86,908 research outputs found
Teologia morale
No full textA quasi trent’anni dalla pubblicazione del Dizionario di teologia morale, il Gruppo Editoriale San Paolo ha deciso di realizzare un nuovo testo, completamente rinnovato. Il volume accoglie l’invito di papa Bergoglio al rinnovamento sapiente e coraggioso che è richiesto dalla trasformazione missionaria di una Chiesa in uscita.
UN NUOVO DIZIONARIO che si rifà ai criteri indicati dalla Veritatis gaudium di papa Francesco per la ricerca e lo studio della teologia.
UN’OPERA ENCICLOPEDICA che fornisce adeguate chiarificazioni e precisi orientamenti di fronte alle complesse e inquietanti questioni che assillano la coscienza dell’uomo di questo nostro tempo.
OLTRE 80 AUTORI, 140 VOCI, 1272 PAGINE
ARRICCHISCONO IL DIZIONARIO una proposta di lettura sistematica e una mappa concettuale, una bibliografia essenziale e un dettagliato indice analitico. L'opera è a cura di Paolo Benanti, Francesco Compagnoni, Aristide Fumagalli, Giannino Piana
Schema tettonico dei rilievi carbonatici compresi nel F. 367 "Tagliacozzo" alla scala 1:50.000
No full textOsservazioni sulla tettonica e dati sulla litostratigrafia dei rilievi carbonatici compresi nel F. 367 "Tagliacozzo" alla scala 1:50.000
No full textInnovative Photoreactors to remove N-containing pollutants from water
No full textThe photooxidation of ammonia and photoreduction of nitrates have been investigated in semibatch mode, developing a suitable process to achieve the desired selectivity to innocuous N2. Proper photoreactor prototypes have been tested for both applications, together with process design.
1. Scope
The development of efficient processes in photocatalysis is a challenging task. In particular, N-containing pollutants1, such as inorganic ammonia, nitrites and nitrates, and some organic N-containing compounds (dyes, pesticides, drugs, etc.)2, are harmful contaminants for drinking water, inducing acute and/or chronic diseases, especially affecting infants and children. Furthermore, when released in waste waters, they contribute to eutrophication, or possibly contaminate ground water. This is particularly relevant in agriculturally intensive zones and in the case of some relevant industrial processes involving e.g. nitration reactions.
In the present work, we developed innovative photocatalytic processes for the abatement of N-compounds, focusing on selectivity towards innocuous N2, to be applied for the treatment of waste waters to meet legislative specifications. The photocatalytic performance of the samples, to be correlated with nanomaterials properties, has been checked for the photoreduction of nitrate ions and the photooxidation of ammonia and organic N-containing compounds by means of two semi-batch photoreactors, specifically designed and optimized for this application.
2. Results and discussion
Different photocatalysts have been tested and compared. TiO2 has been prepared in nanosized form by using an innovative flame pyrolysis (FP) approach, able to synthesise single or mixed oxide nanoparticles, characterized by homogeneous particle size and good phase purity. This method is suitable for continuous one-step synthesis of oxides3. The apparatus includes a nozzle/burner, which is co-fed with oxygen and with an organic solution of the oxide precursors. The organic solvent acts as fuel for the flame, whereas oxygen is the comburent and the dispersing agent. The TiO2 samples was prepared from a solution of Titanium(IV)-isopropylate (Aldrich, pur. 97 %) in xylene and propionic acid. The burner was fed with a flow rate of 2.2 mL/min of the solution and 5 L/min of O2. The pressure drop across the nozzle was set to 1.5 bar. Several metals such as Pd and Ag were added as co-catalysts with a 0.1-0.5 wt% concentration by wet impregnation from a solution of nitrate precursors.
Photocatalytic reduction of NO3− and oxidation of NH3/NH4+ in water were carried out in a specifically designed Pyrex reactor, with a top quartz window (Figure 1). The catalysts were suspended in an aqueous solution of NH4Cl (0.2M) or NaNO3 (0.006M) and the suspension was stirred using a magnetic stirrer. The reaction suspension was thoroughly degassed and then exposed to He. The reactor was operated in semi-batch mode: the solution containing the pollutant to be photoconverted was added at the beginning of the reaction in batch mode, whereas a gas stream continuously flowed through the reactor. The gas was composed by He during the conditioning-outgassing phase preliminary to every measurement. He was fed in continuous mode also during the nitrate photoreduction tests, whereas it was substituted by synthetic air (80 vol% He + 20 vol% O2) during the ammonia photooxidation experiments. A trap for ammonia, possibly stripped from the reactor, was placed downstream.
Comparison with commercial nanostructured TiO2 supports revealed several differences. The TiO2 sample prepared by FP exhibited higher activity with respect to the commercial sample, achieving ca. 20 % conversion after 5 h, without indication of decay or deactivation. By contrast, the commercial sample was less active and most of all its activity was rapidly ruled out. Some induction period was observed, due to the need of sample conditioning upon irradiation. The most interesting point is that no trace of nitrites or nitrates was observed, confirming a full selectivity to the desired product, i.e. molecular N2.
