Removal of lead(II) from aqueous solution using modified palygorskite, contribution of inverse gas chromatography.

Four modified palygorskite powders that had been milled in mortar, in air jet mill, in Pulverisette0 vibrating ball mill and treated with hydrochloric acid were used as adsorbents for lead removal from an aqueous solution. The adsorbents were characterized by nitrogen adsorption, size measurement, mercury porosimetry and scanning electron microscopy. Inverse gas chromatography at infinite dilution and finite concentration was also implemented to determine surface properties of the four samples, in particular the irreversibility indexes, a measurement of high-energy sites. In a second part, batch adsorption experiments were carried out to study the effect of mechanical and chemical treatments on lead adsorption properties of the powder. The isotherm analysis indicated that the Langmuir model could represent the adsorption data. The sample ground in Pulverisette0 presented the highest cationic exchange capacity and led to the highest adsorption capacity despite the relatively low specific surface area and the complete destruction of the fibrous morphology of the raw powder. A correlation was shown between the cationic exchange capacity and irreversibility indexes obtained with isopropanol.

Study by inverse gas chromatography of the surface properties of milled graphites.

A graphite was milled during 1, 2, 3 and 4h. The milled samples were then examined using inverse gas chromatography (IGC), at infinite and finite concentration conditions. The present work reports the study of the surface properties by IGC of milled graphite samples as a function of the milling time parameter and of the oxygen content.

Influence of poly(methyl methacrylate) impregnation ratio on the surface properties of fumed silica and on the glassy temperature of poly(methyl methacrylate) using inverse gas chromatographic analysis.

The surface properties of poly(methyl methacrylate) (PMMA) impregnated fumed silicas, in a large range of impregnation ratios, were examined using inverse gas chromatography at infinite dilution. It was observed that the dispersive component gamma(s)d does not decrease monotonously with the impregnation ratio. Two critical coverage ratios were evidenced corresponding at first to the shielding of the most energetic sites and then to the achievement of total coverage of the silica surface. The influence of the coverage ratio on the glassy temperature (tg) of the adsorbed PMMA was also studied, which was evidenced down to a very low coverage ratio (1 monomer unit/nm2).

Characterization of Silylated Silicas by Inverse Gas Chromatography: Modelization of the Poly(dimethylsiloxane) Monomer Unit/Surface Interactions Using Poly(dimethylsiloxane) Oligomers as Probes

Inverse gas chromatography (IGC) at infinite dilution was used to characterize the fumed silica surface. The silica was modified by chemical treatment with either dimethyldichlorosilane or trimethylchlorosilane. To observe the silica and poly(dimethylsiloxane) (PDMS) interactions, we used apolar (alkanes) and polar probes (chloroform, benzene, tetrahydrofuran, etc.), but also model molecules of PDMS such as linear and cyclic oligomers of PDMS with two to five monomer units. It is shown that PDMS oligomers are very appropriate to discriminate the silylated silicas.