Marta I Litter | Butex (original) (raw)

Papers by Marta I Litter

Procedia Materials Science, 2015

The aim of this work is to obtain porous titanium dioxide with good efficiency for photocatalytic... more The aim of this work is to obtain porous titanium dioxide with good efficiency for photocatalytic environmental applications. TiO 2 coatings were obtained by anodic spark deposition, at constant applied potential (150 V), using a platinum cathode and 0.5 M sulfuric acid as electrolyte. Samples of titanium Grade 2 were used as substrate, metallographically prepared until 1 μm diamond surface finishing. The variables of the process were temperature (25 and 40 °C) and anodization time (5 and 10 min). Samples obtained at 40 °C showed a higher current density than those obtained at 25 °C and the potential reached by these samples was lower than those obtained at 25 °C. These results are attributed to an increased electrolyte conductivity. Optical microscopy images of the oxides obtained at 40 ºC showed heterogeneity in color, indicating a non-uniform oxide thickness. This coincides with the images obtained by scanning electron microscopy that revealed "valleys" where the material did not present porosity. On the other hand, the oxides obtained at 25 °C showed a complete homogeneous porous structure. The average pore diameter was reduced with the increased oxidation time and temperature of the electrolyte. An increase of the crystalline anatase phase was observed with an increase of the anodization time; besides, rutile formation was observed, probably due to the final potential achieved by the samples.

Journal of Photochemistry and Photobiology A: Chemistry, 2002

In the present work, three commercially available TiO 2 -catalysts, namely Degussa P25, Sachtlebe... more In the present work, three commercially available TiO 2 -catalysts, namely Degussa P25, Sachtleben Hombikat UV100 and Millennium TiONA PC50, were platinised by a photochemical impregnation method in two ratios of platinum deposits (0.5 and 1 wt.%). The physical characterisation of the new synthesised catalysts was carried out by measurements of the BET-surface area, the light absorption properties and the adsorption of the model compounds. The photocatalytic activities of these samples were determined using three different model compounds: EDTA, 4-chlorophenol (4-CP), and dichloroacetic acid (DCA). While in the case of EDTA its disappearance was studied, total mineralisation was measured for 4-CP and DCA. In all cases, the photocatalytical activity was found to increase with rising amounts of Pt, e.g., the photonic efficiency for DCA degradation increased from 12.2% for pure Hombikat UV100 to 32.1% for Hombikat UV100/0.5 wt.% Pt and to 42.7% for Hombikat UV100/1 wt.% Pt. Promising results were also achieved for the total mineralisation of 4-CP. The photonic efficiency rised from 0.82% using unmodified PC50 to 1.14% with PC50/0.5 wt.% Pt (zero-order kinetics assumed in all cases). Similar results were obtained with the other new synthesised catalyst samples and for the model compound EDTA. No immediate relationship between the photocatalytic activity of the catalyst samples and their physical properties (surface area, adsorption of pollutants, absorption of light) could be observed.

Applied Catalysis A: General, 1999

Samples of iron-doped titania containing different amounts of Fe (0.5–5 wt%) prepared from TiCl 4... more Samples of iron-doped titania containing different amounts of Fe (0.5–5 wt%) prepared from TiCl 4 and Fe(III) acetylacetonate by a sol–gel method were tested as photocatalysts under near-UV irradiation for EDTA oxidation and for Cr(VI) reduction. Their efficiency has been ...

Journal of Photochemistry and Photobiology A: Chemistry, 2002

Two commercial samples, namely Degussa P-25 and Sachtleben Hombikat UV 100, and platinized modifi... more Two commercial samples, namely Degussa P-25 and Sachtleben Hombikat UV 100, and platinized modifications of these samples have been tested comparatively as photocatalysts for EDTA oxidation and for Cr(VI) reduction in the absence and in the presence of EDTA. Platinized photocatalysts were prepared by photoimpregnation of H 2 PtCl 6 on TiO 2 by prolonged irradiation in the presence of methanol. Only slight differences in efficiency were found between both pure commercial forms, except for the Cr(VI) reduction in the presence of EDTA, where Hombikat UV 100 samples were more active. Platinized Hombikat UV 100 was found to be less active for Cr(VI) reduction in water. The concentration of dissolved molecular oxygen was crucial for EDTA oxidation and had no influence on Cr(VI) reduction. From kinetic profiles, initial photonic efficiencies (ζ ) and conversion degrees have been calculated. Platinization did not improve Cr(VI) reduction but increased the initial photonic efficiency for EDTA oxidation. However, after prolonged irradiation, the conversion of EDTA was lower employing platinized samples instead of pure samples. The effect of platinum on titania was analyzed on the basis of proposed mechanisms.