The photoreduction of nitrates was also tested over the same samples. Very low conversion (<5%) was achieved with pure TiO2 catalysts, whereas Pd doping improved conversion by ca. one order of magnitude under the same experimental conditions. The key problem remained process selectivity: 100% to the undesired NH3 for the undoped photocatalyst, max 30% for the Pd-doped sample prepared by FP.
Figure 1. Scheme of the photocatalytic plant set up
3. Conclusions
An innovative photoreactor has been set up allowing to achieve the photoreduction of nitrates and the photooxidation of ammonia in semibatch mode. Its configuration, to be further optimised as for geometry and mixing, is suitable for scale up, easily implements immobilised photocatalysts and is ready to use with direct sunlight. These first results on both reactions let us conclude that a two step process can be designed to cope with the insufficient selectivity to N2 during the nitrate photoreduction step. The ammonia produced is removed during a second, fully selective step of photooxidation. The flame pyrolysis procedure is a viable technique for the preparation of either bare or metal-doped semiconductors in nanosized form, to be used for the photocatalytic abatement of inorganic N-containing pollutants in waste or drinking waters. Even if a photoreactor with external irradiation is less efficient than one base on immersion lamps, it is much more suitable for scale up and most of all for the direct application with solar light. Sufficiently high ammonia conversion was achieved during photooxidation in semibatch confirguration, with 100 % selectivity to N2.
The financial support of Fondazione Cariplo (Italy) through the measure “Ricerca sull’inquinamento dell’acqua e per una corretta gestione della risorsa idrica”, project “DEN - Innovative technologies for the abatement of N-containing pollutants in water”, grant no. 2015-0186, is gratefully acknowledged.
References
1. Compagnoni, M.; Ramis, G.; Freyria, F. S.; Armandi, M.; Bonelli, B.; Rossetti, I. Photocatalytic Processes for the Abatement of N-Containing Pollutants from Waste Water. Part 1: Inorganic Pollutants. J. Nanosci. Nanotechnol. 2017, in press.
2. Freyria, F. S.; Armandi, M.; Compagnoni, M.; Ramis, G.; Rossetti, I.; Bonelli, B. Catalytic and Photocatalytic Processes for the Abatement of N-Containing Pollutants From Wastewater . Part 2 : Organic Pollutants. J. Nanosci. Nanotechnol., 2017, in press.
3. Compagnoni, M.; Lasso, J.; Di Michele, A.; Rossetti, I. Flame Pyrolysis Prepared Catalysts for the Steam Reforming of Ethanol. Catal. Sci. Technol. 2016, 6247-6256
Metal modified TiO2 for CO2 photoreduction in unconventional conditions
No full textCO2 photoreduction, a growing field in green catalysis, shows great potentialities to avoid fossil fuels exploitation and to obtain C-based solar fuels through a sustainable process using water as a reductant and light irradiation as only energy input [1]. However, many efforts need to be made to have a substantial breakthrough to increase the efficiency of the whole process. To pursue this aim, different strategies can be followed, such as reaction conditions implementation and photocatalyst formulation.
Process efficiency is strictly dependent on chosen photocatalytic materials. In particular titanium dioxide, the most commonly used material, needs to be modified in order to boost light harvesting and increase photoactivity [2]. In this work, TiO2 was modified in order to increase electron mobility on photocatalytic surface. In particular, copper oxide was introduced as a co-catalyst and gold nanoparticles as surface plasmonic agents.
Some of the authors reported that unconventional conditions are able to increase solar fuels production from CO2 photoreduction in liquid phase, enhancing in particular CO2 absorption in aqueous media and tuning selectivity to desired products [3]. A novel pressurized liquid phase reactor was employed to study photocatalytic activity of these materials in liquid phase and reaction conditions were chosen in order to enhance CO2 absorption in liquid phase. In photocatalytic tests it was observed the formation of different liquid and gaseous products such as formic acid, formaldehyde, methanol, methane and hydrogen. The different materials provide a significant difference in both activity and product distribution. Photocatalytic behaviours were correlated to different physicochemical properties that were investigated though several techniques.
References
[1] O. Ola, M. Maroto-Valer, Journal of Photochemistry and Photobiology C: Photochemistry Reviews 24 (2015) 16-42
[2] A. Olivo, V. Trevisan, E. Ghedini, F. Pinna, C.L. Bianchi, A. Naldoni, M. Signoretto, Journal of CO2 Utilization 12 (2015) 86-94
[3] I. Rossetti, A. Villa, M. Compagnoni, L. Prati, G. Ramis, C. Pirola, C.L. Bianchi, W: Wang, D. Wang, Catalysis Science and Technology 5 (2015) 4481 - 448
Innovative Photoreactors for unconventional sustainable processes
No full textIntroduction
The development of new photoreactor configurations is a fundamental research topic for the transition from the lab-scale to the industrial application. Two main challenging processes were studied: i) the photocatalytic abatement of N-containing pollutants from waste water; ii) CO2 photoreduction to chemicals and fuels.
