Application Of Inverse Gas Chromatography Research Articles

Application of inverse gas chromatography to bench scale flotation of sulphide ore

ABSTRACT Inverse gas chromatography (IGC) is receiving increasing attention due to its high precision and ease of application in determining various characteristics of a wide variety of materials of different shapes and morphologies. This study details an experimental investigation into the application of the IGC technique to the flotation of sulphide minerals. Rather than giving the surface energy, the trends associated with the various concentrates and tailings are described. Bench-scale flotation experiments of a nickel-copper sulphide ore were conducted in a Denver flotation cell. The IGC analyses were carried out on the timed concentrates, as well as on the final tailings, in order to evaluate the correlation between surface energetics and the flotation response of the ore particles. The results indicated that the floatability of the concentrates was directly related to the surface energy of the particles. Both dispersive and specific components of surface free energy increased by increasing the necessary time for the particles to be floated, which was consistent with the obtained values for the work of adhesion to water. However, the flotation response of the tailings was not consistent with the expectations from the surface energy value. The significance of the sample composition, particle size distribution, and their consequences in surface energy-flotation response relationship were also observed.

Application of inverse gas chromatography in the surface characterization of diethanol amine modified polystyrene based polymer.

In the present work, diethanol amine modified polystyrene based polymer (PVBC-Diethanol amine) was synthesized and characterized, then surface properties of the polymer were examined by inverse gas chromatography method at infinite dilution. The retention diagrams obtained based on the interaction of polar and nonpolar probes with the polymer were drawn over a temperature range from 30 to 55 °C. Through the diagrams, the dispersive component of the surface free energy, g S D of the polymer surface, and the specific enthalpy of adsorption, DH A S , of probes on the polymer were also calculated. Lewis acid, K A , and Lewis base, K D , parameters of PVBC-Diethanol amine surface were determined. The values of K A and K D indicated that PVBC-Diethanol amine surface exhibited a basic behavior.

Surface Characterization of Carbonaceous Materials Using Inverse Gas Chromatography: A Review

It is essential to understand the adsorption of guest molecules on carbon-based materials for both theoretical and practical reasons. It is crucial to analyze the surface properties of carbon-based materials with a wide range of applications (e.g., catalyst supports, hydrogen storage, sensors, adsorbents, separation media, etc.). Inverse gas chromatography (IGC) as a powerful and sensitive technique can be used to characterize the surface physicochemical properties (i.e., Brunauer-Emmett-Teller (BET) surface area, surface energy heterogeneity, heat of adsorption, specific interaction of adsorption, work of cohesion, glass transition temperatures, solubility, and so forth) of various types of materials such as powders, films, and fibers. In this review, the principles, common methods, and application of IGC are discussed. In addition, the examples of various experiments developed for the IGC to characterize the carbonaceous materials (such as carbon nanotubes, graphite, and activated carbon) are discussed.

Void forming index: A new parameter for detecting microstructural transformation caused by powder agglomeration

As powder agglomeration during storage causes a decrease in the performance of dry powder inhalers (DPIs), it is important to understand the properties of powder agglomeration in developing DPIs. Generally, powder agglomeration is caused by capillary force and crystalline transformation in conditions of higher humidity. It is, however, difficult to correlate crystalline transformation and powder agglomeration, especially when the crystalline transformation is limited. In this study, we focused on the application of inverse gas chromatography (iGC) to detect powder agglomeration directly. There was a slight change between the powder state and lactose agglomerates using powder X-ray diffraction, and dynamic vapor sorption. On the other hand, a change in pressure drop was found during measurement of lactose using iGC. After measurement by iGC, powdered lactose agglomerated. This finding suggests that a pressure drop is related to powder agglomeration and can be employed to detect the onset of powder agglomeration. Based on these findings, we propose a novel index—the Void Forming Index (VFI)—which is related to the pressure drop with iGC. The VFI is a useful index in the evaluation of powder agglomeration, and will be especially useful during DPI development.

Application of Inverse Gas Chromatography for Diffusion Measurements and Evaluation of Fluid Catalytic Cracking Catalysts

The diffusion rates of feedstocks and intermediate products in fluid catalytic cracking (FCC) catalysts have relevance for the product selectivities obtained from the conversion of feedstocks in the FCC process. A simple and robust method was developed to determine the diffusion of probe molecules in such catalysts by means of inverse gas chromatography. This procedure is described in detail, and its relevance in FCC is illustrated by several examples. It is shown that catalytic properties of FCC catalysts can be rationalized with the diffusion coefficient parameter in cases where traditional analytical tools (nitrogen sorption and X-ray diffraction) reach their limits.

