Baseline studies of the clay minerals society source clays: Specific surface area by the Brunauer Emmett Teller (BET) method

Doğan, A. Umran; Doğan, Murat; Önal, Müşerref; Sarıkaya, Yüksel; Aburub, Aktham; Wurster, Dale Eric

doi:10.1346/ccmn.2006.0540108

Cited by 179 publications

(91 citation statements)

References 60 publications

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“…Non-polar molecules, such as nitrogen, are known to only adsorb to the external surfaces of montmorillonite and thus provide a direct measurement of the external surface area including clay microstructure (Hendricks et al, 1940;Mooney et al, 1952;Pennell et al, 1992). The BET surface area for SWy-2 is 318.2(±2.2) cm 2 /mg (Dogan et al, 2006), as reported by the Clay Mineral Society and independently confirmed by the authors by BET analysis using a volumetric expansion technique with nitrogen as the adsorbate. The calculated BET surface area was within the uncertainty reported by the Clay Mineral Society.…”

Section: Clay Surface Areasupporting

confidence: 57%

Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral

2007

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Abstract. Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Our results show that while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Additionally, results from this study show that the initial uptake efficiency for butanoic (butyric) acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the initial uptake efficiency of formic, acetic and propanoic (propionic) acids increases only slightly at higher humidities. However, the initial uptake efficiency decreases significantly in a short amount of time due to surface saturation effects. Thus, although the initial uptake efficiencies are appropriate for initial times, the fact that the uptake efficiency will decrease over time as the surface saturates should be considered in atmospheric models. Surface saturation results in sub-monolayer coverage of organic acid on montmorillonite under dry conditions and relevant organic acid pressures that increases with increasing humidity for all organic acids studied. Additionally, the presence of large organic acids may slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of orCorrespondence to: C. D. Hatch (courtney-hatch@uiowa.edu) ganic acids on swelling clay minerals provides an important irreversible heterogeneous sink for these species.

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Section: Clay Surface Areasupporting

confidence: 57%

Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral

2007

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“…It was used without further purification. Its CEC value was 123 ± 3 mmol/100 g (Borden and Giese 2001) as determined by the ammonium acetate method, its layer charge being 0.32 equiv/mol per (Si,Al) 4 O 10 unit (Mermut and Lagaly 2001) and its external surface area being 65 m 2 /g (Dogan et al 2006). The MB used (CAS #7720-79-3) was purchased from Sigma-Aldrich (St. Louis, MO, U.S.A.).…”

Section: Methodsmentioning

confidence: 99%

Intercalation of Methylene Blue in a High-Charge Calcium Montmorillonite — An Indication of Surface Charge Determination

Wang

Jiang

2010

Adsorption Science & Technology

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ABSTRACT:The suitability and applicability of using Methylene Blue (MB), a cationic dye, for cation-exchange capacity (CEC) and specific surface area (SSA) determinations has been studied extensively. Although many workers have reported satisfactory results between the CEC determined by the MB method and other methods, large discrepancies among CEC values determined by different methods are also found in the literature. The work reported herein was focused at elucidating the interlayer configuration of adsorbed/intercalated MB in SAz-1, a high-charge montmorillonite, using MB adsorption, exchangeable cation desorption, counterion (Cl -) adsorption, X-ray diffraction (XRD) and Fouriertransform infrared (FT-IR) analyses.A complete balance between the amount of MB cation adsorbed and that of exchangeable cations desorbed at a 1:1 charge ratio for MB uptake by SAz-1 indicated that cation-exchange was the most important mechanism in this case together with supplementary hydrogen bonding. The adsorbed MB molecules associated into dimers and were orientated in the interlayer in a nearly vertical configuration, with the sulphur atom keyed onto the surface. In a vertical orientation, the MB dimer occupies a projected area of 120-130 Å 2 , similar to the surface area of 130 Å 2 previously assumed from SSA determinations for the horizontally aligned MB molecule. Hence, it is the charge density rather than the horizontal configuration of the MB molecules that controls the MB adsorption capacity. As such, the CEC determination of swelling clays using the MB adsorption method is justified. However, SSA determination by the MB method is correct only if the charge density is less than the projected area of 120-130 Å 2 for an MB dimer. This suggests that the previous assumption of the adsorption of a horizontally orientated MB molecule onto the surface of clay minerals is questionable.

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“…6 Surface areas of clays are typically measured by the BET method, 7 in which the adsorption isotherms are found by exposing the clays to inert gases. [8][9][10] In a study of the microporosity of montmorillonites, D.W. Rutherford et al 11 concluded that the interlayer space of montmorillonites exchanged with small metal cations (such as Na + ), is too narrow to be accessible even to small nonpolar gases (like N2).…”

Section: Introductionmentioning

confidence: 99%

X-ray Studies of Carbon Dioxide Intercalation in Na-Fluorohectorite Clay at Near-Ambient Conditions

et al. 2012

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We show experimentally that gaseous CO2 intercalates into the interlayer space of the synthetic smectite clay Na-fluorohectorite at conditions not too far from ambient. The mean interlayer repetition distance of the clay when CO2 is intercalated is found to be 12.5 Å for the conditions -20 °C and 15 bar. The magnitude of the expansion of the interlayer upon intercalation is indistinguishable from that observed in the dehydrated-monohydrated transition for H2O, but the possibility of water intercalation is ruled out by a careful analysis of the experimental conditions and repeating the measurements exposing the clay to nitrogen gas. The dynamics of the process is observed to be dependent on the pressure, with a higher Page 2 of 15 intercalation rate at increased pressure. The rate of CO2 intercalation at the studied conditions is found to be several orders of magnitude slower than the intercalation rate of water or humidity at ambient pressure and temperature.

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Baseline studies of the clay minerals society source clays: Specific surface area by the Brunauer Emmett Teller (BET) method

Cited by 179 publications

References 60 publications

Heterogeneous uptake of the C<sub>1</sub> to C<sub>4</sub> organic acids on a swelling clay mineral

Heterogeneous uptake of the C<sub>1</sub> to C<sub>4</sub> organic acids on a swelling clay mineral

Intercalation of Methylene Blue in a High-Charge Calcium Montmorillonite — An Indication of Surface Charge Determination

X-ray Studies of Carbon Dioxide Intercalation in Na-Fluorohectorite Clay at Near-Ambient Conditions

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Baseline studies of the clay minerals society source clays: Specific surface area by the Brunauer Emmett Teller (BET) method

Cited by 179 publications

References 60 publications

Heterogeneous uptake of the C&lt;sub&gt;1&lt;/sub&gt; to C&lt;sub&gt;4&lt;/sub&gt; organic acids on a swelling clay mineral

Heterogeneous uptake of the C&lt;sub&gt;1&lt;/sub&gt; to C&lt;sub&gt;4&lt;/sub&gt; organic acids on a swelling clay mineral

Intercalation of Methylene Blue in a High-Charge Calcium Montmorillonite — An Indication of Surface Charge Determination

X-ray Studies of Carbon Dioxide Intercalation in Na-Fluorohectorite Clay at Near-Ambient Conditions

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Heterogeneous uptake of the C<sub>1</sub> to C<sub>4</sub> organic acids on a swelling clay mineral

Heterogeneous uptake of the C<sub>1</sub> to C<sub>4</sub> organic acids on a swelling clay mineral