Person:
Astilleros García-Monge, José Manuel

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First Name
José Manuel
Last Name
Astilleros García-Monge
URI
https://hdl.handle.net/20.500.14352/75202
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Cristalografía y Mineralogía
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2003 - 200942010 - 20175
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Now showing 1 - 9 of 9
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    Crystallizationof ikaite and its pseudomorphic transformation into calcite: Raman spectroscopy evidence
    (Geochimica et cosmochimica acta, 2016) Sánchez Pastor, Nuria; Oehlerich, Markus; Astilleros García-Monge, José Manuel; Kalliwoda, Melanie; Mayr, Christoph C.; Fernández Díaz, María Lourdes; Schmahl, Wolfgang W.; Geochemical Society; Elsevier
    Ikaite (CaCO3·6H2O) is a metastable phase that crystallizes in nature from alkaline waters with high phosphate concentrations at temperatures close to 0 °C. This mineral transforms into anhydrous calcium carbonate polymorphs when temperatures rise or when exposed to atmospheric conditions. During the transformation in some cases the shape of the original ikaite crystal is preserved as a pseudomorph. Pseudomorphs after ikaite are considered as a valuable paleoclimatic indicator. In this work we conducted ikaite crystal growth experiments at near-freezing temperatures using the single diffusion silica gel technique, prepared with a natural aqueous solution from the polymictic lake Laguna Potrok Aike (51°57′S, 70°23′W) in Patagonia, Argentina. The ikaite crystals were recovered from the gels and the transformation reactions were monitored by in situ Raman spectroscopy at two different temperatures. The first spectra collected showed the characteristic features of ikaite. In successive spectra new bands at 1072, 1081 and 1086 cm−1 and changes in the intensity of bands corresponding to the OH modes were observed. These changes in the Raman spectra were interpreted as corresponding to intermediate stages of the transformation of ikaite into calcite and/or vaterite. After a few hours, the characteristics of the Raman spectrum were consistent with those of calcite. While ikaite directly transforms into calcite at 10 °C in contact with air, at 20 °C this transformation involves the formation of intermediate, metastable vaterite. During the whole process the external shape of ikaite crystals was preserved. Therefore, this transformation showed the typical characteristics of a pseudomorphic mineral replacement, involving the generation of a large amount of porosity to account for the large difference in molar volumes between ikaite and calcite. A mechanism involving the coupled dissolution of ikaite and crystallization of calcite/vaterite is proposed for this replacement.
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    Nanoscale processes during the interaction of aluminosilicate and carbonate mineral surfaces with acid mine drainage (AMD)
    (Geochimica et cosmochimica acta, 2009) Kollias, K.; Godelitsas, Athanasios; Astilleros García-Monge, José Manuel; Ladas, S.; Kennou, S.; Potamitis, C.; Zervou, M.; Lagoyiannis, A.; Harissopulos, S.; Mavromoustakos, Th.
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    In situ HAFM study of the thermal dehydration on gypsum (010) surfaces
    (American Mineralogist, 2006) Jordan, Guntram; Astilleros García-Monge, José Manuel
    Hydrothermal AFM has been used to study the thermal dehydration reaction on gypsum (010) surfaces in solutions at different saturation states, and in the absence of a bulk liquid phase. Experiments were carried out at temperatures ranging from 25 to 130 °C. Whereas supersaturated solutions (β = 1.8–5) caused gypsum growth in the entire temperature range, solutions close to equilibrium (β = 1.02) caused various responses of the gypsum surface. The most prominent was a sharp transition from fast growth to very fast dissolution at ∼120 °C suggesting a sudden nucleation of a phase more stable than gypsum. No structural relation could be found between the parental gypsum (010) surface and the crystallizing phase. In the absence of a bulk liquid phase, dehydration takes place via the nucleation and spreading of etch-pit like pattern. Laterally, the thermal etch pits spread in an unrestricted way. In the vertical direction, pit growth was limited to a few micrometers. Dehydration by monolayer pits and nucleation of the dehydration process at monolayer steps on the (010) surface were never observed. Thus, unlike growth or dissolution, surface energy related to kink sites or individual point defects seems to be insuffi cient to trigger dehydration. The temperature-dependent lateral pit growth yields an activation energy of 119 ± 11 kJ/mol. The product phase disintegrates at the parental surface into nano-size particles without any morphologically noticeable transition zone.
