1,252 research outputs found
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
“The First Thing Philosophers Have to Do Is to Learn”: An Interview with Martha C. Nussbaum
No full textMartha C. Nussbaum is internationally renowned for being one of the leading moral and political philosophers of our time, and is highly regarded for her work on the role of the emotions in moral and political reasoning. In this interview, in dialogue with her interlocutors, she discusses her work over the past four decades, and gives insights into her book in progress on opera and its relationship to liberal political ideals, The Republic of Love. In addition to declaring her love of Italian culture, she clarifies her stance on some contemporary issues, including the controversy on sex and gender, animal rights, the relationship between philosophy and natural sciences, and the importance of liberal arts and ancient Greek and Roman philosophy
Probing for new physics and detecting non-linear vacuum QED effects using gravitational wave interferometer antennas
No full textNew Physics with GW antenna used for QED vacuum probin
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
La tradizione manoscritta del messale ambrosiano : ricerche sulla formazione e sull'evoluzione di una tipologia libraria tra i secoli VII e XVI
No full textLe prime testimonianze manoscritte di libri per la celebrazione messa secondo il rito ambrosiano, ovverosia secondo il rito seguito dalla sede episcopale di Milano, risalgono al secolo VII, sebbene in forma frammentaria. I primi codici completi sono invece dei secoli IX-X e, pur avendo subito gli influssi delle riforme carolingie, presentano forme e testi peculiari milanesi. La tradizione manoscritta continua fino ai secoli XV-XVI, spenta dall’introduzione della stampa: mostra aggiunte e integrazioni, che mai però sovvertono il modello carolingio.
L’indagine prende avvio dallo studio dei manoscritti, scelti per distribuzione cronologica e importanza, e ne mette in luce le caratteristiche paleografiche, codicologiche, contenutistiche, onde meglio calarli nel contesto che li ha prodotti. Segue la sinossi del loro contenuto, disposta per circulum anni e commentata nel dettaglio nel successivo capitolo, in modo da mettere in luce le fonti e le caratteristiche dei formulari contenuti nei messali. Tutti gli elementi raccolti consentono così di tracciare una storia di questo libro liturgico sia nelle sue forme, sia nei suoi contenuti
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