Photocatalytic Synthesis of Hydrogen Peroxide from Molecular Oxygen and Water.

Hydrogen peroxide is a powerful and green oxidant that allows for the oxidation of a wide span of organic and inorganic substrates in liquid media under mild reaction conditions, and forms only molecular water and oxygen as end products. Hydrogen peroxide is therefore used in a wide range of applications, for which the well-documented and established anthraquinone autoxidation process is by far the dominating production method at the industrial scale. As this method is highly energy consuming and environmentally costly, the search for more sustainable synthesis methods is of high interest. To this end, the article reviews the basis and the recent development of the photocatalytic synthesis of hydrogen peroxide. Different oxygen reduction and water oxidation mechanisms are discussed, as well as several kinetic models, and the influence of the main key reaction parameters is itemized. A large range of photocatalytic materials is reviewed, with emphasis on titania-based photocatalysts and on high-prospect graphitic carbon nitride-based systems that take advantage of advanced bulk and surface synthetic approaches. Strategies for enhancing the performances of solar-driven photocatalysts are reported, and the search for new, alternative, photocatalytic materials is detailed. Finally, the promise of in situ photocatalytic synthesis of hydrogen peroxide for water treatment and organic synthesis is described, as well as its coupling with enzymes and the direct in situ synthesis of other technical peroxides.

Irradiance-Controlled Photoassisted Synthesis of Sub-Nanometre Sized Ruthenium Nanoparticles as Co-Catalyst for TiO2 in Photocatalytic Reactions.

Photoassisted synthesis is as a highly appealing green procedure for controlled decoration of semiconductor catalysts with co-catalyst nanoparticles, which can be carried out without the concourse of elevated temperatures, external chemical reducing agents or applied bias potential and in a simple slurry reactor. The aim of this study is to evaluate the control that such a photoassisted method can exert on the properties of ruthenium nanoparticles supported on TiO2 by means of the variation of the incident irradiance and hence of the photodeposition rate. For that purpose, different Ru/TiO2 systems with the same metal load have been prepared under varying irradiance and characterized by means of elemental analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of the so-obtained materials has been evaluated by using the degradation of formic acid in water under UV-A light. Particles with size around or below one nanometer were obtained, depending on the irradiance employed in the synthesis, with narrow size distribution and homogeneous dispersion over the titania support. The relation between neutral and positive oxidation states of ruthenium could also be controlled by the variation of the irradiance. The obtained photocatalytic activities for formic acid oxidation were in all cases higher than that of undecorated titania, with the sample obtained with the lowest irradiation giving rise to the highest oxidation rate. According to the catalysts characterization, photocatalytic activity is influenced by both Ru size and Ru0/Ruδ+ ratio.

Ti-Modified LaFeO3/ß-SiC Alveolar Foams as Immobilized Dual Catalysts with Combined Photo-Fenton and Photocatalytic Activity.

Ti-modified LaFeO3/ß-SiC alveolar foams were used as immobilized, highly robust dual catalysts with combined photocatalytic wet peroxide oxidation and photocatalytic activity under UV-A light. They were prepared by incipient wetness impregnation of a ß-SiC foam support, by implementing a sol-gel Pechini synthesis at the foam surface in the presence of dried amorphous sol-gel titania as a titanium source. The physicochemical and catalytic features suggest the stabilization at the foam surface of a substituted La1-xTixFeO3 catalyst analogous to its powdery counterpart. Taking 4-chlorophenol removal in water as a model reaction, its dual nature enables both high reaction rates and full total organic carbon (TOC) conversion because of a synergy effect, while its macroscopic structure overcomes the drawback of working with powdery catalysts. Further, it yields photonic efficiencies for degradation and mineralization of ca. 9.4 and 38%, respectively, that strongly outperform those obtained with a reference TiO2 P25/ß-SiC foam photocatalyst. The enhancement of the catalyst robustness upon Ti modification prevents any Fe leaching to the solution, and therefore, the optimized macroscopic foam catalyst with 10 wt % catalyst loading operates through pure heterogeneous surface reactions, without any activity loss during reusability test cycles.

