Determination of water content by means of the Derivatograph

The paper presents possible applications of differential thermal analysis for study of the physicoehemical properties of liquid/solid systems, mainly through programmable liquid thermodesorption from the sample under quasi-isothermal conditions. The results prove its applicability in the determination of solid physieoehemieal properties, and particularly in calculations of adsorption potential distribution, the activation energy of molecules adsorbed on the surface and the surface heterogeneity by means of computer techniques.

Section: Resultsmentioning

confidence: 99%

“…adsorption capacity or porous structure) [1][2][3]. The results of measurements of liquid adsorption and desorption from the gaseous phase and the heats of processes taking place on silica gel surfaces with a derivatograph are presented in [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Application of programmable liquid thermodesorption under quasi-isothermal conditions to study physicochemical properties of liquid films and solid surfaces

Staszczuk

Jaroniec

1992

“…Simon [1] described the applicability of the derivatograph for determination of the adsorption capacity of industrial adsorbents. Das et al [3] recently used the complex method for studies on the change of amorphous silica into crystobalite.…”

mentioning

confidence: 99%

“…Studies have shown that during reaction (1), in addition to changes in the adsorption properties of the silica gel [4,11 ], its texture and skeleton structure may also undergo modification [9,12].…”

mentioning

confidence: 99%

Use of thermal analysis to follow the modification of the skeleton structures of silica gels with alcohols and water vapour

Лебода

1978

Derivatograph was used to follow the modification of the skeleton structures of silica gels with alcohols and water vapour. Analogous investigations were carried out by other independent methods. Agreement between the results is good.The derivatograph is widely used at present in studies on adsorbents [1 -5] and packings of chromatographic columns [6,7]. Simon [1] described the applicability of the derivatograph for determination of the adsorption capacity of industrial adsorbents. Das et al. [3] recently used the complex method for studies on the change of amorphous silica into crystobalite.Utsugi et al. [4,5] have investigated the surface groups of silica gels chemically modified with alcohols by means of differential thermal analysis and thermogravimetry. Silica gels esterified with alcohols are used in chromatographyand in industry. Esterification reactions of hydroxylated silica gels with alcohols R-OH can be presented in a simplified way [9]:Si-OH + R-OH ~_ Si-OR + H20(1)The degree of esterification of the silica gel surface depends on the temperature and time of the reaction, the pressure of alcohol vapour, the water content of the reaction system, and the porosity of the modified xerogel [8][9][10]. Studies have shown that during reaction (1), in addition to changes in the adsorption properties of the silica gel [4,11 ], its texture and skeleton structure may also undergo modification [9,12].In the present paper the derivatograph has been used to follow the modification of the skeleton structure of hydroxylated silica gel with alcohols and water vapour. ExperimentalFor the experiments we used adsorbents obtained by autoclave modification of the hydroxylated silica gel surface with n-alcohols and water vapour. Hydroxylated silica gel was produced by POCh Gliwice (Poland) and additionally purified with HC1. The reactions of the alcohols and water vapour with this silica gel were carried out in an autoclave. The following substances were used as modifying 2*

“…The derivatograph has been used to determine the amount of moisture [10], and also indirectly for the estimation of water adsorption isotherms on solids [11]. The samples investigated were placed in desiccators over sulphuric acid solutions of suitable concentration, i.e.…”

mentioning

confidence: 99%

Determination of liquid vapour adsorption and desorption on and from solids by means of the derivatograph II

Staszczuk¹

1986

Studies of water adsorption and desorption on silica gel with a modified derivatograph are described. The dynamic gas chromatography step profile method was used to determine isotherms of adsorption and desorption from the TG curve. The obtained isotherms agree with those from other methods. The properties of surface liquid layers can be investigated by this method.Kinetic adsorption investigations give valuable information on the filling of macropores and micropores in minerals. The rate of adsorption of a gas or vapour on a solid depends, among other things, on the diffusion coefficient, which in turn depends on many factors, such as the porosity, the granule zone radius, the adsorbate concentration in the carrier gas and in the adsorbent, and the physicochemical properties of the surface [1-3].The desorption ofa vapour or gas from a mineral surface is a reversible process relative to adsorption. The results of desorption process investigations provide interesting conclusions concerning the bonding energy of molecules adsorbed on the solid surface, the activation energy [4,5] or the adsorbed molecules, and the vicinal adsorption layer structure [3].There are two recognized methods of measuring the adsorption and desorption of liquid vapour: static and dynamic.In the static methods [1], the sample investigated is placed in a liquid vapour atmosphere. When equilibrium is attained, the amount of adsorbed vapour and the equilibrium pressure are checked. The difference between the adsorbate introduced John Wiley & Sons, Limited, ChichesterAkad~miai Kiad6, Budapest