Application of inverse gas chromatography to the study of the surface properties of modified layered minerals

Abstract--Inverse gas chromatography (IGC) at zero surface coverage was used for determining the surface characteristics of a slate sample. Previously this sample had been characterized by means of X-ray diffraction (XRD), chemical analysis, infrared (IR) spectroscopy and nitrogen adsorption. Quartz, muscovite and chlorite were the minerals foming the slate. A well-defined mesoporous structure with pores of 15 /~ of interlayer distance was observed. Chemical analysis and IR spectroscopy corroborated the X-ray results. The surface characteristics of the slate were defined in relation to nonspecific and specific interactions with organic molecules. In accordance with the nonspecific interactions, the London component ('~s D) of the surface free energy gave an estimation of the surface energy of the slate sample. The obtained values for ~s ~ were 140.0, 124.8, 108.2 and 96.8 mN m i at 100, 110, 120 and 130 ~ respectively. These values were characteristic of an inorganic sample of high surface energy. The values of the thermodynamic variables--differential heat of adsorption, free energy and entropy of adsorption--were in accordance with these results. At the same time, specific interactions were characterized by the e~ parameter and the acid-base (KA, Ks) indices. The positive value of e, (0.09 kJ mol 1) indicated the presence of Lewis acidic sites on the slate surface. The value of K A (acid index) of 1.17 was higher than the value of K B (base index) of 0.37; this result confirmed the acidic nature of the studied slate's surface.

Section: /T ( K -1)supporting

confidence: 54%

Application of Inverse Gas Chromatography to the Study of the Surface Properties of Slates

Rodriguez

1997

“…1994;Okada et al 1990) of polymer-clay composites. Microporous materials based on inorganic matrices and carbonized polymers have been described by Bandosz and co-workers (Bandosz et al 1992a(Bandosz et al , 1992b(Bandosz et al , 1993Putyera 1994). All of these studies, howt Current address: Department of Chemistry, CalTech, Pasadena, California 91125.…”

Section: Introductionmentioning

confidence: 99%

Polyvinyl Alcohol-Clay Complexes Formed by Direct Synthesis

Carrado

Thiyagarajan

Elder

1996

Abstract--Synthetic hectorite clay minerals were hydrothermally crystallized with direct incorporation of a series of five water-soluble polyvinyl alcohols (PVA) of molecular weights from 9000-146,000. The molecular weight of PVA had little effect on the success of hydrothernlal hectorite synthesis, d-spacing or the amount of polymer incorporated. The basal spacings range from 19.5 A to 20.8 A and the amount of polymer incorporated ranges from 20 wt.% to 23 wt.%. Incorporation of PVA within the clay interlayers, along with Li(I) ions to compensate the lattice charge, is indicated. Thermal gravimetric analysis and small angle neutron scattering were used to further examine the polymer-clay systems. Small PVAclay crystallites that are coated with excess PVA are indicated. Removal of the polymer does not alter the extended synthetic clay network, and the nitrogen BET surface area increases from <5 m2/g to >200 m2/g.

“…The poly(4-styrenesulfonate) polyanion introduced between the layers of hydrotalcite causes a significant increase in d00J limited only by the size of the 4-styrenesulfonate molecule that is cross-linked between sheets by chemical bonds. The interlayer space increased up to 1.5 nm (Bandosz et al, 1993) which is a significant value if we consider the structure of clay minerals (Burrer, 1978). Calcination of the hydrotalcite samples in the presence of poly(4-styrenesulfonate) polyanion lead to an increased interlayer distance compared to the initial carbonate forms.…”

Section: Resultsmentioning

confidence: 99%

“…Copyright 9 1994, The Clay Minerals Society scribed in our previous work (Bandosz et al, 1993). It has been found that cationic (intercalated montmorillonites) and anionic (synthetic hydrotalcite-like structures) clays are useful candidates as molecular matrices for carbons.…”

Section: Introductionmentioning

confidence: 99%

Sorption Properties of Carbon Composite Materials Formed from Layered Clay Minerals

Putyera

Bandosz

Jagiełło

et al. 1994

Self Cite

Abstract--The sorption properties of carbon-composite materials based on montmoriUonite and hydrotalcite matrices have been studied using nitrogen adsorption isotherms and inverse gas chromatography. Carbon composite materials derived from both types of inorganic precursors contain pore structure accessible for adsorbate molecules. Adsorption capacity per unit mass of these composite adsorbents is larger in the case of hydrotalcite than in montmorillonite-based materials. Exposing these materials to ambient conditions results in their hydration. Subsequent water removal by heating under vacuum increases nitrogen adsorption capacity, which is explained by the opening of the adsorption space. The water content of hydrated samples and its effect on adsorption capacity is greater for the case of hydrotalcite-based materials. No direct relationship between carbon content and adsorption properties of the materials studied is observed.