Activity enhancement pathways in LaFeO3@TiO2 heterojunction photocatalysts for visible and solar light driven degradation of myclobutanil pesticide in water.

LaFeO3@TiO2 heterojunction composites with a core-shell porous structure and LaFeO3 contents in the 2.5-25 wt.% range have been synthesized via consecutive sol-gel syntheses and tested for the photocatalytic oxidation of the myclobutanil pesticide in water under solar light and pure visible light. Whatever the light spectrum, the kinetic rate constants for both myclobutanil degradation and TOC conversion exhibited a volcano-like profile with increasing the narrow band-gap (2.1 eV) LaFeO3 content, the optimum composite strongly overperforming both single phases, with full myclobutanil mineralization achieved in 240 min in the best case. The light spectrum influenced the optimum LaFeO3 content in the composite, being observed at 5 wt.% and 12.5 wt.% under solar and visible light, respectively. This has been attributed to the existence of different light-mediated reaction mechanisms. The optimum LaFeO3/TiO2 composite photocatalyst was active and stable after several runs under solar light with leached iron concentration below 0.1 mg/L in solution.

Body Mass Index as a Prognostic Factor in Liver Transplantation.

OBJECTIVE: Obesity is one of the main growing epidemics of the last century and is responsible for many deaths worldwide. The aim of this study is to analyze the impact of the body mass index (BMI) of the recipient on survival and morbidity after liver transplantation (LT). MATERIAL AND METHODS: We conducted a retrospective cohort study of all transplanted recipients in a third-level hospital between 2006 and 2018. The following donor variables were analyzed: age, sex, weight, BMI, cause of death. Additionally, the following recipient variables were analyzed: age, sex, weight, height, BMI, procedure indication. Finally, outcome variables were analyzed: postoperative complications, early mortality, graft loss, and overall survival. This study strictly complies with the Helsinki Congress and the Istanbul Declaration regarding donor source. RESULTS: We analyzed 825 of 837 LTs from January 2006 to December 2018. These were grouped by BMI categories: 271 (29%) normal, 322 (34.3%) overweight, and 228 (24.3%) obesity. The overall survival at 5 years was 83% in the normal group, 76% in the overweight group, and 71% in the obesity group. These differences were statistically significant (P = .027). The early mortality rate was 4.42% in the normal weight group, 6.5% in the overweight group, and 5.26% in the obesity group. No differences were found between groups in terms of postoperative complications: hemorrhagic, vascular, biliary, respiratory, hemodynamic, digestive, renal, neurologic, rebel ascites, and infections. No differences were found regarding the need for re-operation. CONCLUSIONS: In this study, overall survival in LT decreases as the BMI of recipient increases; but overweight and obesity do not constitute a risk factor for early morbidity and mortality in LT.

Coating-free TiO2@ß-SiC alveolar foams as a ready-to-use composite photocatalyst with tunable adsorption properties for water treatment.

Coating-free TiO2@ß-SiC photocatalytic composite foams gathered within a ready-to-use shell/core alveolar medium the photocatalytically active TiO2 phase and the ß-SiC foam structure were prepared via a multi-step shape memory synthesis (SMS) replica method. They were fabricated following a sequential two-step carburization approach, in which an external TiC skin was synthesized at the surface of a ß-SiC skeleton foam obtained from a pre-shaped polyurethane foam during a first carburization step. The adsorption behaviour of the shell/core TiO2@ß-SiC composite foams towards the Diuron pollutant in water was tuned by submitting the carbide foams to a final calcination treatment within the 550-700 °C temperature range. The controlled calcination step allowed (i) the selective oxidation of the TiC shell into a TiO2 crystallite shell owing to the ß-SiC resistance to oxidation and (ii) the amount of residual unreacted carbon in the foams to be tuned. The lower the calcination temperature, the more pronounced the adsorption profiles of the composites and the higher the Diuron amount removed by adsorption on the residual unreacted carbon. The ready-to-use TiO2@ß-SiC composite foams were active in the degradation of the Diuron pesticide, without any further post-synthesis immobilization or synthesis process at the foam surface. They displayed good reusability with test cycles and benefitted from an enhanced stability in terms of the titania release to water.