Water science and technology : a journal of the International Association on Water Pollution Research, 2004

In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes ... more In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes has been performed: a) a homogeneous system with Fe(III)-NTA (1:1 complex), b) a TiO2/Fe(III)-NTA heterogeneous system. In both cases, NTA appears to play a positive role in the photochemical reaction. In the homogeneous system, the iron salt is the only absorbing species and is proved to be able to photoinduce 4-CP degradation ([4-CP] = 0.1-0.2 mM, [FeNTA] = 0.3-0.9 mM, pH 4, lambda = 365 nm). The progress of the reaction was positively affected by the FeNTA concentration, and the reaction kept going even after the total disappearance of FeNTA. However, 4-CP complete degradation requires the presence of oxygen, otherwise the reaction stops. In the heterogeneous system ([4-CP] = 2.0 mM, [FeNTA] = 1.0-2.0 mM, [TiO2] = 0.1 and 1.0 g L(-1), pH 3, lambda = 300-400 nm), an important effect of the complex on the degradation extent and on the initial reaction rate can be seen, which overcomes t...

Photochemical & Photobiological Sciences, 2010

Chromium(VI) reduction photoinduced by iron(III) nitrilotriacetate (FeNTA) was investigated under... more Chromium(VI) reduction photoinduced by iron(III) nitrilotriacetate (FeNTA) was investigated under monochromatic excitation. 313 nm was used as the irradiation wavelength in order to minimize the absorption of the light by chromium(VI): 91% of the photons were absorbed by FeNTA at pH = 7.0. Quantum yields of FeNTA and chromium(VI) disappearance and iron(II) formation were measured at pH 2.0, 4.0 and 7.0. In all the cases, chromium(VI) reduction follows first order kinetics with maximum efficiency at pH 2.0. The observed rate constant is proportional to FeNTA concentrations up to a maximum of 6.0 ¥ 10 -4 mol L -1 . The effect of oxygen was also investigated. If there is no large pH effect and no effect of oxygen on the quantum yields of chromium(VI) and FeNTA disappearance, the pH strongly influences the nature of the reduced chromium species. At pH 2.0, only chromium(III)was detected, whereas at pH 4.0 and 7.0 no chromium(III) resulting from chromium(VI) reduction was observed. Chromium(V) is supposed to be formed and stabilized by the chelating groups of NTA or NTA photoproducts.

The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which... more The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which ethyl or methyl 2,3,5,6-tetra-O-benzoyl-o-giuconate (5 and 6) crystallized after treatment with ethanol or methanol, respectively. These esters *Research Member of the ConseJo National de Investigaclones Clentlficas y T&ucas Carbohyd. Res., 14 (1970) 103-107 1. 0. DFFiRRAR I, R. M. DE LED-, B. MATSUJ3JR0, M. I. LITTER

Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2006

Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste tr... more Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, heterogeneous photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and/or the overall efficiency. This review addresses the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents. These combinations increase the photoprocess efficiency by decreasing the reaction time in respect to the separated operations or they decrease the cost in respect of heterogeneous photocatalysis alone, generally in terms of light energy. Depending on the operation coupled with heterogeneous photocatalysis, two categories of combinations exist. When the coupling is with ultrasonic irradiation, photo-Fenton reaction, ozonation, or electrochemical treatment, the combination affects the photocatalytic mechanisms thus improving the efficiency of the photocatalytic process. When the coupling is with biological treatment, membrane reactor, membrane photoreactor, or physical adsorption, the combination does not affect the photocatalytic mechanisms but it improves the efficiency of the overall process. The choice of the coupling is related to the type of wastewater to be treated. A synergistic effect, giving rise to an improvement of the efficiency of the photocatalytic process, has been reported in the literature for many cases.

h i g h l i g h t s UV-vis photocatalytic reduction of uranyl is revisited. Systems with nitrate ... more h i g h l i g h t s UV-vis photocatalytic reduction of uranyl is revisited. Systems with nitrate and perchlorate are the best for U(VI) removal. Acetate plays a negative role in U(VI) removal. In the absence and presence of 2-propanol main reduction mechanism is e CB À attack.

