Active carbons have a distinguished ability for removing wide ranges of
compounds from gas, aqueous and organic phases. The high adsorptive capacity
of active carbons is due to the high density of surface functional groups, large
porosity and intense specific surface area. Surface modification of active
carbons by metals for better selectivity in catalytic activity is also an interesting
research area.
The aim of this work was to obtain modified active carbons with
manganese compounds and to study the relationship between the impregnation
used conditions (e.g., concentration of manganese solutions, thermal treatment,
time, atmosphere) on the manganese loading and porous texture of final
samples. Two active carbons with different surface chemistry have been used as
carbonaceous support, one with basic surface (pH 9.5) and other with acidic
surface (pH 4.0). The structural changes caused by modification were estimated
on the basis of nitrogen adsorption-desorption isotherms. Obtained results show
that depending on thermal treatment conditions samples synthesised from the
carbonaceous support with basic surface have an increase of BET surface area
by about 13-26%, and a significant increase of mesopore volume (by 2 times).
This effect can be explained by additional activation at 300 °C due to salts used
for impregnation. Modified samples, synthesised from the carbonaceous support
with acidic surface, are more stable to thermal treatment. The insignificant
reduction of BET surface area by about 5-10% is in good agreement with
obtaining yield of samples.
Acknowledgements
The present work was performed within Joint Moldova-Belarus Project “Metal supported
catalysts for water treatment: synthesis, properties and using” (Project Nos.
15.820.18.02.04/B and X15МЛД -021).