Inverse Gas Chromatography At Infinite Dilution Research Articles

Evaluation of the surface properties of 4-(Decyloxy) benzoic acid liquid crystal and its use in structural isomer separation.

The selectivity of 4-(Decyloxy) benzoic acid (DBA) liquid crystal in surface adsorption region (303.2–328.2 K) and thermodynamic region (423.2 – 433.2 K) was investigated by inverse gas chromatography at infinite dilution (IGC-ID). The selectivity parameters of the structural isomer series named butyl acetate, butyl alcohol, and amyl alcohol series were calculated for the DBA using IGC-ID technique. Additionally, the surface properties including dispersive surface energy (gS D), free energy (DGA S), enthalpy (DHA S), and acidity-basicity constants were calculated with net retention volumes obtained from IGC-ID experiment results. When the DHA S and DGA S are constants, DBA surface was found to be an acidic character (KD/KA @ 0.89).

Characterization of surface properties of chitosan/bentonite composites beads by inverse gas chromatography

Chitosan/bentonite (CSBt) composites beads were prepared by dropwise of a solution containing chitosan and bentonite to an alkaline NaOH solution. Fourier Transform Infrared Spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, XPS and Brunauer-Emmett-Teller BET analysis have been used to provide new insights on the composition and morphology of CSBt composites beads surface. In this study, inverse gas chromatography (IGC) was implemented to characterize physico-chemical properties of CSBt composites surface. IGC at infinite dilution (IGC-ID) was used to understand the effect of CS on dispersive component of the surface energy of the bentonite. The increasing amount of CS leads to significantly decrease of Bt γsd emphasizing the Bt coating with CS. The IGC at finite concentration (IGC-FC) was also implemented allowing us to reach several parameters such as: specific surface area with organic probes and the distribution functions of the adsorption energy sites on the solid surface. In this case, the most significant decreases were observed in the specific surface area obtained with the octane and isopropanol probes. The distribution function of the adsorption energy sites obtained with isopropanol revealed the decrease in the number of the high energy sites with increase of CS/Bt mass ratio.

Influence of different wet milling on the properties of an attapulgite clay, contribution of inverse gas chromatography

An experimental study, using size measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM) and inverse gas chromatography at infinite dilution (IGC-ID) and finite concentration (IGC-FC) conditions, has been carried out to evaluate, respectively, the changes of particles size, crystalline phases, morphology and surface properties evolution of attapulgite powder after grinding in wet media.The particles size decreases significantly after grinding in ball mill in different liquid media. The SEM analysis shows that the fibers are preserved during grinding in aqueous media. With IGC-ID, after grinding using wet ball milling in hydrochloric acid, the values of γsd determined by injection of alkane probes decrease significantly because of the disappearance of the insertion sites able to retain the probes. In the same grinding conditions, with IGC-FC, the specific surface area obtained with octane probe increases significantly from 114 m2/g to 156 m2/g.

Functionalization of porous siliceous materials, Part 2: Surface characterization by inverse gas chromatography

Surface modification of porous glass beads by ethanol-based 3-mercaptopropyltrimethoxysilane (MPTMS) grafting solutions is directly evidenced by nitrogen adsorption, elemental analysis, thermogravimetry, infrared and 29Si CP MAS NMR spectroscopy. Furthermore, the energetic characterization of the surface is essential to understand comprehensively the physico-chemical interactions between the pristine and MPTMS-modified surface and its gas/liquid-phase environment. In this study, inverse gas chromatography (IGC) is used to characterize the surface properties of porous glass (PG). By means of IGC at infinite dilution (IGC-ID), the dispersive component of the surface energy (γsd), the enthalpy and entropy of adsorption of C6-C10 hydrocarbon probes were determined at temperatures between 30 and 120 °C. The specific component of the surface energy (γssp) at the temperature of 120 °C has been obtained via the Van Oss theory and a least-squares procedure evaluating the IGC data of 8 polar probe molecules collectively. After surface silylation, the total surface energy (γst) decreased from 402 to 255 mJ/m² indicating both a reduced wettability and an increased hydrophobicity of the MPTMS-modified PG. Moreover, the acidity/basicity parameters according to the Van Oss and the Gutmann approach indicated that the acidity of the PG surface decreases by MPTMS grafting.Using n-octane and isopropanol probes, IGC at finite concentration (IGC-FC) was applied to obtain their adsorption isotherms and subsequently the BET specific surface areas. In addition, the surface heterogeneity of the studied PGs was also computed. The energy distribution functions of adsorption sites were monomodal (peak maximum at about 22 kJ/mol) for the n-octane probe, while isopropanol revealed a bimodal distribution function (maxima at about 18 and 25 kJ/mol) on both pristine and MPTMS-modified PG. Furthermore, the proportion of high energy sites (apparently assigned to SiOH groups) has been reduced by surface modification from 65% to only 35% despite a high surface coverage of ˜10 MPTMS species/nm2. These findings are in agreement with the results of 29Si CP MAS NMR measurements and are supported by DFT calculations on the adsorption of isopropanol and n-octane on the surface of a silica cluster model.