Ferrite Materials for Photoassisted Environmental and Solar Fuels Applications.

Ferrites are a large class of oxides containing Fe3+ and at least another metal cation that have been investigated for and applied to a wide variety of fields ranging from mature technologies like circuitry, permanent magnets, magnetic recording and microwave devices to the most recent developments in areas like bioimaging, gas sensing and photocatalysis. In the last respect, although ferrites have been less studied than other types of semiconductors, they present interesting properties such as visible light absorption, tuneable optoelectronic properties and high chemical and photochemical stability. The versatility of their chemical composition and of their crystallographic structure opened a playground for developing new catalysts with enhanced efficiency. This article reviews the recent development of the application of ferrites to photoassisted processes for environmental remediation and for the synthesis of solar fuels. Applications in the photocatalytic degradation of pollutants in water and air, photo-Fenton, and solar fuels production, via photocatalytic and photoelectrochemical water splitting and CO2 reduction, are reviewed paying special attention to the relationships between the physico-chemical characteristics of the ferrite materials and their photoactivated performance.

Evaluation of photoassisted treatments for norfloxacin removal in water using mesoporous Fe2O3-TiO2 materials.

We report the synthesis of mesoporous TiO2 and mesoporous Fe2O3-TiO2 catalysts by using a structure-directing-surfactant method, their characterization and their employment as photocatalysts for norfloxacin degradation in aqueous solution. The main findings show that in the presence of both O2 and H2O2, Fe-containing mesoporous titania (Fe2O3-TiO2), with iron percentages between 1 and 3 wt%, exhibited norfloxacin degradation rates more than 60% greater than otherwise identical mesoporous titania without iron. Furthermore, the activity of the mesoporous composite catalysts also exceeds that of titania when illuminated with 405 nm light-emitting diodes. Iron loading improved the photocatalytic activity for norfloxacin degradation with values of apparent reaction rate constants of 0.037 min-1 and 0.076 min-1 with 1 and 3 surface wt.% of iron, respectively. An optimum of activity was found with the 3 wt% Fe2O3-TiO2 catalyst. Under these conditions, 10 mg/L of norfloxacin is reacted essentially to completion and 90% of total organic carbon conversion was obtained within 120 min of reaction. This higher organic carbon conversion degree was reached due to the photo-oxidation of short-chain organic acids. The high activity of the as-synthesized mesoporous composites is attributed to the additional iron phase which led to the different reactions for H2O2 decomposition, but also due to the improvement in light absorbance. Finally, the activity of the most active catalyst was found to be stable over multiple sequential runs, which was related to a negligible amount of iron leaching (<0.1%) from these materials.

Intususcepción apendicular / Intussusception of the appendix

No disponible

Photoactive ZnO Materials for Solar Light-Induced CuxO-ZnO Catalyst Preparation.

