Hydrothermal macroscopic Fe-sepiolite from Oujda Mounts (Middle Atlas, Eastern Morocco)

Arranz, Enrique; Lago, M.; Bastida, J.; Galé, Carlos; Soriano, Jesús; Ubide, Teresa

doi:10.1016/j.jafrearsci.2008.05.002

Cited by 9 publications

(5 citation statements)

References 39 publications

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“…Al 2 O 3 is present in most sepiolites. Only a few references report sepiolite with no Al (Arranz et al, 2008;Imai and Otsuka, 1984;Mayayo et al, 1996;Muraoka et al, 1958). This oxide could reach as much as 8.9 wt% (Rogers , 1956).…”

Section: Chemical Composition Of Sepiolitementioning

confidence: 99%

“…Several of them are from Japan and they appear in dolomitic rocks. The most Fe-rich sepiolites are from Middle Atlas of Morocco (Arranz et al, 2008) and from Tyrol (Brauner and Pressinger, 1956;Preisinger, 1957). In both locations, the Fe 2 O 3 /MgO ratio is greater than 1 and the Fe 2 O 3 content is $ 20 wt%.…”

Section: Chemical Composition Of Sepiolitementioning

confidence: 99%

“…1. Akbulut and Kadir (2003), Aqrawi (1993), Pérez et al (1989), Argast (1989), Arranz et al (2008), , , Bonatti and Joenssu (1968), Bonatti et al (1983), Botha and Hughes (1992), Boules et al (1971), Bradley (1940), Brauner and Pressinger (1956), Caillère (1936Caillère ( , 1951, Caillère and Henin (1957, 1961, 1972, Caillére and Rouaix (1958), Cetisli and Gedikbey (1960), Chahi et al (1993Chahi et al ( , 1997Chahi et al ( , 2002, Chen et al (2004Chen et al ( , 2008, Corma et al (1987), Dahab and Jarjarah (1989), Drits and Aleksandrova (1966), Dromashko (1953), Ece (1989), Fahey et al (1960), Fersmann (1913), Fleischer (1972), Frank-Kamenetskiy et al (1969), Fukushima and Okamoto (1987), Galán (1987), Galán et al (1975), Galán and Carretero (1999), Galán and Castillo (1984), Galán and Ferrero (1982), Galopim De Carvalho et al (1970), García-Romero and Suárez (2010), García-Romero et al (2004,…”

Section: Introductionmentioning

confidence: 99%

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Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Suárez

Romero

2011

Developments in Clay Science

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Section: Chemical Composition Of Sepiolitementioning

confidence: 99%

Section: Chemical Composition Of Sepiolitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Suárez

Romero

2011

Developments in Clay Science

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“…Sepiolite is a Mg-rich 2:1 trioctahedral clay, characterized by its continuous inverted tetrahedral sheets and discontinuous octahedral sheets, creating a unique ribbon-like structure (Cornejo and Hermosin, 1988; see Figure 1). Although Mg-rich 2:1 trioctahedral clays are relative scarce on the Earth's surface, sepiolite is found in natural low temperature systems (Guggenheim and Krekeler, 2011), including near submarine hydrothermal vents, in lake deposits, in volcanic deposits and in geothermal systems, including the CarbFix Hellisheidi CO 2 storage pilot site (Arranz et al, 2008;. Relatively more Me 2+ is released from divalent metal silicate minerals compared to Si at low pH during the initial dissolution of the mineral.…”

