Authors:M. S. Gruszkiewicz, J. M. Simonson, T. D. Burchell, and D. R. Cole
Summary An accurate gravimetric method was used to explore water adsorption/desorption isotherms between 105 and to 250°C for a number of synthetic and natural porous solids including controlled pore glass, activated carbon fiber monoliths, natural zeolites, pillared clay, and geothermal reservoir rocks. The main goal of this work was to evaluate water adsorption results, in particular temperature dependence of hysteresis, for relatively uniform, nano-structured solids, in the context of other state-of-the-art experimental and modeling methods including nitrogen adsorption, spectroscopy, neutron scattering, and molecular simulation. Since no single method is able to provide a complete characterization of porous materials, a combination of approaches is needed to achieve progress in understanding the fluid-solid interactions on the way to developing a predictive capability.
Authors:B. Egrdoğan Alver, M. Sakici, E. Yörükoğullari, Y. Yilmaz, and M. Güven
The water adsorption properties of sepiolite having dolomite supplied from Eskisehir region and their exchanged forms (K+, Na+, Mg2+ and Ca2+) were investigated. The sepiolite samples were characterized using XRD, TG-DTA, DSC and nitrogen adsorption methods. The
temperature ranges were determined for the dehydrations of hydroscopic and zeolitic water as 30–200°C, for the dehydration
of the bound water as 250–750°C and for the dehydroxylation of hydroxyls as 810–850°C in the sample. It was observed that
the value of percent mass loss for natural and modified samples varied in the range from 36.70 to 39.05%. Two mass loss steps
for all samples were observed using a differential scanning calorimetry (DSC) in the range of 30–550°C. Adsorption isotherms
for water on natural and modified forms were obtained at pressures up to 2.39 kPa. Uptake of water increased as K-SEP.<Na-SEP.<Mg-SEP.<Ca-SEP.
for sepiolite samples at 293 K.
We propose to install a balance at the surface of Mars. In this paper we present a survey on tasks which could be accomplished
by means of a balance. The determination of the specific surface area and porosity of Martian soil and other sorption experiments
are discussed. Criteria for the choice of a suitable balance type are given.
Authors:M. Gojić, J. Črnko, M. Sućeska, and M. Rajić
Heat treatment of pipes was performed under industrial conditions at 580C in a dry protective gas containing a CO2–CO–H2–N2 mixture. A commercial adsorbent (733 kg) used for production ofthe gas removed 52.7 l of water in five h and 22.5 min. During
the annealing of pipesoxidation and decarburization were not observed. The results were confirmed bymetallographic analysis.
The values of enthalpy of water desorption (36.4–40.5 kJ mol–1) obtained by DSC and TG measurements were close to those of water evaporation(44.1 kJ mol–1). This suggests that the bonds between the water molecules andadsorbents were not of chemical but of physical nature.
Authors:B. Hunger, S. Matysik, M. Heuchel, E. Geidel, and H. Toufar
We have investigated the interaction of water with Na+-ion exchanged zeolites of different structures (LTA, FAU, ERI, MOR and MFI) by means of temperature-programmed desorption
(TPD). The non-isothermal desorption of water shows, depending on the zeolite type, differently structured desorption profiles.
In every case the profiles have, however, two main ranges. Using a regularization method, desorption energy distribution functions
have been calculated. The desorption energy distributions between 42–60 kJ mol−1, which can be attributed to a non-specific interaction of water, show two clearly distinguished energy ranges. The water
desorption behaviour of this range correlates with the electronegativity of the zeolites and the average charge of the lattice
oxygen atoms calculated by means of the electronegativity equalization method (EEM). The part of the desorption energy distributions
in the range of 60–90 kJ mol−1, reflecting interactions of water with Na+ cations, shows two more or less pronounced maxima. In agreement with vibrational spectroscopic studies in the far infrared
region, it may be concluded that all samples under study possess at least two different cation sites.
Authors:M. Torralvo, Y. Grillet, F. Rouquerol, and J. Rouquerol
Thermodesorption is here considered for its possibility of giving access to the microporosity of adsorbents. The requirements
of this application (good separation of successive desorption steps, good control of the desorption pressure and temperature
throughout the sample, possibility of a safe kinetic analysis of each step) are here fulfilled by carrying out the thermodesorption
in the Controlled transformation Rate Thermal Analysis (CRTA) mode. The method is applied to 4 zeolites (3A, 4A, 5A and 13X)
and a well characterized charcoal, from −25 to 325°C, after pre-adsorption of water.
Authors:E. Robens, B. Benzler, H. Reichert, and K. Unger
Dry cement powder and hardened cement paste were characterised by means of laser granulometry and volumetric measurement of
the nitrogen adsorption isotherm at 77 K. Water sorption isotherms at ambient temperature were measured stepwise by means
of a gravimetric apparatus. The isotherms show a very large hysteresis loop, reaching down to zero relative pressure, which
reflects swelling of the cement gel. Thermoporometric measurements reveal that swelling of that gel consists in water take
up within the continuously growing structure; no stable pore structure could be observed.
Authors:M. Bakass, H. Bahaj, R. Benaddi, and C. Bayane
operating with activated carbon/methanol working pair [ 24 , 25 ].
The choice of an appropriate solid adsorbent depends on several parameters [ 26 ]. It is based essentially on wateradsorption capacity, adsorption kinetics, hydrothermal stability
Authors:Giacomo Perfetti, Thibault Alphazan, W. J. Wildeboer, and Gabrie M. H. Meesters
isotherms are used as tool for measuring the wateradsorption of the bulk coating agent and thus assess the relationship between water content, temperature and humidity.
The effect of temperature on the adsorption–desorption isotherm of Pharmacoat
Authors:G. Lizia Thankam, T.R. Neelakantan, and S. Christopher Gnanaraj
throughout the entire study. Though the increased wateradsorption ratio of the F-GFA resulted in higher water content for the mix, the slump was noted to fall steadily owing to the well graded nature of both OD-F-GFA and AD-F-GFA. The fresh concrete neither