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    Interaction of Calcium Carbonates with Lead in Aqueous Solutions
    (Environmental science & technology., 2003) Godelitsas, Athanasios; Astilleros García-Monge, José Manuel; Hallam, K.R.; Harissopoulos, Sotirios; Putnis, Andrew
    Pure calcium carbonate (calcite and aragonite) solid materials of different particle size (100-200 ím fragments and millimeter-sized single crystals) were interacted with Pb in aqueous solutions at room temperature under atmosphericPCO2. In the case of the micrometer-sized samples, the macroscopic investigation using a batch-type treatment procedure (solutions between 10 and 1000 mg/L Pb) and ICP-AES, SEM-EDS, and powder-XRD showed that the metal is readily removed from the aqueous media by both materials and indicated the sorption processes (mainly surface precipitation leading to overgrowth of cerussite and hydrocerussite crystals) taking place in parallel with surface dissolution processes. The various processes occurring at the calcium carbonate solid-water interface were clearly distinguished and defined in the case of the millimeter-sized samples interacted with 1000 mg/L Pb using a combination of wet-chemical, in-situ (AFM) and exsitu (AFM, SEM) microscopic, and surface spectroscopic (XPS, 12C-RBS) techniques. The in-situ AFM data revealed the dissolution processes on the surface of the calcium carbonates and the simultaneous heterogeneous nucleation of lead carbonate phases and confirmed the secondary dissolution of lead carbonate crystals grown epitaxially from the initial nuclei. The XPS spectra confirmed that adsorption of Pb occurs simultaneously to dissolution at short interaction times (less than 10 min, prior to precipitation-nucleation/crystal growth) in the case of both CaCO3 polymorphs and that the calcite surface with adsorbed Pb may have an aragonite-type character. The 2CRBS spectra indicated that absorption (incorporation of Pb2+ ions) also takes place in parallel at the surface layers of the calcium carbonates, resulting in formation of solid solutions.
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    A nanoscopic approach to the kinetics of anhydrite (100) surface growth in the range of temperatures between 60 and 120 °C
    (American Mineralogist, 2012) Morales Sánchez-Migallón, Juan; Astilleros García-Monge, José Manuel; Fernández Díaz, María Lourdes
    In situ observations of the growth of the anhydrite (100) surface in contact with supersaturated aqueous solutions under conditions within the stability field of this mineral (60–120 °C) were conducted using a hydrothermal atomic force microscope (HAFM). Advancement rates were measured for [001] steps, the most stable ones on the anhydrite (100) surface. Isothermal data fit well to linear correlations between step advancement rate and supersaturation; the activation energy for step advancement is 73 ± 5 kJ/mol. This is not significantly higher than activation energies reported for the growth of gypsum (60–70 kJ/mol) and does not support that slow dehydration rates of aqueous calcium is responsible for the well-known difficulty to precipitate anhydrite crystals from supersaturated aqueous solutions at temperatures well above the anhydrite-gypsum equilibrium temperature. The role of structural factors that could inhibit the growth of anhydrite is discussed.
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    In Situ Nanoscale Observations of Metatorbernite Surfaces Interacted with Aqueous Solutions
    (Environmental science & technology, 2013) Astilleros García-Monge, José Manuel; Pinto, André Jorge; Gonçalves, Mario A.; Sánchez Pastor, Nuria; Fernández Díaz, María Lourdes
    Metatorbernite (Cu(UO2)2(PO4)2·8H2O) has been identified in contaminated sediments as a phase controlling the fate of U. Here, we applied atomic force microscopy (AFM) to observe in situ the interaction between metatorbernite cleavage surfaces and flowing aqueous solutions (residence time = 1 min) with different pHs. In contact with deionized water the features of (001) surfaces barely modify. However, changes are remarkable both under acidic and basic conditions. In acidic solutions (pH = 2.5) metatorbernite surface develops a rough altered layer and large pits nucleate on it. The altered layer shows a low adhesion and is removed by the AFM tip during the scanning. The large pits spread rapidly, at few tens of nm/s, indicating a collapse of the structure. The combination of dissolution and the presence of defects in the metatorbernite structure can explain both the collapse process and the alteration of the surfaces under acidic conditions. Other mechanisms such as ion exchange reactions remain speculative. In NaOH solutions (pH = 11.5) metatorbernite dissolves by formation of etch pits bounded by steps parallel to ⟨100⟩, the direction of the most straight periodic bond chains (PBCs) in metatorbernite structure. These steps retreat at ∼0.15 nm/s. Under these conditions dissolution is promoted by the formation of stable uranyl carbonate complexes in solution.