Ecotoxicology and Environmental Safety, 2015

Toxicity of a Cr(VI) solution before and after treatment by TiO2 heterogeneous photocatalysis (HP... more Toxicity of a Cr(VI) solution before and after treatment by TiO2 heterogeneous photocatalysis (HP) was performed with AMPHITOX bioassay. Changes in toxicity on Rhinella arenarum larvae for 10-d were monitored after exposure to an untreated Cr(VI) solution and to the same solution after HP treatment. The HP treatment of a 41.60mgL(-1) Cr(VI) solution reduced to 37.5% the concentration of the metal ion. A 10-fold reduction in toxicity at acute exposure (72h) and 150-fold reduction in toxicity after 240h was found. Further, the LOEC value increased from 0.001% for the untreated solution to 0.153% after HP treatment. Moreover, the safe concentration in untreated solution corresponded to 0.0001% sample, and it was 0.01% after the treatment, i.e., 100 times higher. A saving of water of about 100,000L per L of effluent would be possible through dilution to allow safer concentrations for discharge; the saving would reach the highest value (1,000,000L per L) at 240h. Sub-lethal effects were completely absent in larvae exposed to the treated solution. The AMPHITOX test allowed to detect chronic effects at low Cr concentrations, i.e. at environmentally relevant levels.

Science of The Total Environment, 2015

Four million people in Argentina are exposed to arsenic contamination from drinking waters of sev... more Four million people in Argentina are exposed to arsenic contamination from drinking waters of several center-northern provinces. A systematic review to examine the geographical distribution of arsenic-related diseases in Argentina was conducted, searching electronic databases and gray literature up to November 2013. Key informants were also contacted. Of the 430 references identified, 47 (mostly cross-sectional and ecological designs) referred to arsenic concentration in water and its relationship with the incidence and mortality of cancer, dermatological diseases and genetic disorders. A high percentage of the water samples had arsenic concentrations above the WHO threshold value of 10μg/L, especially in the province of Buenos Aires. The median prevalence of arsenicosis was 2.6% in exposed areas. The proportion of skin cancer in patients with arsenicosis reached 88% in case-series from the Buenos Aires province. We found higher incidence rate ratios per 100μg/L increment in inorganic arsenic concentration for colorectal, lung, breast, prostate and skin cancer, for both genders. Liver and skin cancer mortality risk ratios were higher in regions with medium/high concentrations than in those with low concentrations. The relative risk of mortality by skin cancer associated to arsenic exposure in the province of Buenos Aires ranged from 2.5 to 5.2. In the north of this province, high levels of arsenic in drinking water were reported; however, removal interventions were scarcely documented. Arsenic contamination in Argentina is associated with an increased risk of serious chronic diseases, including cancer, showing the need for adequate and timely actions.

The Journal of Physical Chemistry C, 2008

Similarly to alizarin molecules, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonate (alizarin red, AR... more Similarly to alizarin molecules, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonate (alizarin red, AR), chelates TiO 2 nanoparticles through the catechol moiety, and shifts the absorption threshold of the semiconductor to the visible region. The photoinduced reactivity of the coupled system AR@TiO 2 was investigated through quantum yields determinations in nonscattering sols of TiO 2 modified nanoparticles. In contrast with the behavior observed in TiO 2 microparticulated systems, the chemisorbed ligand has a high stability under aerated visible light irradiation. The quantum yield for alizarin red oxidation Φ -AR ) 4 × 10 -4 correlates with the negligible efficiency for oxygen reduction in the constrained environment of the smaller particles. Conversely, reduction of Cr(VI) to Cr(V) in the coupled AR@TiO 2 system, confirmed by electron paramagnetic resonance spectroscopy, utilizes a high fraction of the photogenerated electrons and induces the degradation of the complex. Quantum efficiencies for chromium(VI) disappearance, Φ -Cr(VI) , approaches 37% at [Cr(VI)] 0 ) 200 µM. The interactions between Cr(VI)/AR and Cr(VI)/TiO 2 are analyzed in detail. Spectroscopic evidence is presented for the first time that Cr(VI) forms a charge-transfer complex with TiO 2 nanoparticles that could be excited by visible light (λ e 440 nm). The environmental implications of the above findings are briefly discussed.

