1,300 research outputs found
Jürgen Habermas, Nuovo mutamento della sfera pubblica e politica deliberativa, a cura di M. Calloni, trad. di L. Corchia e F.L. Ratti, Milano, Raffaello Cortina, 2023.
No full textIndice
Introduzione all’edizione italiana. Ripensare la sfera pubblica (Marina Calloni) VII
Prefazione 1
1. Un nuovo mutamento di struttura della sfera pubblica politica 3
2. Sulla democrazia deliberativa. Un’intervista 73
3. Che cosa significa “democrazia deliberativa”? Obiezioni e fraintendimenti 95
Sinossi
Con Storia e critica dell'opinione pubblica (1962), Habermas ha aperto nuovi orizzonti per gli studi sulla genesi e le trasformazioni della sfera pubblica politica. Seppur in modo non esplicito, il concetto di sfera pubblica ha accompagnato senza soluzione di continuità le sue opere successive. Habermas torna ora a interrogarsi sul nuovo mutamento di struttura della sfera pubblica, determinato da Internet e dai social media nel contesto di un ecosistema mediale, ibrido, decentrato e reticolare. Tale trasformazione sta incidendo sul funzionamento deliberativo degli ordinamenti democratici e sulla riproduzione simbolica del mondo della vita, con una frammentazione della sfera pubblica e la polverizzazione delle opinioni generali. Verrebbe così cancellato uno spazio collettivo di intermediazione, essenziale per la libera formazione della volontà politica, per la deliberazione democratica e per i nostri stessi processi di apprendimento e di riflessione
Stability of Organic Cations in Solution-Processed CH3NH3PbI3 Perovskites: Formation of Modified Surface Layers
No full textCalloni A, Abate A, Bussetti G, et al. Stability of Organic Cations in Solution-Processed CH NH PbI Perovskites: Formation of Modified Surface Layers. The Journal of Physical Chemistry C. 2015;119(37):21329-21335.We report on a combined X-ray and UV photoemission spectroscopy study (XPS and UPS) of organic–inorganic perovskites prepared from a solution of lead chloride (PbCl2) and methylammonium iodide (CH3NH3I). The XPS intensities are consistent with a pure iodide perovskite (CH3NH3PbI3), with no detectable chloride left. However, we found that the elimination of chloride results in residual methylamine molecules (CH3NH2) trapped within the perovskite crystal lattice. Furthermore, we show that vacuum annealing or sputtering induces the formation of a thin PbI2 layer at the crystal surface which acts as a surface barrier blocking electron transfer from the underlying perovskite film
Advanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters: homogeneous vs. heterogeneous photocatalytic processes
No full textAdvanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters: homogeneous vs. heterogeneous photocatalytic processes
Francesco Conte 1, Cristina Calloni 2, Ilenia Rossetti 3 and Gianguido Ramis 4*
1 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
2 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
3 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
4* DICCA, Università degli Studi di Genova, Genoa, Italy, presenting author, corr. author ([email protected])
INTRODUCTION
Textiles industries huge production determines a strong environmental impact: the yearly total impact per person is estimated to be 1.3 tonnes of raw material and over 100 m3 of water. Ca. 700,000 – 1,000,000 tons/years of dyes are produced and more than 280,000 tons are lost in the effluent and often remain as persistent pollutants. Heterogeneous and homogeneous phototreatments can be efficiently used as Advanced Oxidation Processes to degrade such contaminants and a comparison between different technologies has been carried out on the azo-dye Dystar’s Levafix Brilliant Red E-6BA.
EXPERIMENTAL
Oas a model molecule for this study because it is characterized by low biodegradability
TiO2 P25 was employed as a commercial nanostructured material supplied by Evonik and compared with TiO2 FSP, prepared through a homemade flame spray pyrolysis apparatus. Metallic co-catalysts were deposited over the surface by wet impregnation and then reduced at different temperature (Ag, Au, Pt, Pd, Fe).
The catalysts were characterised by XRD, N2 physisorption and DR-UV-VIS analyses.
The photo-degradation tests were carried out in different cylinder-type double-wall glass reactors of 300-1000 mL capacity, open to air and equipped with a suitable lamp in case of photocatalyzed processes.
The Fenton process was carried out either in light or dark conditions by adding Fe salts and H2O2 and compared with UV/H2O2 and Heterogeneous photodegradation processes with the above described catalysts.
