Environmental Engineering Reference
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and some perturbed generated isotherms (also experimental ones) contain full
information about the assumed distribution (number of peaks, their location, area,
etc.). Moreover, it was shown that an increase of the smoothing (regularization,
the INTEG algorithm) parameter leads to a strong smoothness and disappearance
of some (reasonable for experimental studies) peaks on the distribution curve (i.e.,
the PSD shape changes from initial polymodal distribution to much flatter mono-
modal one).It should be pointed out that similar results were obtained by others.
In recent studies some systematic investigations of the influence of pore structure
and the adsorbate-adsorbate and adsorbate-adsorbent parameters on the pore size
distribution functions were performed. Thus, it was shown on the basis of experi-
mental and theoretical data that the change in the shape and behavior of the local
adsorption isotherm do not guarantee the differences between the evaluated PSDs
except the strictly microporous adsorbents. All the observations suggested that for
some parameters the larger pore diameters of the PSD function are, the smaller
changes in the value of average pore diameter were observed. Moreover, the in-
fluence of the energetic heterogeneity on the structural parameters and quantities
is rather insignificant; all calculations led to almost the same PSD curves and
this similarity was observed for the adsorbents of different origin and possessing
different pore structures. In conclusion, the following question arises: Why and
when the gap between peaks of the differential pore size distribution curves can
be related to the mechanism of the primary and secondary micropore filling? In
order to answer this question we will use the experimental data published by some
researchers showing the development of secondary porosity in a series of carbons.
These data will be described by applying the proposed previously the ASA algo-
rithm with the method of Nguyen and Do (ND). Next it will be shown that the
behavior of the experimental systems studied represents a specific case, which can
be, together with other systems, the subject of the proposed general analysis of the
behavior of PSD curves. Therefore, by using carbon samples with varying porous
structure it is possible to perform a systematic study of various situations related
to the shape of the PSD curves, that is, the intensity of the both peaks, their mutual
location and the vanishing of one of them. It is also possible to obtain the informa-
tion how far the bimodality of those distributions is retained and reconstructed.
Moreover, the problem in the similarity of the local adsorption isotherms gener-
ated for the range of pore widths corresponding to the gap between peaks will be
discussed way, that is, the PSD curves (J(Heff)) using the ASA algorithm and the
method proposed by Do and co-workers are calculated. It should be noted that 82
local isotherms generated for the same effective widths changing from 0.465 up
to 233.9 nm were used. Additional details of the preparation of carbons and the
procedure of the differential PSD calculations were given previously. Nearly all
distribution curves show the existence of the bimodal porous structure. The loca-
tion of the maximum of the first peak and its intensity are similar for all samples
studied and only some changes in the width of this peak are observed.
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