The Journal of Physical Chemistry Letters, 2013

The authors declare no competing financial interest. ■ ACKNOWLEDGMENTS O.R. acknowledges DGA (Fra... more The authors declare no competing financial interest. ■ ACKNOWLEDGMENTS O.R. acknowledges DGA (France) for financial support under contract 2010.60.095. V.N.M. thanks CONICET for a doctoral fellowship and ANPCyT (Argentina) projects PICT-

Environmental Science & Technology, 2012

Heterogeneous photocatalytic reduction of As(V) and As(III) at different concentrations over TiO ... more Heterogeneous photocatalytic reduction of As(V) and As(III) at different concentrations over TiO 2 under UV light in deoxygenated aqueous suspensions is described. For the first time, As(0) was unambiguously identified together with arsine (AsH 3 ) as reaction products. As(V) reduction requires the presence of an electron donor (methanol in the present case) and takes place through the hydroxymethyl radical formed from methanol oxidation by holes or hydroxyl radicals. On the contrary, As(III) reduction takes place through direct reduction by the TiO 2 -conduction band electrons. Detailed mechanisms for the photocatalytic processes are proposed. Although reduction to solid As(0) is convenient for purposes of As removal from water as a deposit on TiO 2 , attention must be paid to formation of AsH 3 , one of the most toxic forms of As, and strategies for AsH 3 treatment should be considered.

Numerous articles have reported the occurrence of arsenic in drinking water in Argentina, and the... more Numerous articles have reported the occurrence of arsenic in drinking water in Argentina, and the resulting health effects in severely affected regions of the country. . J. Environ. Res. Public Health 2015, 12 5466 Arsenic in drinking water in Argentina is largely naturally occurring due to elevated background content of the metalloid in volcanic sediments, although, in some regions, mining can contribute. While the origin of arsenic release has been discussed extensively, the problem of drinking water contamination has not yet been solved. One key step in progress towards mitigation of problems related with the consumption of As-containing water is the availability of simple detection tools. A chemical test kit and the ARSOlux biosensor were evaluated as simple analytical tools for field measurements of arsenic in the groundwater of Rafaela (Santa Fe, Argentina), and the results were compared with ICP-MS and HPLC-ICP-MS measurements. A survey of the groundwater chemistry was performed to evaluate possible interferences with the field tests. The results showed that the ARSOlux biosensor performed better than the chemical field test, that the predominant species of arsenic in the study area was arsenate and that arsenic concentration in the studied samples had a positive correlation with fluoride and vanadium, and a negative one with calcium and iron.

The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which... more The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which ethyl or methyl 2,3,5,6-tetra-O-benzoyl-o-giuconate (5 and 6) crystallized after treatment with ethanol or methanol, respectively. These esters *Research Member of the ConseJo National de Investigaclones Clentlficas y T&ucas Carbohyd. Res., 14 (1970) 103-107 1. 0. DFFiRRAR I, R. M. DE LED-, B. MATSUJ3JR0, M. I. LITTER

Applied Catalysis B: Environmental, 2011

In this work, the photocatalytic activity and the kinetic behavior of anatase TiO 2 films deposit... more In this work, the photocatalytic activity and the kinetic behavior of anatase TiO 2 films deposited by cathodic arc (CA films) on glass substrates are reported and compared with those of TiO 2 Degussa P-25 films obtained by dip-coating immersion (DC films). The mass density of films, determined by X-ray reflectometry was 20% lower for DC films compared with CA films, indicating a higher porosity of DC samples. The activity was evaluated from the efficiency to reduce Cr(VI) in the presence of EDTA. Although the response of CA films resulted lower compared with that of P-25 films of the same TiO 2 content (e.g. 90% vs. 50% Cr(VI) reduction after 180 min irradiation for samples with 0.03 mg cm −2 of TiO 2 ), a fact associated to the lower porosity, adhesion properties of the new materials were much better. CA film photoactivity improved by increasing the coating thickness; after 180 min, a sample with 0.03 mg cm −2 of TiO 2 presented 50% of Cr(VI) reduction vs. 80% for a sample with 0.28 mg cm −2 . These photocatalysts, whose preparation is simple and affordable, are very promising to be used as immobilized materials in photoreactors for the treatment of pollutants in gaseous and aqueous systems.