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    Interaction of gypsum with lead in aqueous solutions
    (Applied geochemistry, 2010) Astilleros García-Monge, José Manuel; Godelitsas, Athanasios; Rodríguez Blanco, Juan Diego; Fernández Díaz, María Lourdes; Prieto Rubio, Manuel; Lagoyannis, Anastasios; Harissopulos, Sotirios V.
    Sorption processes on mineral surfaces are a critical factor in controlling the distribution and accumulation of potentially harmful metals in the environment. This work investigates the effectiveness of gypsum (CaSO42H2O) to sequester Pb. The interaction of gypsum fragments with Pb-bearing solutions (10, 100 and 1000 mg/L) was monitored by performing macroscopic batch-type experiments conducted at room temperature. The aqueous phase composition was periodically determined by Atomic Absorption Spectrometry (AAS), Ion Chromatography (IC) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP–OES). Regardless of the [Pbaq]initial, a [Pbaq]final < 4 mg/L was always reached. The uptake process was fast (t < 1 h) for [Pbaq]initialP100 mg/L and significantly slower (t > 1 week) for [Pbaq]initial = 10 mg/L. Speciation calculations revealed that after a long time of interaction (1 month), all the solutions reached equilibrium with respect to both gypsum and anglesite. For [Pbaq]initialP100 mg/L, sorption takes place mainly via the rapid dissolution of gypsum and the simultaneous formation of anglesite both on the gypsum surface and in the bulk solution. In the case of [Pbaq]initial = 10 mg/L, no anglesite precipitation was observed, but surface spectroscopy (proton Rutherford Backscattering Spectroscopy, p-RBS) confirmed the formation of Pb-bearing surface layers on the (0 1 0) gypsum surface in this case also. This study shows that the surface of gypsum can play an important role in the attenuation of Pb in contaminated waters.
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    Reaction pathways and textural aspects of the replacement of anhydrite by calcite at 25 °Ck
    (American Mineralogist, 2017) Roncal-Herrero, Teresa; Astilleros García-Monge, José Manuel; Bots, Pieter; Rodríguez-Blanco, Juan Diego; Prieto, Manuel; Benning, Liane G.; Fernández Díaz, María Lourdes
    The replacement of sulfate minerals by calcium carbonate polymorphs (carbonation) has important implications in various geological processes occurring in Earth surface environments. In this paper we report the results of an experimental study of the interaction between anhydrite (100), (010), and (001) surfaces and Na2CO3 aqueous solutions under ambient conditions. Carbonation progress was monitored by glancing incidence X‑ray diffraction (GIXRD) and scanning electron microscopy (SEM).We show that the reaction progresses through the dissolution of anhydrite and the simultaneous growth of calcite. The growth of calcite occurs oriented on the three anhydrite cleavage surfaces and its formation is accompanied by minor vaterite. The progress of the carbonation always occurs from the outer-ward to the inner-ward surfaces and its rate depends on the anhydrite surface considered, with the (001) surface being much more reactive than the (010) and (100) surfaces. The thickness of the formed carbonate layer grows linearly with time. The original external shape of the anhydrite crystals and their surface details (e.g., cleavage steps) are preserved during the carbonation reaction. Textural characteristics of the transformed regions, such as the gradation in the size of calcite crystals, from ~2 mm in the outer region to ~17 mm at the calcite-anhydrite interface, the local preservation of calcite crystalographic orientation with respect to anhydrite and the distribution of the microporosity mainly within the carbonate layer without development of any significant gap at the calcite- nhydrite interface. Finally, we compare these results on anhydrite arbonation with those on gypsum carbonation and can explain the differences on the basis of four parameters: (1) the molar volume change involved in the replacement process in each case, (2) the lack/existence of epitactic growth between parent and product phases, (3) the kinetics of dissolution of the different surfaces, and (4) the chemical composition (amount of structural water) of the parent phases.