The use of activated carbon sorbents in the water treatment technologies is
one of the most safe and effective methods of water treatment. Carbon materials,
obtained by chemical activation, have an important role in the immobilization of
heavy metal ions from aqueous solutions due to the fact, that different acidic
functional groups (carboxyl, phenolic, hydroxyl etc.) are producing on the
surface of adsorbents during the activation process [1, 2].
The purpose of this research was to study the surface chemistry of
activated carbon produced from plum stones (CAPr) and nut shells (CAN-7)
using the phosphoric acid as an activating agent. The quality indices (adsorption
of methylene blue and I2, humidity), the porous structure parameters (calculated
from nitrogen adsorption-desorption isotherms), the amount of total acidic
groups of the studied activated carbons were determined. Some of the obtained
results are given in the table.
Quality indices and porous structure parameters of activated carbons

In order to identify the functional groups on the surface of investigated
samples was used the Boehm method of titration with aqueous solutions of
NaHCO3, Na2CO3, NaOH and HCl. Analysis of the obtained results allows us to
notice the presence of a substantial amount of acidic functional groups for the
studied samples of activated carbons. Taking into account the fact that the
degree of sorption of heavy metal ions depends on the quantity and quality of
the acidic groups on the surface of adsorbent we can assume that the activated
carbons CAPr and CAN-7 will exhibit a high level of immobilization of heavy
metal ions and they can be used in the water treatment processes.
1. T. Lupaşcu. Activated carbon from vegetal raw materials. Monograph/ In Romanian
L.: ÎEP: Ştiinţa, Chişinău, 2004.
2. T. Lupaşcu,.Tehnologii moderne de obtinere a carbunilor activi si utilizarea lor pentru
protectia mediuluisi a sanatatii omului. Buletinul ASM, Seria ŞBCA, N 1 (2004) 170.