Authors:E. Robens, I. Florian, C. Massen, and J. Poulis
The time necessary for the measurement of gas adsorption on a solid can be substantially reduced by using Jäntti's directions for data interpretation. This procedure already delivers results after measuring only a few values of the adsorbed mass. In earlier papers we introduced a second order adaptation to Jäntti's method to broaden its applicability. In the present paper we apply this second order treatment to the adsorption of water vapour from moistened air. Specially we pay attention to the diffusion delay caused by the boundary layer around the sample.
Authors:J. Poulis, E. Robens, C. Massen, and G. Reichenauer
Jntti introduced a method to calculate the adsorption equilibrium by measuring the actual adsorbed amount three times after
a change to the gas pressure. By this method the experimental time for adsorption measurement can be considerably shortened.
The procedure was developed for use in adsorption measurements where the adsorbed masses are directly measured with a balance.
In the present paper we will demonstrate that the method is particularly useful in volumetric (manometric) measurements.
Jäntti introduced a method to calculate the adsorption equilibrium by the measurement of the actual adsorbed amount at three times after a change of the gas pressure. He applied that method for gas/solid systems in which simple adsorption processes occur and for an infinite number of adsorption sites. In the present paper we discuss the case that the number of sites is decreasing with increasing coverage.
Authors:J. Poulis, E. Robens, C. Massen, and P. Staszczuk
Jntti published in 1970 a method to
obtain values of the sorption parameters at an early stage of gravimetric
sorption measurements. In the present paper we apply that method to volumetric
sorption measurements to discuss its applicability. A method is presented
to cope with inaccuracies when using Jntti’s method. This will
be of special importance for volumetric measurements where accuracy plays
a major part. In the paper a second order regression method is used. We use
a computer simulation as well as experimental data on desorption of nitrogen
from a silica aerogel at 77 K.
Authors:J. Poulis, E. Robens, C. Massen, and M. Barczak
introduced a method to calculate the final value of the adsorbed mass already
in a very early stage of adsorption measurements. His method was restricted
to gravimetric measurements and to adsorptions, which satisfy the simplest
molecular model. One of the advantages of his method was that when more complicated
molecular models were necessary, the curve resulting from Jntti`s calculations
showed discrepancies from the curve predicted for the simple situation. We
used such deviations to evaluate the parameters of the models necessary for
the explanation of the measurements. One of the examples we discussed concerned
the influence of the occurrence of two parallel and simultaneous adsorptions.
In the present paper we discuss the application of these results to
adsorption onto a surface where roughness could be expected to play a part.
If we consider a rough surface as the sum of two extra surfaces we can apply
Jntti’s method by using our former results of parallel adsorption.
We characterise roughness by two parameters which we evaluated with Jntti’s
method. We emphasise that the existence of roughness is not demonstrated by
Jntti’s method, but that the method is useful for the evaluation
of parameters introduced by other arguments or from other sources.
Jntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure
change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present
paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive
and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process
is based on more than one adsorption mechanism or not.
Authors:Christoph Berthold, Volker Presser, Nadja Huber, and Klaus G. Nickel
times of only 10 s per XRD pattern. With the current setup even fastermeasurements (3 s or less), are possible, too.
In particular, the dehydration process of gypsum (CaSO 4 ·2H 2 O) to anhydrite (CaSO 4 ) in the temperature range from room
Authors:E. Kamseu, B. Ceron, H. Tobias, E. Leonelli, M. C. Bignozzi, A. Muscio, and A. Libbra
and experimental procedure. It is generally accepted that the most reliable values of λ are obtained by measuring in steady state conditions (transient methods allow somewhat fastermeasurement). The steady state techniques most commonly used for