Surface characterization of reservoir rocks by inverse gas chromatography: Effect of a surfactant

Abstract The description of the surface chemistry of reservoir rock is essential in understanding the physico-chemical interaction between the rock surface and its environment. In this study, inverse gas chromatography (IGC) is used to characterize the surface chemistry of rocks extracted from four petroleum reservoirs in Algeria. By means of IGC at infinite dilution (IGC-ID), the dispersive component of the surface energy (γ_s^d), the nanomorphological index I_M (χ_t) and the specific component of the surface energy were determined at 100 °C. IGC at finite concentration (IGC-FC) was implemented using n -octane and isopropanol probes, allowing the irreversibility indexes and the adsorption isotherms to be obtained. From the latter, the BET specific surface area and BET constant of the injected probes were determined. Energy distribution functions and indexes of heterogeneity were also computed for the n -octane and isopropanol probes. The results showed that the polar probe, isopropanol, interacts more strongly with the rock surface than the apolar probe. In the second part of this study, the influence of a surfactant used in drilling mud on the heterogeneity of the surface energy was investigated. Different surfactant impregnation ratios were examined by means of IGC-FC. The results indicated that the progressive covering of the solid surface by the surfactant hid chemical functions likely to interact with the injected probes and made the surface smooth by covering the roughness of the surface, which led to the decrease in all parameters obtained by IGC-CF.

Physicochemical characterization of a diatomaceous upon an acid treatment: a focus on surface properties by inverse gas chromatography

Natural diatomite from Sig/Algeria was treated with 0.5, 1.0, 3.0 and 5.0M nitric acid solutions for 2h under reflux at 333K in order to improve its performance as support of catalyst. The purified silica powders obtained from frustules can also be used to reinforce composites. The solids obtained were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR) spectroscopy, thermal analyses, and nitrogen adsorption–desorption at 77K. Treatment of diatomite earth with nitric acid reduced mineral impurities, such as Fe2O3 and alkali metal oxides (CaO, MgO), eliminated carbonates and increased SiO2 ratio from 88% to 98%. The SEM micrographs showed the original geometry of the pores to be preserved. The surface properties were also evaluated using inverse gas chromatography at infinite dilution (IGC-ID) and finite concentration (IGC-FC). The interest here was to establish whether the technique is sufficiently sensitive to detect variations in the surface properties of the diatomite due to this chemical treatment. The IGC analysis permitted to reach several surface energy components with organic probes. Between them, the distribution function of the adsorption energy sites obtained with the isopropanol probe revealed a silica structure after the 5M nitric acid treatment.

