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vol. 9, nr. 2 (2007)
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Adsorption of water vapour on brown coals of different origin
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Zofia Sokołowska1, Jolanta Kwiatkowska2, Alina Maciejewska2
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1 Institute of Agrophysics, Polish Academy of Sciences, ul. Doświadczalna 4, 20-290 Lublin |
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2 Department of Soil Science and soil Conservation, Warsaw University of Technology |
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vol. 9 (2007), nr. 2,
pp. 481-494
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abstract:
Brown coals origin from Bosnia and Herzegovina, as well as from Poland were studied. The measurements were carried out in a vacuum dryer under static conditions. The evaluation of the specific surface area was performed according to the Polish Standard PZ-Z-19010-1. The highest adsorption of water was exhibited by a coal sample from Konin, Poland, whereas the lowest - by a sample from Livino, Bosnia and Herzegovina. The evaluated adsorption and desorption isotherms are given. The shape of the isotherms was similar for all analysed samples and they could be considered as belonging to type II isotherms according to the BET classification scheme. In all cases a well pronounced hysteresis loop appeared. Its occurrence can be attributed to the existence of mesopores. The obtained experimental data were analysed by using BET and Dubinin isotherm equations. Both equations described the experimental data reasonably well. The amount of water strongly bonded to coals was estimated from the adsorption data at the relative pressures from the range [0.15, 0.35]. However, correlation between the amount of strongly bonded water and the amount of polar functional surface groups was higher when the amount of strongly bonded water was estimated from adsorption at the relative pressure equal to 0.35. The adsorption of water increased proportionally with the square of the amount (concentration) of surface functional groups. On the basis of the studies performed, conclusions were formulated regarding surface properties of coals, as well as valuation of their use for the purpose of soil recultivation, decontamination and improvement.
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keywords:
brown coal, water vapour adsorption, polar functional groups, hygroscopy
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original in:
Polish
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