Smectite fluorination and its impact on interlayer water content and structure: A way to fine tune the hydrophilicity of clay surfaces?

Tuning the Hydrophobicity of Layer-Structure Silicates To Promote Adsorption of Nonaqueous Fluids: Effects of F– for OH– Substitution on CO2 Partitioning into Smectite Interlayers

“…38 These conclusions are in good agreement with the experimental IR and H2O sorption study of Schnetzer et al, 18 which shows that OHin hectorite is responsible for increased affinity towards H2O based on changes in the frequency of the δ(Al-OH-Mg) band. The 30% decrease in interlayer H2O content at ambient conditions due to Ffor OHsubstitution reported by Dazas et al 16 is very similar to the differences at 2L basal spacings for complete Fand OHsubstitution in our simulations. The progressively larger energy barrier to H2O intercalation into collapsed hectorite interlayers with increasing F -/(F -+OH -) ratio found here is also in good agreement with the different slopes of the H2O sorption isotherms for OHand Fhectorites observed by Dazas et al 16 The increase in equilibrium basal spacing in the 2L region with increasing F -/(F -+OH -) ratio is probably driven by a need to increase the total number of interlayer H2O molecules to develop a stable, more integrated H-bonding network.…”

“…This behavior is consistent with the experimental observation of increasing hydrophobicity of smectites with increasing Fcontent. 16,17 The computed intercalation behaviors of CO2 and H2O individually vary greatly with the F -/(F -+OH -) ratio, with the CO2/(CO2 + H2O) ratio increasing with increasing Fsubstitution at all basal spacings > ~11.5 Å (Figures 3 and 4). For all systems, neither H2O nor CO2 intercalate at basal spacings less than ~10.2 Å. H2O adsorption starts at ~10.3 Å, and the basal spacing at which CO2 intercalation begins decreases from 11.2 Å to 11.0 Å with increasing F -/(F -+OH -) ratio.…”

Unraveling the Coupled Processes of (De)hydration and Structural Changes in Na+-Saturated Montmorillonite

“…[5][6][7][8] At low moisture content the crystalline swelling of smectites is a stepwise expansion of the layer-to-layer distance, leading to the well-known 1W, 2W and 3W hydration states with increasing basal spacings (d 00l ) that can be observed by X-ray diffractometry (XRD). 5,[9][10][11][12][13][14][15][16] Leonard and Weed (1967) and Low et al (1970) firstly reported an additional increase of the b-dimension with increasing water content for vermiculite in 1W and 2W and for Na-saturated montmorillonite at water contents up to 2000%. [17][18] The expansion of the b-dimensions of the unit cell was observed by XRD.…”

EXAFS and XRD studies in synthetic Ni-fluorohectorite

“…47 However, one of the most studied, although not yet completely understood complex system, is the 48 interaction between water and the clay mineral. The process of water intercalation is highly 49 dependent on the interlayer cation as well as on the layer charge (Dazas et al, 2013;Gates, 2006; 50 Gates et al, 2012) and it has been studied by many techniques such as X-ray diffraction (XRD) 51 (Wada et al, 1990), X-ray absorption fine structure (XAFS) (Ashley and Doniach, 1975; Lee and 52 Beni, 1977; Lee and Pendry, 1975;Schaich, 1973), nuclear magnetic resonance (NMR) (Tenorio et 53 al., 2010(Tenorio et 53 al., , 2008 and Quasi-elastic Neutron Scattering (QENS) (Bordallo et al, 2008;Gates et al, 54 2012). 55…”