Light-driven urea oxidation for a wearable artificial kidney

For the development of a wearable artificial kidney (WAK) that uses a small dialysate volume that is continuously regenerated, it is essential that urea, one of the main uremic retention solutes, is removed. Despite advances in sorbent technology or electro-oxidation no safe, efficient and selective method for urea removal has been reported that allows miniaturization of the artificial kidney to wearable proportions. Here we have developed a flow cell for light-driven, photo-electrocatalytic (PEC) urea removal for use in a WAK. We use a photo-active material (hematite) coated with a catalyst (NiOOH) as working electrode for selective urea oxidation and a silver-chloride (AgCl) cathode. The use of the AgCl counter electrodes eliminates the need for an external bias voltage, and allows operation under light illumination only. Using LED illumination (460 nm) we show that urea is selectively oxidized over chloride. N2 formation is confirmed by gas-phase analysis of the headspace of the sample vial, using mass spectrometry. Other nitrogen containing products include nitrite but importantly ammonia and nitrate are not detected. Using the PEC concept a urea removal rate of 2.5 μmol/cm2h (or 0.15 mg/cm2h) has been achieved. Extrapolating our results to an upscaled system, a surface area of 0.5 m2 would enable efficient removal of the daily produced amount of urea (∼300 mmol) urea within 24 h, when driven by LED illumination only

Bypass and hyperbole in soil science:A perspective from the next generation of soil scientists

International audienceWe, the co‐authors of this letter, are an international group of soil scientists at early career stages, from PhD students to postdoctoral researchers, lecturers, and research fellows with permanent positions. Here, we present our collective musings on soil research challenges and opportunities and, in particular, the points raised by Philippe Baveye (Baveye, 2020a, 2020b) and Johan Bouma (Bouma, 2020) on bypass and hyperbole in soil science. Raising awareness about these issues is a first and necessary step. To this end, we would like to thank Philippe Baveye and Johan Bouma for initiating this debate.......

La política educativa de Antonio Gil de Zárate

1) Comprobar si la teoría de Antonio Gil de Zárate sobre la función del Estado es competente o no. 2) Constatar si la libertad de enseñanza: -es una piedra de toque de la verdadera democracia; -es uno de los principios fundamentales de toda política educativa. 3) Hacer ver que sin educación familiar no es posible: -la educación en la libertad ni la libertad de enseñanza; -la formación personal y que sin ésta será imposible todo cambio social. 4) Buscar otra solución más justa e igualatoria a la elección de las familias, cualesquiera que sea su posición, del tipo de educación y escuela que prefieren y comprobar si la educación es una labor cooperativa y dentro de la cual los agentes principales y naturales son la familia y el Estado. Ideas centralistas y monopolizadoras de Antonio Gil de Zárate, en torno a estos temas: derechos de la familia, función del Estado, familia-Estado, la familia como institución educativa, y la libertad de enseñanza. Estudio crítico de los principios político-pedagógicos de Antonio Gil de Zárate basándonos fundamentalmente en su obra 'La Instrucción Púlica en España', que consta de tres volúmenes y es la única fuente de su pensamiento político pedagógico. Los derechos de la libertad de enseñanza se fundamentan en los derechos de la familia, pero no en el temor de que el Estado llegue a esclavizar el pensamiento o dar la educación torcida; al Estado no le corresponde este derecho a educar, ni a la persona el de ser educada, como no sea de acuerdo con las convicciones de la familia y eso sí, ordenadas al bien común. La educación familiar está en la base de la educación moral. Antonio Gil de Zárate no tiene razón al decir que la familia no puede educar porque dejaría al Estado un miembro inútil y un funesto legado. Es partidario de una libertad, pero controlada.CataluñaES

Water-dispersible clay in bare fallow soils after 80 years of continuous fertilizer addition

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The Valborraz tungsten mine: Description of a potential source of arsenic pollution

Soil contamination levels were studied in the land affected by an abandoned tungsten mine in Valdeorras (NW Spain). The mine worked mainly in the first half of the twentieth century, and it was definitely closed by 1953. Soil samples were taken in thirteen points within the mine (including both natural soils and soils developed over mine wastes), and in two natural soils close to the mine area. Total heavy metals (Fe, Zn, Ni and Cu) and As were analyzed by X-ray fluorescence in sieved (1000 mg kg-1) were found in all the samples of the mine area, whereas for the heavy metals analyzed no abnormally high concentrations were observed. Although high As background levels are common in soils developed over slates in the region, the concentrations found for the natural soils within the mine were too high to have a geological origin, and they are probably due to contamination from the close mine dumps. The As concentrations in the mine soils were higher than in the natural soils, ranging from 0.5-1% approximately. The highest As concentrations (near 4%) were found in iron oxyhydroxide deposits, which precipitate directly from water in some places in the area. This high As concentrations represent a certain threat to environmental health which has not been quantified yet. Although additional research is needed to determine the potential ecological and human health risks associated with the mine, our results suggest that this location could act as a dangerous As source