Application of inverse gas chromatography to investigate diffusion resistance in FCC catalysts

application of inverse gas chromatography to investigate diffusion resistance in FCC catalysts

Application of inverse gas chromatography in physicochemical characterization of phenolic resin adhesives

One of the most important stages during production of abrasive tools is their hardening. The degree of hardening is very important and influence toughness of the final product. During hardening process the cross-linking of the phenolic resins, used as a binder, occurs. Nowadays, there is no standard, accurate and simple method for the estimation of the hardening degree of abrasive tools. The procedure of the determination of hardening degree of the binder (phenolic resins) by means of inverse gas chromatography (IGC) was presented in this paper. Results obtained by use of IGC derived method was verified by Soxhlet extraction and by FTIR method. Good agreement was found for results from IGC and Soxhlet extraction whereas those from FTIR were much lower. FTIR method supplies data concerning bulk properties not the surface as in case of IGC and Soxhlet methods. These results indicate that resins are more cross-linked on the surface than inside the material.

Investigation on the surface properties of chemically modified natural fibers using inverse gas chromatography

This paper presents the application of inverse gas chromatography (IGC) technique for characterization and comparison of the surface properties of the natural fibers as reinforcement fillers in wood plastic composites. The effects of chemical modification using 1% NaOH were also studied. The fibers used for this work were Iranian cultivated eucalyptus, spruce, bagasse, and wheat straw. Chemical composition of fibers was found to be modified after treatment as characterized by Fourier transform infrared spectroscopy (FTIR). The crystallinity of fibers and the specific interaction was improved by the alkaline treatment, with more relevance to the agro-fibers. The IGC shows also a general increase in the wettability of the modified fiber when compared with the raw (unmodified) samples. Alkaline treatment achieves the best overall improvement in the properties evaluated of the agro-fibers when compared to the wood fibers.

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.

Application of inverse gas chromatography for polymer characterization

The possibility of polymer characterization by inverse gas chromatography (IGC) was illustrated with the study of sorption properties of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), PGME, synthesized by suspension copolymerization, and copolymer modified with ethylene diamine, PGME-en. The data collected from IGC experiments at infinite dilution are used for the calculation of the thermodynamic parameters of adsorption, dispersive components of the surface free energies, and the acid/base constants. .

Determination of Dispersive Properties of Silicas by Inverse Gas Chromatography: Variation with Surface Treatment

The application of inverse gas chromatography (IGC) to the examination of the surface properties of untreated crystalline and fused silica and surface-treated silicas with silane coupling agents is discussed. The carbon content of the silane coupling agents adsorbed on the surface of the silicas was determined by means of a Carbon Determinator. If the assumption is made that each silane coupling agent molecule occupies an area of 0.5∼1 nm 2 , the adsorption amounts show that multilayers are generally adsorbed onto the silica surfaces. This paper presents and discusses the dispersive properties expressed by γ D S , the dispersive component of the surface free energy, as determined at various temperatures. At the same temperature of IGC measurement, the values of γ D S determined by IGC were lower for the crystalline silica than for the fused silica. This means that crystalline silica is more stable than fused silica. The silica surface-treated with γ-methacryloxy propyl trimethoxy silane (MTMS) shows a relatively high γ D S value(42.75 mJ·m -2 at 160°C). This means that this sample should be compatible with polyester(27 ± 3 mJ·m -2 at 290°C) at high temperature. The silicas that were surface-treated with γ-glycidoxy propyl trimethoxy silane (GMS) and γ-mercapto propyl trimethoxy silane (MCMS) exhibit γ D S values that are in close agreement with those of almost all resin(30mJ·m -2 at 160°C). The γ D S value of the silica surface-treated with γ-amino propyl triethoxy silane (AES) is similar to that of epoxy resin(40mJ·m -2 at 80°C). This means that this sample is compatible with epoxy resin at relatively low temperatures.

Application of inverse gas chromatography in the characterization of raw material used in manufacturing of abrasive materials

The raw material—aloxite used during the manufacturing of grinding tools was characterized by means of inverse gas chromatography (IGC). The surface properties of the different types of aloxite were determined including: (i) the specific surface area; (ii) the dispersive component of surface free energy γ S D as well as the sensitivity of this parameter on the environment humidity; and (iii) acidity and basicity of the examined surfaces. The results of our experiments proved the usefulness of IGC in the characterization of this kind of materials.

Inverse gas chromatographic determination of solubility parameters of excipients

The principle aim of this work was an application of inverse gas chromatography (IGC) for the estimation of solubility parameter for pharmaceutical excipients. The retention data of number of test solutes were used to calculate Flory–Huggins interaction parameter ( χ 1 , 2 ∞ ) and than solubility parameter ( δ 2), corrected solubility parameter ( δ T) and its components ( δ d, δ p, δ h) by using different procedures. The influence of different values of test solutes solubility parameter ( δ 1) over calculated values was estimated. The solubility parameter values obtained for all excipients from the slope, from Guillet and co-workers’ procedure are higher than that obtained from components according Voelkel and Janas procedure. It was found that solubility parameter's value of the test solutes influences, but not significantly, values of solubility parameter of excipients.