Procedia Materials Science, 2015

The aim of this work is to obtain porous titanium dioxide with good efficiency for photocatalytic... more The aim of this work is to obtain porous titanium dioxide with good efficiency for photocatalytic environmental applications. TiO 2 coatings were obtained by anodic spark deposition, at constant applied potential (150 V), using a platinum cathode and 0.5 M sulfuric acid as electrolyte. Samples of titanium Grade 2 were used as substrate, metallographically prepared until 1 μm diamond surface finishing. The variables of the process were temperature (25 and 40 °C) and anodization time (5 and 10 min). Samples obtained at 40 °C showed a higher current density than those obtained at 25 °C and the potential reached by these samples was lower than those obtained at 25 °C. These results are attributed to an increased electrolyte conductivity. Optical microscopy images of the oxides obtained at 40 ºC showed heterogeneity in color, indicating a non-uniform oxide thickness. This coincides with the images obtained by scanning electron microscopy that revealed "valleys" where the material did not present porosity. On the other hand, the oxides obtained at 25 °C showed a complete homogeneous porous structure. The average pore diameter was reduced with the increased oxidation time and temperature of the electrolyte. An increase of the crystalline anatase phase was observed with an increase of the anodization time; besides, rutile formation was observed, probably due to the final potential achieved by the samples.

Journal of Photochemistry and Photobiology A: Chemistry, 2002

In the present work, three commercially available TiO 2 -catalysts, namely Degussa P25, Sachtlebe... more In the present work, three commercially available TiO 2 -catalysts, namely Degussa P25, Sachtleben Hombikat UV100 and Millennium TiONA PC50, were platinised by a photochemical impregnation method in two ratios of platinum deposits (0.5 and 1 wt.%). The physical characterisation of the new synthesised catalysts was carried out by measurements of the BET-surface area, the light absorption properties and the adsorption of the model compounds. The photocatalytic activities of these samples were determined using three different model compounds: EDTA, 4-chlorophenol (4-CP), and dichloroacetic acid (DCA). While in the case of EDTA its disappearance was studied, total mineralisation was measured for 4-CP and DCA. In all cases, the photocatalytical activity was found to increase with rising amounts of Pt, e.g., the photonic efficiency for DCA degradation increased from 12.2% for pure Hombikat UV100 to 32.1% for Hombikat UV100/0.5 wt.% Pt and to 42.7% for Hombikat UV100/1 wt.% Pt. Promising results were also achieved for the total mineralisation of 4-CP. The photonic efficiency rised from 0.82% using unmodified PC50 to 1.14% with PC50/0.5 wt.% Pt (zero-order kinetics assumed in all cases). Similar results were obtained with the other new synthesised catalyst samples and for the model compound EDTA. No immediate relationship between the photocatalytic activity of the catalyst samples and their physical properties (surface area, adsorption of pollutants, absorption of light) could be observed.

Applied Catalysis A: General, 1999

Samples of iron-doped titania containing different amounts of Fe (0.5–5 wt%) prepared from TiCl 4... more Samples of iron-doped titania containing different amounts of Fe (0.5–5 wt%) prepared from TiCl 4 and Fe(III) acetylacetonate by a sol–gel method were tested as photocatalysts under near-UV irradiation for EDTA oxidation and for Cr(VI) reduction. Their efficiency has been ...

Journal of Photochemistry and Photobiology A: Chemistry, 2002

Two commercial samples, namely Degussa P-25 and Sachtleben Hombikat UV 100, and platinized modifi... more Two commercial samples, namely Degussa P-25 and Sachtleben Hombikat UV 100, and platinized modifications of these samples have been tested comparatively as photocatalysts for EDTA oxidation and for Cr(VI) reduction in the absence and in the presence of EDTA. Platinized photocatalysts were prepared by photoimpregnation of H 2 PtCl 6 on TiO 2 by prolonged irradiation in the presence of methanol. Only slight differences in efficiency were found between both pure commercial forms, except for the Cr(VI) reduction in the presence of EDTA, where Hombikat UV 100 samples were more active. Platinized Hombikat UV 100 was found to be less active for Cr(VI) reduction in water. The concentration of dissolved molecular oxygen was crucial for EDTA oxidation and had no influence on Cr(VI) reduction. From kinetic profiles, initial photonic efficiencies (ζ ) and conversion degrees have been calculated. Platinization did not improve Cr(VI) reduction but increased the initial photonic efficiency for EDTA oxidation. However, after prolonged irradiation, the conversion of EDTA was lower employing platinized samples instead of pure samples. The effect of platinum on titania was analyzed on the basis of proposed mechanisms.

