II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-41
Sr 2+ and Ba 2+ ions are in form of strong compounds which are not removed by treatment by
HCl and are not exhibited on X-ray pattern. The assessment of acidic properties was carried
out by method of the potentiometric titration and IR- spectroscopy. The pK values of surface
functional groups of initial carbon as well as of carbon with adsorbed Ca 2+ , Sr 2+ and Ba 2+ ions
were determined from the pH-metric titration curves. There are on the surface of initial carbon
acidic groups only. Cathodic polarization leads to partial or total disappearance of acidic
surface groups and to appearance of basic surface groups with the different values lgK diss . The
obtained results can testify that acidic surface groups don’t take part in adsorption of Ca 2+ ,
Sr 2+ and Ba 2+ ions on cathodic polarized carbon KM-2. In addition, the insertion of the
background ions into carbon structure by cathodic polarization is not observed that is
confirmed by Auger spectra.
The sorption capacity of cathodic polarized carbon with respect to Rb + ions is 0.75 meq g -1 ,
and with respect to Cs + ions is 1.00 meq g -1 . The X-ray phase analysis data point to the fact
that the rubidium ions are on the polarized carbon surface in the form Rb 2 CO 3 and in the
compounds that have general formula RbC x , the latter have the loosened graphite lattice. The
intercalation of Rb + into space between the carbon layers are not excluded. The results of
elemental analysis of these carbon samples show that there are, expect for elements found in
initial carbon samples, rubidium ions only. The other ingredients of background solution are
not detected.
After water washing and treatment of carbon samples by hydrochloric acid, 23 % of adsorbed
rubidium ion amount are removed from the carbon surface. In SEM micrographs of the
activated carbon samples with adsorbed rubidium crystal substance, forming conglomerate,
can be seen. The conglomerate formation was observed on the X-ray patterns too.
About 46% of electrosorbed Cs + ions are removed by water washing and treatment by
hydrochloric acid. Elemental analysis of the carbon surface with sorbed cesium shows that on
these carbon samples there are background solution ions (K + ). It is possible that under optimal
conditions for the cesium electrosorption the electrosorption of K + ions takes place too. On
the X-ray patterns of such carbons the lines, which can not be uniquely related to one or
another chemical compound of cesium or potassium, are detected.
The data obtained in this work are usable for the further development of electrocatalysis and
adsorption theory.
Experiments were conducted by use of instrumentation of Analytical Centre for Collective
Use of Daghestan Scientific Centre of RAS.
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