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Study of oxygen groups at a porous carbon surface by a new fast intermittent thermodesorption technique
Ist Teil von
Carbon (New York), 2011-05, Vol.49 (6), p.2062-2073
Ort / Verlag
Elsevier Ltd
Erscheinungsjahr
2011
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
A threshold thermodesorption method, named fast Intermittent TPD (ITPD), was used to study the evolution of CO
2 and CO arising from the decomposition of oxygen groups at the surface of a porous carbon used in the wastewater treatment.
Applied to the as-received carbon, CO
2-ITPD provided clear evidence for six values of the apparent activation energy of oxygen group decomposition (
E
app
): 139, 168, 206, 237, 270 and 290
kJ
mol
−1. Corresponding apparent pre-exponential factors (
A
app
) were also determined. The data (
E
app
and
A
app
) derived from ITPD for the six desorption steps allowed a successful description of the complete TPD profile, considering a Gaussian narrow distribution of
E
app
for each step. CO-ITPD also showed the presence of six (possibly seven) distinguishable steps upon CO thermal desorption and further demonstrated the interest of the fast ITPD technique for studying carbon surface chemistry.
The TPD and ITPD profiles of the carbon treated with sodium hypochlorite showed: (i) a sharp increase in the amount of desorbed species, (ii) the prevailing presence of less stable oxygen groups, mainly carboxylic acids, giving rise to CO
2 desorption at low temperature, and (iii) the progressive merging of the desorption steps detectable at low temperature upon increasing surface density of oxygen groups.