Water science and technology : a journal of the International Association on Water Pollution Research, 2004

In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes ... more In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes has been performed: a) a homogeneous system with Fe(III)-NTA (1:1 complex), b) a TiO2/Fe(III)-NTA heterogeneous system. In both cases, NTA appears to play a positive role in the photochemical reaction. In the homogeneous system, the iron salt is the only absorbing species and is proved to be able to photoinduce 4-CP degradation ([4-CP] = 0.1-0.2 mM, [FeNTA] = 0.3-0.9 mM, pH 4, lambda = 365 nm). The progress of the reaction was positively affected by the FeNTA concentration, and the reaction kept going even after the total disappearance of FeNTA. However, 4-CP complete degradation requires the presence of oxygen, otherwise the reaction stops. In the heterogeneous system ([4-CP] = 2.0 mM, [FeNTA] = 1.0-2.0 mM, [TiO2] = 0.1 and 1.0 g L(-1), pH 3, lambda = 300-400 nm), an important effect of the complex on the degradation extent and on the initial reaction rate can be seen, which overcomes t...

Photochemical & Photobiological Sciences, 2010

Chromium(VI) reduction photoinduced by iron(III) nitrilotriacetate (FeNTA) was investigated under... more Chromium(VI) reduction photoinduced by iron(III) nitrilotriacetate (FeNTA) was investigated under monochromatic excitation. 313 nm was used as the irradiation wavelength in order to minimize the absorption of the light by chromium(VI): 91% of the photons were absorbed by FeNTA at pH = 7.0. Quantum yields of FeNTA and chromium(VI) disappearance and iron(II) formation were measured at pH 2.0, 4.0 and 7.0. In all the cases, chromium(VI) reduction follows first order kinetics with maximum efficiency at pH 2.0. The observed rate constant is proportional to FeNTA concentrations up to a maximum of 6.0 ¥ 10 -4 mol L -1 . The effect of oxygen was also investigated. If there is no large pH effect and no effect of oxygen on the quantum yields of chromium(VI) and FeNTA disappearance, the pH strongly influences the nature of the reduced chromium species. At pH 2.0, only chromium(III)was detected, whereas at pH 4.0 and 7.0 no chromium(III) resulting from chromium(VI) reduction was observed. Chromium(V) is supposed to be formed and stabilized by the chelating groups of NTA or NTA photoproducts.

The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which... more The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which ethyl or methyl 2,3,5,6-tetra-O-benzoyl-o-giuconate (5 and 6) crystallized after treatment with ethanol or methanol, respectively. These esters *Research Member of the ConseJo National de Investigaclones Clentlficas y T&ucas Carbohyd. Res., 14 (1970) 103-107 1. 0. DFFiRRAR I, R. M. DE LED-, B. MATSUJ3JR0, M. I. LITTER

Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2006

Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste tr... more Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, heterogeneous photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and/or the overall efficiency. This review addresses the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents. These combinations increase the photoprocess efficiency by decreasing the reaction time in respect to the separated operations or they decrease the cost in respect of heterogeneous photocatalysis alone, generally in terms of light energy. Depending on the operation coupled with heterogeneous photocatalysis, two categories of combinations exist. When the coupling is with ultrasonic irradiation, photo-Fenton reaction, ozonation, or electrochemical treatment, the combination affects the photocatalytic mechanisms thus improving the efficiency of the photocatalytic process. When the coupling is with biological treatment, membrane reactor, membrane photoreactor, or physical adsorption, the combination does not affect the photocatalytic mechanisms but it improves the efficiency of the overall process. The choice of the coupling is related to the type of wastewater to be treated. A synergistic effect, giving rise to an improvement of the efficiency of the photocatalytic process, has been reported in the literature for many cases.

h i g h l i g h t s UV-vis photocatalytic reduction of uranyl is revisited. Systems with nitrate ... more h i g h l i g h t s UV-vis photocatalytic reduction of uranyl is revisited. Systems with nitrate and perchlorate are the best for U(VI) removal. Acetate plays a negative role in U(VI) removal. In the absence and presence of 2-propanol main reduction mechanism is e CB À attack.