Section: Introductionmentioning

confidence: 99%

An experimental study of sepiolite dissolution rates and mechanisms at 25 °C

Mulders

Oelkers

2020

Geochimica et Cosmochimica Acta

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The steady-state dissolution rates of sepiolite were measured as a function of pH from mixed-flow reactor experiments at 25 o C in both citrate bearing and citrate-free aqueous solutions. Dissolution at pH ≤5.5 and pH ≥9.18 was found to be non-stoichiometric, with relatively more Mg being released at low pH, while Si was preferentially released at high pH. The steady-state dissolution rate of sepiolite at 25 o C, based on Si release rates at far from equilibrium conditions, r + in mol/cm 2 /s at pH ≥4.44 can be described bywhere a i refers to the activity of the subscripted aqueous species. This rate equation is based on a dissolution mechanism by which interstitial Mg is exchanged for 2 H + , followed by the rate limiting release of partially detached Si-tetrahedra. At pH ≤4.44 and in citrate-free aqueous solutions, sepiolite dissolution rates based on Si release are similar to those measured for amorphous SiO 2 despite the fact that the bulk fluid phase was undersaturated with respect to this solid. In contrast, in citrate bearing aqueous solutions, the Si release rate increases with decreasing pH following a trend consistent with the corresponding higher pH values. This difference is attributed to the increase of amorphous SiO 2 dissolution rates in citrate bearing aqueous fluids, preventing the formation of substantial SiO 2 -rich surface layers. To further examine the extent of nonstoichiometric dissolution and its implications on solid phase transformations, batch experiments were performed in citrate bearing aqueous solutions at pH 2.57, 3.40 and 4.31. During these longer term experiments the fluid phase attained saturation with respect to amorphous SiO 2 . From mass balance calculations, Energy-Dispersive X-ray spectroscopy (EDS) and X-Ray powder Diffraction (XRD), it can be inferred that after 688 hours, 98% of the Mg was removed from the solid structure during pH 2.57 batch experiments, while SiO 2 was retained in an amorphous solid phase, demonstrating the independence of the Mg compared to Si release to the aqueous solution.

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“…Micro-X-ray diffraction reveals non-uniformities such as fiber orientation, large variations in the grain size, anisotropy in the orientation of the fibers, and poor crystallinity. Fibrous macroscopic sepiolites have been studied in several works (Arranz et al 2008;Bastida et al 1994;Callen 1984;Yalcin and Bozkaya 2004). An objective of the present work is to reveal differences in the diffractions patterns of sepiolites belonging to these groups, suggesting morphological classifications.…”

Section: Introductionmentioning

confidence: 99%

Variability in sepiolite: Diffraction studies

Río

Romero

Suárez

et al. 2011

American Mineralogist

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Twenty sepiolites of known composition from different origins were analyzed to quantify the variability in structural parameters and its possible relationships with composition and morphology. Morphology SEM analyses led to classify the sepiolites into several groups, beyond the two simple macroscopic or clay groups. X-ray powder diffraction with synchrotron light was used to discuss the variability of the a and b cell parameters with the nature of the cations and occupancy of the octahedral shell. Rietveld refinement using the ideal sepiolite model is performed on sepiolites at two temperatures: 225 °C (for zeolitically dehydrated sepiolite) and 25 °C (for hydrated ambient sepiolite). The latter permitted to locate ca. six molecules of the zeolitic H 2 O within the tunnels.A few samples were selected to evaluate the feasibility and potential of single-crystal diffraction methods: X-ray microdiffraction and electron diffraction. The macroscopic sepiolites gave wellstructured and rich X-ray fiber diffraction patterns, in excellent agreement with ab initio simulations. High-quality single-crystal electron diffraction patterns for three axis zones are indexed and compared with simulations. The experimental and modeling results for X-ray microdiffraction and electron diffraction open a new path for quantitative crystallography on sepiolite and other fibrous clays from the sepiolite-palygorskite group.

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Hydrothermal macroscopic Fe-sepiolite from Oujda Mounts (Middle Atlas, Eastern Morocco)

Cited by 9 publications

References 39 publications

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

An experimental study of sepiolite dissolution rates and mechanisms at 25 °C

Variability in sepiolite: Diffraction studies

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Hydrothermal macroscopic Fe-sepiolite from Oujda Mounts (Middle Atlas, Eastern Morocco)

Cited by 9 publications

References 39 publications

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

An experimental study of sepiolite dissolution rates and mechanisms at 25 °C

Variability in sepiolite: Diffraction studies

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Product

Resources

About

An experimental study of sepiolite dissolution rates and mechanisms at 25 °C