The light sources employed were characterized by different emission wavelength and power output: a LED-type lamp (white light, 30 W, 2700 lm), an external UV lamp (200W, maximum emission at 365 nm) and two different low power immersed-UV lamp (125 W, maximum emission at 365 nm); natural sunlight. The average irradiance was measured for the different setups through a photo-radiometer sensitive to the UVA fraction and were 116 W/m2 in case of the external-UV lamp and respectively 60 and 260 W/m2 for the low irradiance (lamp 1) and high irradiance (lamp 2) immersed-UV lamp. The progress of the reaction was monitored by UV-Vis and Total Organic Carbon (TOC).
Toxicity tests on the treated solutions were also carried out using the Crustacean Daphnia magna.
RESULTS AND DISCUSSION
The fastest degradation process was Photo-Fenton with the highest power immersion UV lamp (10 min to 97.4% conversion), strictly followed by the UV/H2O2 process (20 min to 100% conversion). The degradation time increased with the other light sources, i.e. sun and LED, but overall, the total reaction time did not exceed 30 min. On the other hand, when it comes to the heterogeneous process, the titania synthetized via flame pyrolysis takes longer time to reach full conversion. At first glance it seems that the homogeneous treatment outperforms the heterogeneous ones, however, in the first case these results were achieved using a large amount of hydrogen peroxide, about 3.5 equivalents, which of course boost the reaction and lowers the time required to achieve a good conversion of the substrate.
Figure 9: Degradation of Levafix dye: comparison.
No organic carbon was detected after the treatment, except when employing gold deposited catalyst. Acute toxicity tests revealed that the Levafix Briliant Red resulted in a 48h-LC50 of 117 mg/L. The toxic response was dramatic in case of the solutions treated with UV/H2O2 and (Photo)Fenton processed, since a higher mortality of Daphnia magna specimens was observed due to the residual amounts of hydrogen peroxide. Overall, the best toxicity results were achieved in case of the samples treated with titania photocatalyst (P25), since the toxicity of the solutions was lower than the ones containing the bare dye.
CONCLUSION
Photo-degradation of Levafix Brilliant Red was compared for different AOPs. The homogeneous treatments were more efficient in the degradation of the selected dye, but the main advantages of employing solid nanostructured photocatalyst is that it is not compulsory to add hydrogen peroxide (low toxicity) and the catalyst can be recovered easily
Epitaxial thin films oxides on Fe: what happens when a low dimensional oxide grows on a highly reactive metal substrate?
No full textThe investigation of oxide films with a thickness of a few nanometers or below grown on another substrate is a scientific topic that has recently attracted a huge amount of experimental and theoretical research work [1].
In this contribution we shall focus on some of the recent advances in understanding the formation of transition metal oxide/Fe interfaces [2,3]. Fe can be considered on the one hand as a prototypical example of ferromagnetic material, and on the other hand as an example of a highly reactive metal. The former characteristic makes it particularly appealing for spintronic applications and magnetic storage media, while the latter makes the preparation of well-defined oxide/metal interfaces a difficult task. For this reason, despite the large body of literature focusing on the preparation and characterization of ultra-thin oxide films on inert materials such as noble and quasi noble metals, comparatively little is known about the atomic scale mechanisms driving the formation of the transition metal oxide/Fe interfaces.
In the first part of the talk we shall discuss the stabilization of single-layer-thick oxide films on Fe, by using selected examples involving the deposition of transition metals on the well-ordered and defect-free Fe(001)-p(1 × 1)O surface. This is characterized by one oxygen atom per surface unit cell which can be used as a reservoir for the stabilization and investigation of Fe-supported twodimensional transition metal oxides [4,5], avoiding at the same time the Fe oxidation occurring when more traditional preparation procedures (such as for instance metal deposition in a reactive oxygen atmosphere) are employed.
In the second part we shall discuss the growth of oxide films out of the interfacial layer, with particular emphasis on the growth mode leading at the same time to sharp interfaces, useful to correctly modeling the interfacial physical phenomena, and atomically flat surfaces, crucial to allow scanning probe microscopy studies down to the atomic scale.
References: [1] See e.g. S.Valeri and G. Pacchioni, eds., Oxide Ultrathin Films (Wiley-VCH Verlag, Weinheim,2011).
