"La presencia de arsénico en el medio ambiente ha sido una de las principales causas de contaminación en aguas superficiales y subterráneas. El arsénico se puede encontrar en cuatro estados de oxidación, como arsénico trivalente (As +3 ), arsénico pentavalente (As +5 ), arsina (As -3 ) y arsénico elemental (As 0 ). Se encuentra principalmente en As +3 y As +5 en aguas subterráneas. Es importante proponer el uso de nuevas tecnologías para la remediación del agua potable contaminada con arsénico. Los materiales compuestos de óxidos e hidróxidos de hierro han sido de gran afinidad con el arsénico, ya que permiten la retención de este metal en su superficie. En el presente trabajo, las membranas de disco porosas MDP’s fueron desarrolladas por un material adsorbente y dos aditivos. El material fue sintetizado y caracterizado, obteniendo un área superficial de 55,005 m 2 . g y un diámetro de poro de 34.11 Å, el material tiene una estructura cristalina y tiende a cambiar su composición química a partir de 281 ° C. Se realizó un diseño factorial 2 3 para obtener las condiciones óptimas para la preparación de las membranas en los factores de material adsorbente goethita (FeOOH), aglutinante (Al 2 O 3 ) y lubricante (C 18 H 36 O 2 ). Las membranas se prensaron a 1.5 toneladas y se sinterizaron a 600 °C, convirtiendo el material de goethita (FeOOH) a hematita (Fe 2 O 3 ). Las condiciones óptimas se obtuvieron con un área superficial de 49,44 m 2 . g para la membrana MDP6. Se realizó un análisis de difracción de rayos x para corroborar que las membranas están conformadas por hematita, posteriormente a la sinterización se analizó la membrana calcinada a 600 oC y se obtuvo un área superficial del 39.4249 m 2 . g y un diámetro de poro de 83.01 Å. Finalmente se realizó la cinética de adsorción para cinco membranas con las mismas características de la membrana MDP6. De acuerdo a la cinética se observó que la membrana MDP2 mostró una eliminación del 41% de arsénico (As (V) a una concentración de 0.49 mg/L." | "The presence of arsenic in the environment has been one of the main causes of contamination in surface and underground water. Arsenic can be found in four oxidation states, such as trivalent arsenic (As +3 ), pentavalent arsenic (As +5 ), arsine (As -3 ) and elemental arsenic (As 0 ). It is mainly found as As +3 and As +5 in groundwater. It is important to propose the use of new technologies for the remediation of drinking water contaminated with arsenic. The materials composed of oxides and hydroxides of iron have been of great affinity to the arsenic, since they allow the retention of this metal in its surface. In the present work, MDP’s membranes were developed by an adsorbent material and two additives. The material was synthesized and characterized, obtaining a surface area of 55.005 m 2 . g and a pore diameter of 34.11 Å, the material has a crystalline structure and tends to change its chemical composition from 281 oC. A 2 3 factorial design was performed for to obtain the optimal conditions for the preparation of the membranes for the factors of adsorbent material goethite (FeOOH), Binder (Al 2 O 3 ) and Lubricant (C 18 H 36 O 2 ). The membranes were pressed to 1.5 tons and sintered at 600 °C, converting the goethite material (FeOOH) to hematite (Fe 2 O 3 ). X ray diffraction was performed to verify that the material changes from phase to hematite by sintering at high temperatures. After sintering, the membrane was analyzed by physisorption of nitrogen and was obtained a surface area of 39.4249 m 2. g and a pore diameter of 83.01 Å. Finally the adsorption kinetics was performed for five membranes with the same characteristics of the MDP6 membrane. According to the kinetics, it was observed that the MDP2 membrane showed an elimination of 41% of arsenic (As (V) at a concentration of 0.49 mg L -1 ."

The study of the different biotic and abiotic processes involved in the current formation of Fe-stromatolites in rivers affected by acid mine drainage (AMD) is essential not only to understand this unique and extreme environment, but also to achieve a better understanding of the past iron formation on the Earth and on Mars. The Fe-stromatolites studied in the highly polluted AMD in Tharsis, SW Spain, revealed a unique mineral assemblage with jarosite and rostite as the most unexpected Fe and Al phases and goethite and schwertmannite as the main constituents. Seasonal variations in this region greatly affected the composition of the precipitates and the distribution of diatoms within the Fe-stromatolites. Drought and flood events were also recognized in the sedimentary textures and in the mineral assemblages observed of particular layers within the Fe-stromatolites. The characterization of the chemical and mineralogical composition of Fe-stromatolites in Tharsis as well as the different formation mechanisms proposed complement the existing literature on newly-formed Fe-stromatolites and provides new observations to increase our understanding of those extreme environments.