Effect of the surface parameters on the interaction of epoxy polymer supports with a lipase enzyme

Four porous polymeric supports prepared from epoxy monomers have been analyzed with respect to their catalytic behavior and characterized by means of infrared spectroscopy (FTIR-ATR), nitrogen adsorption and Inverse Gas Chromatography at Infinite Dilution (IGC-ID). The Pseudomonas stutzeri lipase has been used to determine the adsorption and desorption rates on each support. It has been found that the specific surface area increases with the number of epoxy groups and the pore volume increases as well. The surface energies are also related with the number of epoxy groups in the monomer and show a decrease in the dispersive component of the surface energy, γ S d , from 104.87 to 71.12 mJ m−2, but an increase in the polar or acid–base characteristics. Regarding the adsorption–desorption rates of the enzyme lipase, it occurs in two stages being the short-time processes controlled by the dispersive surface energy of the polymer, but the desorption rate is opposite to the base-to-acid surface energy ratio of the polymer indicating that for long-time processes the enzyme is attached to the polymer surface mainly by acid–base interactions.

Influence of different dry milling processes on the properties of an attapulgite clay, contribution of inverse gas chromatography

The effect of dry milling processes on the surface properties of an attapulgite clay, also called palygorskite, was investigated by carrying out experiments with different types of grinding devices. Ground products were then characterized by size measurement, scanning electron microscopy, X-ray diffraction, adsorption–desorption of N2 and inverse gas chromatography at infinite dilution (IGC-ID) as well as finite concentration conditions (IGC-FC). These analyses were performed to evaluate the changes in particle size distribution, morphology, crystallinity and surface properties of attapulgite powder, respectively. Among the tested dry grinding devices, grinding in an air jet mill (Alpine 50 AS) and a vibratory ball mill (Pulverisette 0) led to the most significant particle size reduction. SEM photomicrographs showed that a breakage of the fibrous structure took place during dry grinding. Moreover, long grinding in Pulverisette 0 resulted in the complete destruction of fibre morphology followed by agglomeration. XRD analysis showed that whatever the grinding process, the microstructure of the attapulgite was not affected. IGC confirmed that only grinding in Pulverisette 0 affected the surface properties notably. In this case, the most significant decreases were observed in the dispersive component of the surface energy (164 to 116mJ/m2) and in the specific surface area obtained with the octane probe (114.5m2/g to 62.6m2/g) by IGC-ID and IGC-FC, respectively. At the same time, a modification of the distribution functions of the adsorption energies (DFAE), giving information about surface heterogeneity, was noticed.

Effect of acid treatment on surface properties evolution of attapulgite clay: An application of inverse gas chromatography

In this paper, the evolution of structural, textural and surface properties of attapulgite after treatment with increasing concentrations of hydrochloric acid (0.5, 1, 3 and 5 M) is reported. The solids obtained were characterized by SEM, XRD, FTIR and BET analysis. The surface properties were also evaluated using inverse gas chromatography at infinite dilution (IGC-ID) and finite concentration (IGC-FC). The IGC analysis permitted us to reach several parameters such as: specific surface area, BET constant with organic probes and the distribution functions of the adsorption energy sites on the solid surface. At dilute concentrations of acid, carbonates are eliminated and the specific surface area increases. However, the morphology and crystal structure of attapulgite are preserved. At higher concentrations of acid, dissolution of octahedral sheets and at the same time formation of an amorphous silica from the tetrahedral sheets occur. However, the fibrous morphology is still preserved. The calculation of distribution functions reveals a clear evolution in the heterogeneity of the surface during the acid treatment, the appearance of shoulders is attributed to the development of strong specific interactions between the injected polar probe and silanol groups on the surface of amorphous silica formed during the acid treatment.

Acid natural clinoptilolite: Structural properties against adsorption/separation of n-paraffins

The employment of an acid natural clinoptilolite (AZH-1) in the adsorption and separation of n-paraffins has been evaluated. Natural clinoptilolite, NZ, was the raw material used to prepare the sodium-exchanged clinoptilolite (AZ) starting from which the AZH-1 sample was obtained by acid treatment. The structural stability of the samples after the applied treatments was demonstrated. The nitrogen adsorption experiments indicated that the acid sample has a homogeneous porous distribution and a considerable increase in the micropore volume with respect to NZ and AZ. The employment of the inverse gas chromatography at infinite dilution (IGCID) allowed studying the adsorption and separation of n-paraffin mixtures on AZH-1. It was also confirmed that the diffusion on AZH-1 took place in an unblocked structure through the A channel of ten members with minimal interactions. The IGCID results demonstrated the capacities of the acid Cuban natural zeolite in the adsorption and separation of n-paraffin mixtures.