Application of Inverse Gas Chromatography and Regular Solution Theory for Characterization of Ionic Liquids

Activity coefficients at infinite dilution of 31 organic compounds in three room-temperature ionic liquids (RTILs) were determined using inverse gas chromatography. The measurements were carried out at different temperatures between 313.15 and 333.15 K. The regular solution theory was used to estimate the solubility parameters of each RTIL. Such a theory was also used to predict the CO2 solubility in a given RTIL and to estimate the upper critical solution temperature of a binary system containing 1-butanol and 1-butyl-3-methylimidazolium hexafluorophosphate. The accuracy of the results obtained indicates that the regular solution theory is a good tool to predict the phase behavior of mixtures containing RTILs.

Application of inverse gas chromatography in the study of the adsorption properties of natural, dealuminated and lead exchanged zeolitic tuffs

Two zeolitic tuffs, Mexican and Hungarian, containing clinoptilolite and mordenite, were characterized by X-Ray diffraction, X-Ray fluorescence spectroscopy, infrared spectroscopy and nitrogen adsorption measurements at 77 K as natural, dealuminated and lead exchanged samples. Adsorption isotherms in the temperature interval 322 K<T<400 K and the thermodynamic parameters $$ - \overline {\Delta H_{ads} } $$ and $$ - \overline {\Delta S_{ads} } /R$$ , Henry's KH and Freundlich's kF adsorption constants were calculated with the aid of inverse gas chromatography (IGC) by the single peak method for the alkanes: C5 to C8 in the low pressure region (p<5 mm Hg). Adsorption isosters and the variation of the isosteric heat of adsorption qisost with surface coverage was further calculated on the basis of the experimental adsorption isotherms treated as analytical functions for individual vapors.

Application of inverse gas chromatography to the examination of annealing processes of semi-synthetic base oils.

The Flory-Huggins chi1,2infinity parameter and solubility parameter delta2 determined by means of inverse gas chromatography (IGC) were successfully used in the physicochemical characterisation of oxidation products of mineral oil-poly-alpha-olefin mixtures. Application of IGC parameters allows one to examine the changes occurring during three different oxidation procedures: classical oxidation in a stainless steel reactor, in a GC column and separate oxidation of the mixture's components. Changes in chi1,2infinity values reflect the changing affinity of mixtures to different types (dispersive, polar, hydrogen bonding) of intermolecular interactions and their potential miscibility and solubility.

Application of inverse gas chromatography to the measurement of diffusion and phase equilibria in polyacrylate–solvent systems

The inverse gas chromatography technique (IGC) was used to determine the partition and diffusion coefficients of ethyl acetate and 2-ethylhexyl acrylate in polyacrylate for both infinite dilution and finite concentrations of solvent. Experiments were performed over a temperature range of 60 to 100°C, more than 100°C above the glass transition temperature of the polymer. The capillary column IGC model previously developed for determining partition and diffusion coefficients of infinitely dilute solvent has been modified to account for the concentration of the solvent in the polymer phase. Thermodynamic data obtained from retention theory and the modified capillary column IGC model are compared.

Application of inverse gas chromatography to characterisation of a polypyrrole surface

Inverse gas chromatography (IGC) was applied to characterise a polypyrrole surface in a capillary column, prepared in situ by chemical vapour deposition. The free energies of adsorption, for a range of n-alkanes, n-alcohols and other polar samples were determined. Two solvation equations were used to correlate the sample retention volumes with sample parameters. The surface of the polypyrrole was found to exhibit a basic nature that determined the interactions with polar volatile compounds.

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

AbstractInverse 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 Å 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 (γSD) of the surface free energy gave an estimation of the surface energy of the slate sample. The obtained values for γSD were 140.0, 124.8, 108.2 and 96.8 mN m-1 at 100, 110, 120 and 130 °C, 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 ηπ parameter and the acid-base (KA, KB) indices. The positive value of ηπ (0.09 kJ mol-1) indicated the presence of Lewis acidic sites on the slate surface. The value of KA (acid index) of 1.17 was higher than the value of KB (base index) of 0.37; this result confirmed the acidic nature of the studied slate's surface.

Examination of surfaces of solid polymers by inverse gas chromatography: 1. Dispersive properties

The application of inverse gas chromatography (i.g.c.) for the examination of surface properties of solid materials is discussed. A group of analogous poly(dimethacrylate)s differing only by the presence and type of the heteroatom in the ester group and two reference polymers were characterized by means of this method. In this paper the dispersive properties expressed by υ s d and C 1 P DS determined at various temperatures (50–70°C) are presented and discussed. It was found that chemically similar polymers may be differentiated in terms of their dispersive parameters. The values of υ s d and C 1 P DS depend on the temperature of the i.g.c. measurement, which is determined by the relative temperature gradient. During heat treatment at 80°C and 160°C, the surfaces of the polymers undergo significant modification depending on the annealing atmosphere (helium or air). This modification is revealed by changes in the dispersive parameters and variations in the relative temperature gradients. The relationship between υ s d and C 1 P DS is linear, but the plots are unique for each polymer.