In this work, the solar light-induced redox photoactivity of ZnO semiconductor material was used to prepare CuxO-ZnO composite catalysts at room temperature with a control of the chemical state of the copper oxide phase. Cu2(I)O-ZnO and Cu(II)O-ZnO composite catalysts were prepared by using Cu(acac)2 in tetrahydrofuran-water and Cu(NO3)2 in water as metallic precursor, respectively. Prior to the implementation of the photon-assisted synthesis method, the most efficient photoactive ZnO material was selected from among different ZnO materials prepared by the low temperature polyol and precipitation methods with carbonates and carbamates as precipitation agents. The photocatalytic degradation of the 4-chlorophenol compound in water under simulated solar light was taken as a model reaction. The ZnO support materials were characterized by X-ray diffraction (XRD), surface area and porosimetry measurements, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the synthesis method strongly influenced their photoactivity in terms of 4-chlorophenol degradation and of total organic carbon removal. The most photoactive ZnO material was prepared by precipitation with carbonates and calcined at 300 °C, benefitting from a high specific surface area and a small mean crystallite size for achieving a complete 4-chlorophenol mineralization within 70 min of reaction, with minimum Zn2+ released to the solution. Besides thermal catalysis applications, this work has opened a new route for the facile synthesis of Cu2O-ZnO heterojunction photocatalysts that could take place under solar light of the heterojunction built between the p-type semi-conductor Cu2O with direct visible light band gap and the ZnO semiconductor phase.

Improving the Fenton process by visible LED irradiation.

The effect of irradiation with visible light-emitting diode (LED) light on the efficiency of Fenton oxidation is investigated using phenol as the target compound (100 mg/L). The H2O2 dose and temperature are tested as operating variables with the aim of minimizing consumption of the reagents. At 50 °C, 10 mg/L Fe2+, and 60 % of the stoichiometric H2O2 amount, phenol was completely oxidized into CO2, H2O, and short chain organic acids, with oxalic acid completely degraded. Up to 95 % mineralization was achieved. This high efficiency can be attributed to the effect of LED radiation on the quinones/Fe2+/Fe3+/H2O2 cycle, which significantly increases the reaction rate, as well as on the photodecomposition of the iron complexes formed along the oxidation process, which also enhanced mineralization.

Effect of water composition on the photocatalytic removal of pesticides with different TiO2 catalysts.

The objective of this work is double-firstly to explore the photocatalytic efficiency of five different commercial TiO2 catalysts in the photodegradation of a mixture of pesticides classified by the EU as priority pollutants and secondly to analyze the correlation between their physicochemical properties and the inhibition of the studied photocatalytic process when natural water was employed. Photocatalytic efficiencies when ultrapure water was used seem to point out that surface area was not a prerequisite for the photodegradation of the selected mixture of pesticides. On the other hand, significant differences in total organic carbon (TOC) conversions were obtained with the two studied water compositions. On one side, Evonik materials appear to be mostly inhibited when natural water was employed, whereas on the other, it should be remarked that anatase Sigma-Aldrich (SA) and, particularly, Hombikat UV100 (HBK) materials presented a very limited photo-efficiency inhibition or even a higher initial rate of TOC removal when a natural water matrix was used, probably due to their specific surface properties (PZC, S BET). Therefore, heterogeneous photocatalysis has proved to be a promising technology for the degradation of the selected mixture of pesticides where the final photo-efficiency of the five commercial titania catalysts studied here responds to a complex balance between its surface and structural properties.

[Promoter hypermethylation gene patterns in gynecological tumors]. / Patrones de hipermetilación génica en tumores ginecológicos.

BACKGROUND AND OBJECTIVE: Gene silencing mediated by the aberrant methylation of the promoter region of DNA is involved in the inactivation of genes implicated in various metabolic pathways. Such a gene hypermethylation has become a useful molecular marker for the diagnosis, treatment and follow-up of cancer patients. Our objective is to analyze the patterns of gene hypermethylation in patients with gynecological tumors. PATIENTS AND METHODS: We selected 115 patients with gynecological cancers: 22 ovarian; 13 endometrial, 11 cervical-uterine and 69 breast cancers. By testing methylation-specific PCR, we studied the methylation status of genes CDNK2A (p16), APC1A, FHIT, CDH1 and hMLH1. RESULTS: The frequencies of gene methylation in genes p16, APC1A, FHIT, hMLH1 and CDH1 were 29.2%, 34%, 60.4%, 10.9% and 79.8%, respectively. 70% of cases showed at least two methylated genes, which means a rate of methylation >0.4. The lowest frequency of methylation was seen in ovarian cancer, while the highest one was observed in endometrial cancer. CONCLUSIONS: The results indicate that the aberrant methylation of the promoter region is an important event in carcinogenesis of gynecological tumors and that the pattern of gene methylation is associated with the nature of the tumor. These particular characteristics can deliver relevant information on the major metabolic pathways altered in each tumor type. In addition to complementary studies (ie, loss of expression and/or function), this represents a clinical tool for the proper management of the disease.