Surface dispersive energy determined with IGC-ID in anti-graffiti-coated building materials

Coating building materials with anti-graffiti treatments hinders or prevents spray paint adherence by generating low energy surfaces. This paper describes the effect of coating cement paste, lime mortar, granite, limestone and brick with two anti-graffiti agents (a water-base fluoroalkylsiloxane, “Protectosil Antigraffiti ®”, and a Zr ormosil) on the dispersive component of the surface energy of these five construction materials. The agents were rediluted in their respective solvents at concentrations of 5 and 75% and the values were determined with inverse gas chromatography at infinite dilution (IGC-ID). The dispersive energy of the five materials prior to coating, ranked from highest to lowest, was as follows: limestone > granite > cement paste > brick > lime mortar. After application of the two anti-graffiti compounds, CF 3 terminals (Protectosil) were found to reduce the surface energy of both basic (limestone and lime mortar) and acidic (granite) substrates more effectively than CH 3 (ormosil) terminals.

Influence of Boron Concentration on the Surface Properties of TEOS-PDMS Hybrid Materials

The influence of the concentration of triethylborate (TEB) on the surface properties of hybrid materials prepared from tetraethylortosilicate (TEOS) and polydimethylsiloxane (PDMS) has been studied. TEB concentration has been varied between 0 and 30 wt.% respect to the total amount of alkoxyde whereas PDMS concentration has been set at 40 wt.% in all the hybrid samples. Pore size distributions (PSDs), specific surface areas (SSAs) and surface energies have been determined for such materials. PSDs have shown that pore size and pore volume increase with the amount of TEB forming the hybrid, whereas SSAs decrease. Surface energies have been determined by inverse gas chromatography at infinite dilution (IGC-ID) and have been divided into dispersive and specific surface energies. It was also found that TEB affects to both, dispersive and specific surface energies. Dispersive surface energy values increase from 23.23 mJ⋅m−2 for the pure TEOS-PDMS hybrid sample to 31.07 mJ⋅m−2 for the 30wt.% TEB-containing material. This increase has been attributed to the enhanced polarizability of the TEOS-PDMS hybrid when TEB is incorporated into the structure, a result which is consistent with the composition and structural characterization of the studied hybrid materials. Acid and base (kA, kB) surface constants also evidence a correlation with the TEB concentration: kA decreases and kB increases with the increase of TEB in these hybrids, a result which has been assigned to the lower acidity of boranol groups respect to that of silanols. The formation of an hybrid structure of Si–O–Si(PDMS) and B–O–Si(PDMS) bonds has been confirmed by FT-IR spectroscopy by the presence of a band at 850 cm−1 and a shoulder between 930 and 880 cm−1, respectively.

Characterisation of the surface thermodynamic properties of cement components by inverse gas chromatography at infinite dilution

The surface thermodynamic properties of three main inorganic compounds formed during hydration of Portland cement: calcium hydroxide (Ca(OH) 2), ettringite (3CaO·Al 2O 3·3CaSO 4·32H 2O) and calcium-silicate-hydrates (C-S-H), respectively, and one mineral filler: calcium carbonate (CaCO 3), have been characterised by inverse gas chromatography at infinite dilution (IGC-ID) at 35 °C. The thermodynamic properties have been investigated using a wide range of non-polar ( n-alkane series), Lewis acidic (CH 2Cl 2 and CHCl 3), Lewis basic (diethyl ether) and aromatic (benzene) and n-alkene series molecular probes, respectively. The tested samples are fairly high surface energy materials as judged by the high dispersive contribution to the total surface energy (the dispersive components γ s d range from 45.6 up to 236.2 mJ m − 2 at 35 °C) and exhibit amphoteric properties, with a predominant acidic character. In the case of hydrated components (i.e. ettringite and C-S-H), the surface thermodynamic properties have been determined at various temperatures (from 35 up to 120 °C) in order to examine the influence of the water content. The changes of both dispersive and specific components clearly demonstrate that the material surface properties are activated with temperature. The changes in the acid–base properties are correlated with the extent of the overall water loss induced by the thermal treatment as demonstrated by thermogravimetric analysis (TGA). The elemental surface composition of these compounds has been determined by X-ray photoelectron spectroscopy (XPS).

