 - 1511
The influence of the contactor angle, gas inlet diameter, particle diameter, length of the draft tube and height of the entrainment zone on the average cycle time in a novel conical spouted bed dryer with a draft tube has been analyzed by a two-level factorial experimental design to optimize the drying process at low temperature. The effect of these factors has been determined by a statistical analysis. An empirical correlation to calculate average cycle time in a novel conical spouted bed dryer with a draft tube has been proposed.
Authors: San José, M. J.; Alvarez, S.; Peñas Esteban, Francisco Javier; et al.
Book title:  Proceedings of the World Congress on Engineering 2012
Vol. 3  2012  pp. 1645 - 1650
In order to optimize the drying process at low temperature, the influence of geometric factors and operating conditions on drying time of wet coarse particle of sludge in a conical spouted bed dryer has been analyzed by means of a factorial experimental design. The effect of the geometric factors and operating conditions on drying time has been determined by a statistical analysis. Operation regimes of beds consisting of wet coarse particles in a conical spouted bed dryer have been determined by pressure drop fluctuations at inlet gas temperatures from room temperature up to 120 ºC. Results of drying modelling for beds of coarse particle wastes at different regimes have been verified through some experimental drying time of sludge.
Authors: Peñas Esteban, Francisco Javier; Isasi Allica, José Ramón
Book title:  Handbook of hydrogels: properties, preparation & applications
2010  pp. 341 - 364
Authors: Peñas Esteban, Francisco Javier; Isasi Allica, José Ramón
Book title:  Advances in Chemical Engineering
2010  pp. 175 - 186
Authors: Gamazo de la Rasilla, Carlos Manuel, (Coordinador); Sánchez Gómez, Susana, (Coordinador); Camacho Peiró, Ana Isabel, (Coordinador); et al.

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