Ecotoxicology and Environmental Safety, 2015

Toxicity of a Cr(VI) solution before and after treatment by TiO2 heterogeneous photocatalysis (HP... more Toxicity of a Cr(VI) solution before and after treatment by TiO2 heterogeneous photocatalysis (HP) was performed with AMPHITOX bioassay. Changes in toxicity on Rhinella arenarum larvae for 10-d were monitored after exposure to an untreated Cr(VI) solution and to the same solution after HP treatment. The HP treatment of a 41.60mgL(-1) Cr(VI) solution reduced to 37.5% the concentration of the metal ion. A 10-fold reduction in toxicity at acute exposure (72h) and 150-fold reduction in toxicity after 240h was found. Further, the LOEC value increased from 0.001% for the untreated solution to 0.153% after HP treatment. Moreover, the safe concentration in untreated solution corresponded to 0.0001% sample, and it was 0.01% after the treatment, i.e., 100 times higher. A saving of water of about 100,000L per L of effluent would be possible through dilution to allow safer concentrations for discharge; the saving would reach the highest value (1,000,000L per L) at 240h. Sub-lethal effects were completely absent in larvae exposed to the treated solution. The AMPHITOX test allowed to detect chronic effects at low Cr concentrations, i.e. at environmentally relevant levels.

Science of The Total Environment, 2015

Four million people in Argentina are exposed to arsenic contamination from drinking waters of sev... more Four million people in Argentina are exposed to arsenic contamination from drinking waters of several center-northern provinces. A systematic review to examine the geographical distribution of arsenic-related diseases in Argentina was conducted, searching electronic databases and gray literature up to November 2013. Key informants were also contacted. Of the 430 references identified, 47 (mostly cross-sectional and ecological designs) referred to arsenic concentration in water and its relationship with the incidence and mortality of cancer, dermatological diseases and genetic disorders. A high percentage of the water samples had arsenic concentrations above the WHO threshold value of 10μg/L, especially in the province of Buenos Aires. The median prevalence of arsenicosis was 2.6% in exposed areas. The proportion of skin cancer in patients with arsenicosis reached 88% in case-series from the Buenos Aires province. We found higher incidence rate ratios per 100μg/L increment in inorganic arsenic concentration for colorectal, lung, breast, prostate and skin cancer, for both genders. Liver and skin cancer mortality risk ratios were higher in regions with medium/high concentrations than in those with low concentrations. The relative risk of mortality by skin cancer associated to arsenic exposure in the province of Buenos Aires ranged from 2.5 to 5.2. In the north of this province, high levels of arsenic in drinking water were reported; however, removal interventions were scarcely documented. Arsenic contamination in Argentina is associated with an increased risk of serious chronic diseases, including cancer, showing the need for adequate and timely actions.

The Journal of Physical Chemistry C, 2008

Similarly to alizarin molecules, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonate (alizarin red, AR... more Similarly to alizarin molecules, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonate (alizarin red, AR), chelates TiO 2 nanoparticles through the catechol moiety, and shifts the absorption threshold of the semiconductor to the visible region. The photoinduced reactivity of the coupled system AR@TiO 2 was investigated through quantum yields determinations in nonscattering sols of TiO 2 modified nanoparticles. In contrast with the behavior observed in TiO 2 microparticulated systems, the chemisorbed ligand has a high stability under aerated visible light irradiation. The quantum yield for alizarin red oxidation Φ -AR ) 4 × 10 -4 correlates with the negligible efficiency for oxygen reduction in the constrained environment of the smaller particles. Conversely, reduction of Cr(VI) to Cr(V) in the coupled AR@TiO 2 system, confirmed by electron paramagnetic resonance spectroscopy, utilizes a high fraction of the photogenerated electrons and induces the degradation of the complex. Quantum efficiencies for chromium(VI) disappearance, Φ -Cr(VI) , approaches 37% at [Cr(VI)] 0 ) 200 µM. The interactions between Cr(VI)/AR and Cr(VI)/TiO 2 are analyzed in detail. Spectroscopic evidence is presented for the first time that Cr(VI) forms a charge-transfer complex with TiO 2 nanoparticles that could be excited by visible light (λ e 440 nm). The environmental implications of the above findings are briefly discussed.