Influence of the geological history, particle size and carbonate content on the surface properties of talc as determined by inverse gas chromatography at infinite dilution

Inverse gas chromatography at infinite dilution (IGC-ID) coupled with a controlled impregnation by polymer gives access to information about the surface of heterogeneous solids such as talcum powder. A limitation of IGC-ID is that it is mainly sensitive to the high-energy sites, in other words for the talc, to the lateral surfaces. Thus, a progressive impregnation of the surface of talc with a suitable polymer allows saturating the high-energy sites, making the chromatographic probes access less energetic free sites, specifically the basal surfaces. In this paper, impregnation has been made with polyethyleneglycol (PEG) 20000M and allows estimation of the ratio of basal to lateral surface of talc crystals which plays a very important role in many industrial applications for talc. We examine the influence of several parameters on the surface properties of different types of talc. These parameters are the particle morphology of talc (microcrystalline, lamellar or very lamellar structure), the carbonate content and the particle size.

Inverse gas chromatographic study of the surface properties of talc impregnated with different acidic and basic polymers

A severe limitation of inverse gas chromatography at infinite dilution (IGC-ID) is that it is mainly sensitive to high-energy sites making it difficult to obtain information about the surface of heterogeneous solids, e.g. the talc. In this paper, it is shown that a progressive impregnation of the talc surface with a suitable polymer can saturate the high-energy sites making the probes access less energetic free sites, specifically the basal surfaces of talc. Here, such impregnations are carried out using a surfactant (cetyltrimethylammonium bromide (CTAB)), different molecular weights polymers (polyethylene glycol (PEG) 2000, 20 000, 35 000, and 100 000) and polymers with different acidic or basic character (polyethylvinylether (PEVE), polyvinyl chloride (PVC), polymethylvinylketone (PMVK), and polystyrene (PS)). One of the aims of this study is to estimate the ratio of lateral and basal surfaces.

Coupling of inverse gas chromatography at infinite dilution (IGC-ID) with a controlled modification of a solid surface

This paper presents a new method for studying the surface of a heterogeneous solid by inverse gas chromatography at infinite dilution (IGC-ID). After saturating the high-energy sites by impregnation with a suitable polymer, the chromatographic probes visit the low energy sites, which are not visible by conventional IGC-ID. This method has been used to study the two types of surface of talc: lateral and basal surfaces. In the second part of the paper the influence of the structure of the polymer on the impregnation is examined. In particular it is shown that a polymer with a linear structure is more able to fit a rough surface than is a branched or a cyclic polymer.

Surface free energy ( γsd) of active carbons determined by inverse gas chromatography: influences of the origin of precursors, the burn off level and the chemical modification

The dispersive component of the surface free energies ( γ s d) of commercial active carbons (AC) from various origins were determined by inverse gas chromatography at infinite dilution (IGC-ID). This method discriminates clearly the AC produced from wood (and activated/carbonised with phosphoric acid) and those from coconut-shell (carbonised and steam activated at 850°C). The values for the last AC (from coconut) are twice higher than the values for AC of wood origin. The structure and shape of the pores have to be considered to explain these values. It seems that for AC, IGC-ID globally characterises the most energetic micropores. This can be observed, in this work, by two ways: (i) washing of commercial AC (chemically activated) allows to liberate a part of the micropores blocked by soluble phosphate and consequently increases the γ s d value; (ii) modifying coconuts AC by chemical treatment (formamide) results in a strong decrease of both microporosity and γ s d value. On the contrary, thermal activation of the modified AC increases at the same time the microporosity and the surface free energy. Finally, we demonstrate that the IGC method is also an useful tool to monitor in situ the evolutions of the surface properties of carbonaceous materials.