[2] M. Finazzi, L. Duò, and F. Ciccacci, Surf. Sci. Rep. 64, 139 (2009).
[3] M. Finazzi, L. Duò, and F. Ciccacci, eds., Magnetic Properties of Antiferromagnetic Oxide Materials: Surfaces, Interfaces and Thin Films (Wiley-VCH Verlag, Weinheim, 2010).
[4] A. Picone, G. Bussetti, M. Riva, A. Calloni, A. Brambilla, L. Duò, F. Ciccacci, and M. Finazzi, Phys. Rev. B 86, 075465 (2012).
[5] A. Picone, G. Fratesi, M. Riva, G. Bussetti, A. Calloni, A. Brambilla, M.I. Trioni, L. Duò, F. Ciccacci, M. Finazzi, Phys. Rev. B 87 (2013) 085403
Electronic and spectral properties of clean and C60-covered atom-thick Chromium oxide at the Fe(001) surface
No full textChemisorption of a single atomic layer of oxygen on the Fe(001) surface yields a highly ordered and reproducible benchmark substrate [1] for theoretical and experimental studies, and for the epitaxial growth of metal oxides, including atom-thick CrxOy layers, and hybrid interfaces with foreseen applications e.g. in organic spintronics.
This talk initially presents ab initio investigations that have supplemented microscopy and spectroscopy experiments of the electronic and magnetic properties of two-dimensional Chromium oxides of Cr3O4 and Cr4O5 stoichiometry grown on Fe(001), featuring antiferromagnetic magnetic configurations with underlying Fe(001) [2,3]. Despite Cr / CrO systems are notoriously difficult for mean field approaches, generalized-gradient results are found to explain most experimental findings, with a rigid shift of oxygen bands accounting for electronic correlation effects.
We eventually consider the effect of inserted Cr4O5 layers at the interface between the prototypical C60 organic semiconductor and Fe(001), which is shown to enhance the magnetic hybridization between the molecule and the surface through x-ray magnetic circular dichroism (XMCD) [4,5]. By means of ab initio calculation we characterize the local interface morphology, the magnetic configuration of the surface and the induced spin dependent electronic properties of the molecule, the latter reflecting the magnetic electronic properties of the surface at the relevant energy range. As seen from the substrate, adsorbates can influence the magnitude and even orientation of surface Cr magnetic moments. The interest in this interface is then twofold: on one side the thin magnetic oxide allows tailoring the magnetic properties of the organic layer, on the other side the adsorption of C60 can be envisioned as a tool to control the magnetic ordering of Cr atoms at the interface.
[1] A. Picone, M. Riva, A. Brambilla, A. Calloni, G. Bussetti, M. Finazzi, F. Ciccacci, L. Duò, Surface Science Reports 71, 32 (2016).
[2] A. Picone, G. Fratesi, M. Riva, G. Bussetti, A. Calloni, A. Brambilla, M. I. Trioni, L. Duò, F. Ciccacci, and M. Finazzi, Phys. Rev. B 87, 085403 (2013).
[3] A. Calloni, G. Fratesi, S. Achilli, G. Berti, G. Bussetti, A. Picone, A. Brambilla, P. Folegati, F. Ciccacci, and L. Duò, Phys. Rev. B 96, 085427 (2017).
[4] A. Brambilla, A. Picone, D. Giannotti, A. Calloni, G. Berti, G. Bussetti, S. Achilli, G. Fratesi, M. I. Trioni, G. Vinai, P. Torelli, G. Panaccione, L. Duò, M. Finazzi, and F. Ciccacci, Nano Lett. 17, 7440 (2017).
[5] A. Brambilla, A. Picone, S. Achilli, G. Fratesi, A. Lodesani, A. Calloni, G. Bussetti, M. Zani, M. Finazzi, L. Duò, and F. Ciccacci, Journal of Applied Physics 125, 142907 (2019)
Self-organized chromium oxide monolayers on Fe(001)
No full textThe growth of ultrathin epitaxial oxide films on metal supports is attracting
considerable scientific interest both
on a fundamental level and for potential technological applications.