The Journal of Physical Chemistry Letters, 2013

The authors declare no competing financial interest. ■ ACKNOWLEDGMENTS O.R. acknowledges DGA (Fra... more The authors declare no competing financial interest. ■ ACKNOWLEDGMENTS O.R. acknowledges DGA (France) for financial support under contract 2010.60.095. V.N.M. thanks CONICET for a doctoral fellowship and ANPCyT (Argentina) projects PICT-

Environmental Science & Technology, 2012

Heterogeneous photocatalytic reduction of As(V) and As(III) at different concentrations over TiO ... more Heterogeneous photocatalytic reduction of As(V) and As(III) at different concentrations over TiO 2 under UV light in deoxygenated aqueous suspensions is described. For the first time, As(0) was unambiguously identified together with arsine (AsH 3 ) as reaction products. As(V) reduction requires the presence of an electron donor (methanol in the present case) and takes place through the hydroxymethyl radical formed from methanol oxidation by holes or hydroxyl radicals. On the contrary, As(III) reduction takes place through direct reduction by the TiO 2 -conduction band electrons. Detailed mechanisms for the photocatalytic processes are proposed. Although reduction to solid As(0) is convenient for purposes of As removal from water as a deposit on TiO 2 , attention must be paid to formation of AsH 3 , one of the most toxic forms of As, and strategies for AsH 3 treatment should be considered.

Numerous articles have reported the occurrence of arsenic in drinking water in Argentina, and the... more Numerous articles have reported the occurrence of arsenic in drinking water in Argentina, and the resulting health effects in severely affected regions of the country. . J. Environ. Res. Public Health 2015, 12 5466 Arsenic in drinking water in Argentina is largely naturally occurring due to elevated background content of the metalloid in volcanic sediments, although, in some regions, mining can contribute. While the origin of arsenic release has been discussed extensively, the problem of drinking water contamination has not yet been solved. One key step in progress towards mitigation of problems related with the consumption of As-containing water is the availability of simple detection tools. A chemical test kit and the ARSOlux biosensor were evaluated as simple analytical tools for field measurements of arsenic in the groundwater of Rafaela (Santa Fe, Argentina), and the results were compared with ICP-MS and HPLC-ICP-MS measurements. A survey of the groundwater chemistry was performed to evaluate possible interferences with the field tests. The results showed that the ARSOlux biosensor performed better than the chemical field test, that the predominant species of arsenic in the study area was arsenate and that arsenic concentration in the studied samples had a positive correlation with fluoride and vanadium, and a negative one with calcium and iron.

The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which... more The reactlon of D-gluconamlde with benzoyl chloride and pyrldme gave a complex mixture from which ethyl or methyl 2,3,5,6-tetra-O-benzoyl-o-giuconate (5 and 6) crystallized after treatment with ethanol or methanol, respectively. These esters *Research Member of the ConseJo National de Investigaclones Clentlficas y T&ucas Carbohyd. Res., 14 (1970) 103-107 1. 0. DFFiRRAR I, R. M. DE LED-, B. MATSUJ3JR0, M. I. LITTER

Applied Catalysis B: Environmental, 2011

In this work, the photocatalytic activity and the kinetic behavior of anatase TiO 2 films deposit... more In this work, the photocatalytic activity and the kinetic behavior of anatase TiO 2 films deposited by cathodic arc (CA films) on glass substrates are reported and compared with those of TiO 2 Degussa P-25 films obtained by dip-coating immersion (DC films). The mass density of films, determined by X-ray reflectometry was 20% lower for DC films compared with CA films, indicating a higher porosity of DC samples. The activity was evaluated from the efficiency to reduce Cr(VI) in the presence of EDTA. Although the response of CA films resulted lower compared with that of P-25 films of the same TiO 2 content (e.g. 90% vs. 50% Cr(VI) reduction after 180 min irradiation for samples with 0.03 mg cm −2 of TiO 2 ), a fact associated to the lower porosity, adhesion properties of the new materials were much better. CA film photoactivity improved by increasing the coating thickness; after 180 min, a sample with 0.03 mg cm −2 of TiO 2 presented 50% of Cr(VI) reduction vs. 80% for a sample with 0.28 mg cm −2 . These photocatalysts, whose preparation is simple and affordable, are very promising to be used as immobilized materials in photoreactors for the treatment of pollutants in gaseous and aqueous systems.

Plastic waste generation and management during industrial transformation and at post-consumer sta... more Plastic waste generation and management during industrial transformation and at post-consumer stage has been a problem of economic efficiency since the late 1940s [1,2]. More recently, sustainability considerations have gained widespread adoption not only in traditional industrial processes but specifically in 3D Printing (3DP) technologies [3]. Production and distribution considerations of functional 3DP devices as added value recycled products have recently been addressed [4].