Performed tests showed that at 298 K hard coals sorb relatively small amounts of hydrogen. Those amounts depend on carbon and oxygen content in tested coals. The most considerable amounts of hydrogen are sorbed by coals characterized by strong surface hydrophobicity and high content of aliphatic hydrocarbons. The hydrophilic nature of coal surface does not lead to higher sorption of hydrogen. It was found that the change in amount of sorbed hydrogen is closely related to the moisture. For high moisture coal a significant decrease in hydrogen sorption is observed. Also tests on hydrogen desorption on hard coals were carried out using method of lowering hydrogen pressure above the sorbent. Obtained results showed that tested coals desorb various amounts of hydrogen. Process of sorption is reversible only for some coals, while for the others the desorption isotherm partially lies beneath the sorption isotherm, which indicates that in addition to hydrogen some other chemical substances are emitted from coal.

A B S T R A C T:The fluorination of montmorillonite by aqueous ammonium bifluoride solution (NH4HF2) has been investigated by chemical, sorptive, porosimetric and electron microscopic methods. Changes in the chemical composition of the montmorillonite during the fluorination were compared both in the crystal surface and in the bulk sample. The accumulation of fluorine was distinctly zonal, being present mainly in the surface layers. The electron microscope studies showed that the 300--400 nm thick macrodomains in the initial montmorillonite were cracked into small microdomains 20-30 nm in thickness, this resulting from disruption in the continuity of the octahedral sheets. These distinct changes in morphology of the montmoriUonite aggregates particularly influenced the porosity and sorptive properties.

This paper presents a quantitative characterization of the effects of oxidiation on the surface of coal based on water sorption measurements. Two coals of different rank were examined before and after oxidation with H2O2 and KMnO4. A theoretical model describing sorption equilibria, as the effect of adsorption in submicropores and absorption in the elastic phase of coal, was applied to evaluate structural and enegetic parameters of the sorption systems. Oxidation results in a noticeable increase in the adsorption capacity of the studied coals and practically does not affect the absorption. This is due to creation of new oxygen-containig surface groups on the coal surface, as was shown by XPS measurements. A significant increase in the adsorption energy together with much smaller changes in concentration of water molecules on the coal surface was seen. This suggests an increase in the number of double bonds between adsorbed water molecules and oxygen-containig surface groups.

In this paper results of investigations of sorption of hard coal samples collected from the extracted coal seams of Polish coal mines are presented. As sorbate propane was used. Examinations were carried out in the temperature of 298 K by means of volumetric assessment with the use of apparatus ASAP 2010 of Micromeritics. On the basis of conducted examinations it has been found out that the amount of sorbed propane depend on a type of coal, its metamorphism grade, content of oxygen element, moisture and porosity of these coals. The greatest amounts of propane are sorbed by low carbonized, high-porosity coals of high content of oxygen and moisture. Sorption of relatively high amounts of propane by these coals (ca. 10 cm 3 /g) is a result of the influence of polar surface of coals with molecules of propane and good availability of internal microporous structure of these coals for molecules of examined sorbate. Medium and high carbonized coals sorb insignificant amounts of propane. These coals have compact structure and non-polar character of their surface, their internal porous structure is to a minor degree available for propane molecules in conditions of carried out research. Sorption of propane in this case, takes place mainly in surface pores and on the surface of coals. Moreover, measurements of desorption isotherms of propane showing irreversible character of sorption were made. Desorption isotherms do not come together with sorption isotherms forming open hysteresis loop. Amounts of non-desorbing propane remaining in the coal depend on the type of examined coal.Keywords: hard coal, propane, sorption, desorption W pracy przedstawiono wyniki badań sorpcji próbek węgli kamiennych pobranych z eksploatowanych pokładów węglowych polskich kopalń. Jako sorbat zastosowano propan. Badania przeprowadzono w temperaturze 298 K metodą objętościową z wykorzystaniem aparatu ASAP 2010 firmy Micromeritics. Na podstawie przeprowadzonych badań stwierdzono, że ilości sorbowanego propanu są zależne od rodzaju węgla, jego stopnia metamorfizmu, zawartości pierwiastka tlenu, wilgoci i porowatości tych węgli. Największe ilości propanu sorbują węgle niskouwęglone, wysokoporowate o dużej zawartości tlenu i wilgoci. /g) jest wynikiem oddziaływania polarnej powierzchni węgli z cząsteczkami propanu oraz dobrej dostępności wewnętrznej mikroporowatej struktury tych węgli dla cząsteczek badanego sorbatu. Węgle średnio i wysokouwęglone sorbują niewielkie ilości propanu. Węgle te mają zwartą budowę oraz niepolarny charakter powierzchni, ich wewnętrzna struktura porowata jest w niewielkim stopniu dostępna dla cząsteczek propanu w warunkach przeprowadzanych badań. Sorpcja propanu w tym przypadku zachodzi głównie w powierzchniowych porach i na powierzchni węgli. Przeprowadzono również pomiary izoterm desorpcji propanu wykazując nieodwracalny charakter sorpcji. Izotermy desorpcji nie zbiegają się z izotermami sorpcji tworząc otwartą pętlę histerezy. Pozostające w węglu ilości nie desorbującego się propanu są zależne od rodzaju badanego węgla.Słow...

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