The release of significant amounts of nitrates, nitrites and ammonia in waste waters, either deriving from industrial or agricultural activities, creates a big condern due to their health effects and their action as nutrients causing eutrophication. Their abatement through conventional methods is largely inefficient. In addition, a relatively new source of N-containing organic pollutants is related to the increasing use of drugs, which are more and more released in urban areas. A photocatalytic continuous or semibatch technology is here proposed in order to effectively remove such contaminants from water. The attention is mainly focused on photoreactor design. The same approach has been applied to another very challenging process, i.e. the photocatalytic reduction of CO2, which is here carried out in an innovative photoreactor operating at high pressure (up to 20 bar) [1,2].
Materials and Methods
TiO2, either commercial or prepared through a flame pyrolysis process has been used as semiconductor. It has been added with Au, Ag, Pt or Pd with different loading. Characterisation of the materials has been carried ot by physisorption, XRD, DR-UV-Vis, FT-IR, TPR.
The photocatalytic tests have been performed on two different types of photoreactors. The first is a continuously stirred photoreactor that can be either operated in batch, semibatch or continuous mode, with external irradiation. This has been employed at atmospheric pressure, with variable temperature and catalyst loading for the photocatalytic abatement of N-containing compounds. A completely different concept of photoreactor has been developed for the photoreduction of CO2, which operates up to 20 bar, 90°C either in batch or continuous mode.
Results and Discussion
In this research, we show case studies of novel concepts of photoreactors developed by our group [1,2]. In addition nanostructured photocatalysts were prepared and tested for the abatement of N-containing compounds, focusing on selectivity towards innocuous N2. Part of the photocatalysts have been prepared in nanosized form by using an innovative flame pyrolysis (FP) approach, able to synthesise in one step single or mixed oxide nanoparticles, characterized by homogeneous particle size and good phase purity. Particle size ranged between 5 and 60 nm, depending on synthesis conditions. Doping of the sample with different metals (0.1-0.5 wt%) was also investigated. The FP procedure proved an interesting method for the preparation of nanostructured Ti-based photocatalysts. Ca. 2 orders of magnitude higher activity with respect to the literature has been achieved during the photoreduction of CO2 at high pressure. Productivity as high as 102 mmol h−1kgcat−1for H2, 16537 mmol h−1kgcat−1 for formaldehyde and 2954.37 mmol h−1kgcat−1 for formic acid were achieved when using bare TiO2 at 7 bar. The addition of Au further improved the productivity and turned the products distribution towards CH4 and CH3OH.
The FP semiconductors showed much more active also for the photooxidation of ammonia and the photoreduction of nitrates.
Figure 1. Sketch of one of the photoreactors used in this work.
Significance
Photocatalysis is gaining increasing importance. The development of photoreactors and their optimization for each specific application is less addressed than the development of innovative materials. In some cases here discussed, practically relevant conversions can only be achieved by using unconventional operating conditions.
References
1. Rossetti, I., Villa, A., Compagnoni, M., Prati, L., Ramis, G., Pirola, C., Bianchi, C.L., Wang, W., Wang, D., Catal. Sci. Technol. 5, 4481 (2015)
2. Galli, F., Compagnoni, M., Vitali, D., Pirola, C., Bianchi, C., Villa, A., Prati, L., Rossetti, I., Appl. Catal. B: Environmental, 200, 386 (2016
Steam reforming of bioethanol, effect of substrate concentration and purity
No full textA new process for hydrogen production has been proposed based on ethanol steam reforming. Ni-based catalysts have been developed with various techniques and revealed very active and selective for this reaction. Bioethanol of different origin and purity has been tested for this application revealing the possibility to optimise the separation procedure
Le Brecce della Renga (Monti Simbruini): un esempio di sedimentazione controllata dalla tettonica
No full textA simple duplex-PCR protocol for routine diagnosis and follow up of canine leishmaniasis.
No full textThe introduction of PCR has efficiently improved diagnosis of canine leishmaniasis. In order to provide a robust, efficient and reliable diagnostic method, a duplex PCR assay targeting the Leishmania infantum kDNA minicircle and the canine GAPDH gene as inner control was designed. Sensitivity of the assay reached 0.15 parasites/ml blood. Development, testing and application of this system on a group of 10 dogs during therapy administration (60 days) are also described. Six dogs (out of eight that have been showing a positive PCR result on peripheral blood during the study) were tested negative at day 62, indicating a reduction of parasitaemia at the end of the treatment period. All the animals had a positive PCR on lymph node aspirate both at the beginning and at the end of treatment. These findings seem to suggest that, in order to test therapy efficacy, PCR on whole blood could be a useful assay in dogs that have a positive PCR at the beginning of the treatment, while PCR positivity on lymph nodes lasts longer than the observation period during therapy administration. The presence of the GAPDH inner control band efficiently contributed to prevent false negatives, by highlighting samples affected by haemoglobin inhibition or inappropriate DNA isolation. Z9
Mutilazioni e culture : aspetti antropologici, in Il confronto interculturale: dibattiti bioetici e pratiche giuridiche
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