Growth techniques such as reactive deposition (i.e., metal deposition in oxygen
atmosphere) and/or post-oxidation are typically applied, leading to ordered phases
and well defined oxide-metal interfaces on noble metal substrates. On the contrary,
when a more reactive metal, such as Fe, is used as a substrate for the nano-oxide
growth, these procedures fail to produce sharp metal/oxide interfaces. Indeed, during
the metal deposition in oxygen atmosphere, extensive and uncontrolled oxidation of
Fe occurs, preventing the stabilization of long-range ordered oxide monolayers.
An alternative route to obtain a sharp interface between a single layer of transition
metal oxide and a reactive
substrate may be to exploit the oxygen adsorbed on the surface before metal
deposition since, in this case, the
amount of oxygen available is well defined.
The well ordered and defect-free Fe(001)-p(1×1)O surface is an ideal template to
implement this strategy.
The surface is characterized by one oxygen atom per surface unit cell, which can be
used as a reservoir for
the stabilization of two-dimensional transition metal oxides.
In this contribution, by means of a combination of high resolution Scanning Tunneling
Microscopy images, Auger Electron Spectroscopy, and Density Functional Theory
calculations, we show how the Fe(001)-p(1 × 1)O surface can be used as a template
for the self assembly of two dimensional Cr oxides. Cr deposition on this surface
leads to two different phases, depending on the amount of deposited Cr. At 0.75 monolayers coverage a c(4 × 2) overlayer with Cr3O4 formal stoichiometry is
stabilized, while an overlayer with (???5 ×???5)R°27 symmetry and Cr4O5 stoichiometry
is obtained at slightly higher coverages [1].
Furthermore, the magnetic properties of these oxide monolayers are investigated by
means of X-ray magnetic circular dichroism.
References: [1] A. Picone, G. Fratesi, M. Riva, G. Bussetti, A. Calloni, A. Brambilla, M. I. Trioni, L.
Duò, F. Ciccacci, and M. Finazzi, Self-organized chromium oxide monolayers on
Fe(001), Phys. Rev. B 87, 085403 (2013
Efficiency comparison of advanced oxidation processes (AOPs) for the mineralization of azo-dyes in water
No full textEfficiency comparison of advanced oxidation processes (AOPs)
for the mineralization of azo-dyes in water
F. Contea, C. Callonia, A. Tripodia, G. Ramisb and I. Rossettia
a Chemical Plants and Industrial Chemistry Group, Dip. Chimica, Università degli Studi di Milano, CNR-ISTM and INSTM Unit Milano-Università, via C. Golgi 19, 20133 Milan, Italy;
b Dip. Ing. Chimica, Civile ed Ambientale, Università degli Studi di Genova and INSTM Unit Genova, via all’Opera Pia 15A, 16145 Genoa, Italy
The aim of this work was to find out a sustainable and scalable process in order to treat dye-rich wastewaters from textile industries and fully degrade these organic pollutants to non-harmful substances. Different chemical, photochemical and photocatalytic processes have been compared to find the most suitable for this application, either in terms of technical feasibility and with a look to the safety of the treated wastewaters.
The Dystar’s Levafix Brilliant Red E-6BA dye was used as a model molecule and treated through different advanced oxidation processes (APOs): H2O2/UV, Fenton and Photo-Fenton reactions, defined as homogeneous phase reactions, to be further compared with heterogeneous photocatalyzed processes. The use of heterogeneous titania may be advantageous since the catalyst can be separated and re-used after the treatment, in contrast with the iron salt used for Fenton reaction which forms sludges. Moreover, metallic co-catalysts can be deposed over TiO2 nanoparticles in order to tune the light harvesting properties and activity.
The various reaction parameters, such as pH, concentration of oxidant, quantity of Fe catalyst, type of light source (dark, LED, sunlight and UV) were changed and optimized to shorten the degradation time.
The best results were observed when using a low-power UV lamp directly immersed into the solution, as the time required to degrade 100 ppm solution of dye (pH 7, 25 °C, 36 mg/L of catalyst, 1 equivalent of oxidant) was ca. 10 minutes for both Photo-Fenton and UV/H2O2 processes, compared with 160 minutes required to complete the degradation in dark conditions. The reaction time almost doubled (20 min) when employing an external UV lamp, while both visible LED and solar light sources were comparable in terms of results (ca. 50 min), but the latter strictly depended on the weather conditions.