Light-driven urea oxidation for a wearable artificial kidney

For the development of a wearable artificial kidney (WAK) that uses a small dialysate volume that is continuously regenerated, it is essential that urea, one of the main uremic retention solutes, is removed. Despite advances in sorbent technology or electro-oxidation no safe, efficient and selective method for urea removal has been reported that allows miniaturization of the artificial kidney to wearable proportions. Here we have developed a flow cell for light-driven, photo-electrocatalytic (PEC) urea removal for use in a WAK. We use a photo-active material (hematite) coated with a catalyst (NiOOH) as working electrode for selective urea oxidation and a silver-chloride (AgCl) cathode. The use of the AgCl counter electrodes eliminates the need for an external bias voltage, and allows operation under light illumination only. Using LED illumination (460 nm) we show that urea is selectively oxidized over chloride. N2 formation is confirmed by gas-phase analysis of the headspace of the sample vial, using mass spectrometry. Other nitrogen containing products include nitrite but importantly ammonia and nitrate are not detected. Using the PEC concept a urea removal rate of 2.5 μmol/cm2h (or 0.15 mg/cm2h) has been achieved. Extrapolating our results to an upscaled system, a surface area of 0.5 m2 would enable efficient removal of the daily produced amount of urea (∼300 mmol) urea within 24 h, when driven by LED illumination only

Mineralogy and modulus of rupture of roofing slate: Applications in the prospection and quarrying of slate deposits

The European norm UNE 12326 for roofing slate defines the mechanical properties of a slate tile through the Bending Strength test, which defines the modulus of rupture (MoR) of the tile. This MoR is related to the durability of the slate, and is one of its main commercial quality properties. During the prospection task previous to open a new slate quarry, it is crucial to define the MoR. The Bending Strength test needs proper slate tiles and a flexion press. To supply these slate tiles it is frequently necessary to open experimental quarry fronts, which are very expensive, and do not guarantee the viability of the quarry. Therefore, a method which could reduce the costs and time for the mechanical characterization would be very useful. In this work we have tried to relate the MoR to the mineralogical and petrographic characteristics of slate, using the Petrographic Examination test, also part of UNE 12326. This test contemplates the finding of a numerical index called Mica Stacking Index (MSI) which quantifies the mica layers fabric. We collected fifteen samples of roofing slates from the Northwest of the Iberian Peninsula and we studied them by using the Bending Strength and Petrographic Examination tests, plus mineralogical quantification using X-ray diffraction and measure of the illite crystallinity (Kubler Index) to determine the metamorphic grade. We have found a strong positive correlation between MoR values and MSI, and a negative correlation between MoR and Mica percentages. These correlations may be used to deduce the MoR, reducing costs during the exploitation labours in roofing slate mining, and also can be used in the quality controls on a working slate quarry

La collection historique d’échantillons de sols de l’essai patrimonial des ‘42 parcelles’ (INRAE, Versailles) : une machine à remonter le temps...

International audienceFollowing three previous papers (van Oort et al., 2016, 2017, 2020) dealing with current soil characteristics and geochemical budgets in surface horizons, as well as the impacts of fertilization in subsurface horizons in soils of INRAE’s long term bare fallow experiment (the 42-plots trial), we now present some chronological aspects of soil evolution at the soil’s surface since 1928. For that, we analyzed several series of about 15 samples from the historical sample archive for 10 representative treatments: fertilizers with acidifying effects (ammonium sulphate, ammonium phosphate), fertilizers with dispersive effects (sodium nitrate, sylvinite, and potassium chloride), superphosphate, amendments with alkaline effects (basic slag, calcium carbonate), horse manure, as well as two reference plots, without inputs. We examined temporal evolutions of: i) edaphic parameters such as organic carbon and clay contents, pH, CEC and exchangeable cations; ii) total concentrations of major and trace elements; iii) the mineralogical composition of clay and fine silt fractions with a focus on the acidifying ammonium treatments. This work produced original findings on the magnitudes of pedogeochemical changes that occurred during the 90 years of the experiment. Regarding previous results on soil-depth impacts, our findings contribute at recounting complementary parts of a same history of soil development. constraint by different fertilization practices. From a pedological point of view, the 42-plots experiment acts as a “pedotron” under real climatic conditions, showing an acceleration of soil processes of the silt Luvisol following different pedological pathways as a function of the applied fertilizer or amendment.A la suite de travaux précédents sur les états pédogéochimiques, les bilans géochimiques et les impacts de la fertilisation dans les horizons profonds du NEOLUVISOL de lœss du dispositif des 42 parcelles d’INRAE (van Oort et al., 2016, 2017, 2020), nous examinons ici des aspects chronologiques d’évolutions intervenues en surface des sols depuis 1928. Pour cela, des séries d’une quinzaine d’échantillons de la collection historique ont été analysées pour une dizaine de traitements représentatifs : engrais à effet acidifiant (sulfate et phosphate d’ammonium), engrais à effet dispersant (nitrate de sodium, sylvinite, chlorure de potassium), superphosphate, amendements à effet alcalinisant (scories de déphosphoration, carbonate de calcium), fumier de cheval, ainsi que deux parcelles témoins’, sans apport. Nous abordons l’évolution temporelle i) des paramètres édaphiques : teneur en carbone organique et en argile, pH, CEC et garniture cationique ; ii) des teneurs totales en éléments majeurs et en trace ; iii), de la composition minéralogique de fractions argileuses et limoneuses, notamment dans le cas des traitements acidifiants. Les résultats, nombreux et souvent originaux, permettent d’apprécier l’ampleur des évolutions durant les 9 décennies d’expérimentation. Par rapport aux résultats antérieurs sur les impacts en profondeur, ces données contribuent à retracer des parties complémentaires d’une même histoire d’évolution, contrainte par les différents traitements de fertilisation. Vu sous un angle pédologique, le dispositif des 42 parcelles œuvre comme un « pédotron » en conditions réelles, mettant en évidence une accélération des processus d’évolution du sol limoneux selon différentes voies de la pédogenèse, en fonction de la nature des matières fertilisantes apportées