Patrones de hipermetilación génica en tumores ginecológicos / Promoter Hypermethylation gene patterns in gynecological tumors

Fundamento y objetivo: El silenciamiento génico mediado por la metilación aberrante de la región promotora del ácido desoxirribonucleico está implicado en la inactivación de genes involucrados en diversas vías metabólicas y se ha constituido en un marcador molecular útil en el diagnóstico, tratamiento y seguimiento de sujetos oncológicos. El objetivo de este trabajo es analizar los patrones de hipermetilación génica en mujeres con tumores ginecológicos. Sujetos y método: Se seleccionaron 115 mujeres con cánceres ginecológicos: 22 mujeres con cáncer de ovario (CO), 13 mujeres con cáncer de endometrio (CE), 11 mujeres con cáncer de cuello uterino y 69 mujeres con cáncer de mama. Mediante prueba de metilación específica por reacción en cadena de la polimerasa, se estudió el estado de metilación de los genes CDNK2A (p16), APC1A, FHIT, CDH1 y hMLH1.ResultadosLas frecuencias de metilación génica para los genes CDNK2A (p16), APC1A, FHIT, CDH1 y hMLH1 fueron del 29,2; 34; 60,4; 10,9, y 79,8%, respectivamente. El 70% de los casos presentó al menos 2 genes metilados, es decir, un índice de metilación superior a 0,4. La frecuencia de metilación más baja se observó en el CO, mientras que la frecuencia de metilación más alta se presentó en el CE. Conclusiones: Los resultados indican que la metilación aberrante de la región promotora es un acontecimiento importante en la carcinogénesis de los tumores ginecológicos y que el patrón de metilación génica se asocia a la naturaleza tumoral. Estas características particulares pueden entregar información relevante acerca de las principales vías metabólicas alteradas en cada tipo tumoral, información que sumada a estudios complementarios de pérdida de expresión o de función representa una herramienta clínica para el tratamiento adecuado de la enfermedad (AU)

Background and objective: Gene silencing mediated by the aberrant methylation of the promoter region of DNA is involved in the inactivation of genes implicated in various metabolic pathways. Such a gene hypermethylation has become a useful molecular marker for the diagnosis, treatment and follow-up of cancer patients. Our objective is to analyze the patterns of gene hypermethylation in patients with gynecological tumors. Patients and methods: We selected 115 patients with gynecological cancers: 22 ovarian; 13 endometrial, 11 cervical-uterine and 69 breast cancers. By testing methylation-specific PCR, we studied the methylation status of genes CDNK2A (p16), APC1A, FHIT, CDH1 and hMLH1.ResultsThe frequencies of gene methylation in genes p16, APC1A, FHIT, hMLH1 and CDH1 were 29.2%, 34%, 60.4%, 10.9% and 79.8%, respectively. 70% of cases showed at least two methylated genes, which means a rate of methylation >0.4. The lowest frequency of methylation was seen in ovarian cancer, while the highest one was observed in endometrial cancer. Conclusions: The results indicate that the aberrant methylation of the promoter region is an important event in carcinogenesis of gynecological tumors and that the pattern of gene methylation is associated with the nature of the tumor. These particular characteristics can deliver relevant information on the major metabolic pathways altered in each tumor type. In addition to complementary studies (ie, loss of expression and/or function), this represents a clinical tool for the proper management of the disease (AU)