The treatment with 50 ppm of titania P25 was very effective when using an UV lamp directly immersed into the solution (irradiance = 260 W/m2), indeed more than 95% of the pollutant was degraded in ca. 40 min and we observed even better performance when adding hydrogen peroxide to the reactor (4 eq. H2O2, 8 min).
To conclude the feasibility assessment, the 48-LC50 values of the treated samples were determined performing the acute toxicity test using Daphnia magna to check the toxicity of the final products. The treated solutions were characterized by acute toxicity, even higher than the original dye when H2O2 was used. Since COD tests revealed that for most cases there was no residual organic carbon into the treated solution, the noxious effects were mainly attributed to the residues of hydrogen peroxide. This poses severe limits for the application of these technologies, at difference with heterogeneous photocatalytic processes, which may be slower, but by far safer, even when using nanostructured TiO2, which revealed no acute toxicity effect for the selected organisms
Development and comparison of advanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters
No full textDevelopment and comparison of advanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters G. Ramisa, F. Conteb, C. Callonib, A. Tripodib and I. Rossettib
a Dip. Ing. Chimica, Civile ed Ambientale, Università degli Studi di Genova and INSTM Unit Genova, via all’Opera Pia 15A, 16145 Genoa, Italy b Chemical Plants and Industrial Chemistry Group, Dip. Chimica, Università degli Studi di Milano, CNR-ISTM and INSTM Unit Milano-Università, via C. Golgi 19, 20133 Milan, Italy The aim of this work was to find out a sustainable and scalable process in order to treat dye-rich wastewaters from textile industries and fully degrade these organic pollutants to non-harmful substances. The Dystar’s Levafix Brilliant Red E-6BA dye was used as a model molecule and treated through different advanced oxidation processes (APOs): H2O2/UV, Fenton and Photo-Fenton reactions, defined as homogeneous phase reactions, to be further compared in part 2 with heterogeneous photocatalyzed processes. The use of heterogeneous titania may be advantageous since the catalyst can be separated and re-used after the treatment, in contrast with the iron salt used for Fenton reaction which forms sludges. Moreover, metallic co-catalysts can be deposed over TiO2 nanoparticles in order to improve the light harvesting properties and activity.
The reaction parameters, such as pH, concentration of oxidant, quantity of Fe catalyst, type of light source (dark, LED, sunlight and UV) were evaluated and optimized to complete the degradation in the shortest time. The best performances were observed when using a low-power UV lamp directly immersed into the solution, as the time required to degrade 100 ppm solution of dye (pH 7, 25 °C, 36 mg/L of catalyst, 1 equivalent of oxidant) was ca. 10 minutes for both Photo-Fenton and UV/H2O2 processes, compared with 160 minutes required to complete the degradation in dark conditions. The reaction time almost doubled (20 min) when employing an external UV lamp, while both visible LED and solar light sources were comparable in terms of results (ca. 50 min), but the latter strictly depended on the weather conditions.
The treatment with 50 ppm of titania P25 is very effective when using an UV lamp directly immersed into the solution (irradiance = 260 W/m2), indeed more than 95% of the pollutant was degraded in ca. 40 min and we observed even better performance when adding hydrogen peroxide to the reactor (4 eq. H2O2, 8 min).
To conclude, the 48-LC50 values of the treated samples were determined performing the acute toxicity test using Daphnia magna to check the toxicity of the final products. The treated solutions were characterized by acute toxicity, even higher than the original dye when H2O2 was used, however COD tests revealed that for most cases there was not organic carbon into the solution and the noxious effects were mainly attributed to the residues of hydrogen peroxide
Casimir apparatuses in a weak gravitational field
No full textWe review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the resulting regularized and renormalized energy-momentum tensor is covariantly conserved, while the trace anomaly vanishes if the massless field is conformally coupled to gravity. Conformal coupling also ensures a finite Casimir energy and finite values of the pressure upon parallel plates. These results have been extended to an electromagnetic field subject to perfect conductor (hence idealized) boundary conditions on parallel plates, by various authors.The regularized and renormalized energy-momentum tensor has been evaluated up to second order in the gravity acceleration. In both the scalar and the electromagnetic case, studied to first order in the gravity acceleration, the theory predicts a tiny force in the upwards direction acting on the apparatus. This effect is conceptually very interesting, since it means that Casimir energy is indeed expected to gravitate, although the magnitude of the expected force makes it necessary to overcome very severe signal-modulation problems
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