The use of carbon adsorbents is one of the most safe and effective methods of water
treatment [1]. Modified carbon materials have an important role in the immobilization of heavy
metal ions from aqueous solutions due to the fact that different functional groups: carboxyl,
phenolic, hydroxyl form on the surface of adsorbents during the oxidation process [2].
The purpose of this study was to investigate the surface chemistry of intact charcoal and
of charcoal oxidized under different conditions. Special tests were performed for the oxidation of
charcoal at room temperature and by cooling to -10 °C. Hydrogen peroxide was used as the
oxidizing agent. To identify functional groups on the surface of investigated charcoal samples
was used the Boehm method of titration with aqueous solutions of NaHCO3, Na2CO3, NaOH
and HCl. The results obtained are shown in the table.
Table 1: The quality and quantity of functional groups on the surface of intact charcoal and the
one oxidized with hydrogen peroxide

MS- intact charcoal; MOR- charcoal oxidized at cool; MOC-charcoal oxidized at room
temperature.
Analysis of the obtained results allows us to notice a substantial increase of acidic
functional groups for samples of oxidized charcoal as compared to intact charcoal and at the
same time, a decrease in alkaline groups. Given that the degree of retention of heavy metal ions
is directly proportional to the amount of acidic functional groups on the adsorbent surface, we
can assume that oxidized carbon materials will exhibit a higher level of immobilization of these
pollutants.
References:
[1] Lupaşcu, T. Activated carbon from vegetal raw materials. Monograph/ In Romanian L.: ÎEP:
Ştiinţa, Chişinău, 2004, 224 p.
[2] Lupaşcu, T. Tehnologii moderne de obtinere a carbunilor activi si utilizarea lor pentru
protectia mediului si a sanatatii omului. Buletinul ASM, Seria ŞBCA, 2004, nr 1, pp 170-
175.