Introduction
In the Republic of Moldova, 50% of groundwater is polluted by toxic compounds,
such as sulphides, fluorides, fluorine, nitrites, nitrates, ammonium ions, heavy metals
etc., and therefore this water does not meet the sanitary standards of drinking water.
The use of activated carbons and catalysts obtained on the basis of these carbonic
adsorbents for obtaining drinking water from groundwater has gained a lot of
popularity lately. The results obtained by the Laboratory of Ecological Chemistry of
the Institute of Chemistry of the Republic of Moldova showed that oxidized carbonic
adsorbents, further impregnated with transition metal ions, especially with divalent
copper, enhance the oxidation of sulphides to sulphates, sulphites and thiosulphates.
This allows avoiding the formation of colloidal sulphur, and the catalysts obtained
from activated carbons may be used longer in the process of obtaining drinking water
from groundwater.
This research also presents the results of studies on the removal of heavy metal ions
from groundwater, especially of bivalent iron and manganese. The paper as well
shows the results obtained during the study of processes of regeneration of exhausted
activated carbons, using usual thermal methods and microwaves.
Materials and methods
In this research we used industrial activated carbons, as well as carbons obtained in
pilot conditions from the local raw material. In order to establish the mechanisms of
pollutants oxidation were used such physical and physicochemical techniques, as the
mass spectrometry, FTIR, nitrogen adsorption in gas phase, atomic spectroscopy,
thermal analysis, chemiluminescence etc.
Results and conclusions
The results show that during the oxidation of sulphides using carbonic catalysts, this
pollutant is mainly oxidized to sulphate. This may be explained by the fact that during
the aeration process in aqueous medium, copper ions that are chemically bound to the
carboxyl groups of activated carbons form free radicals that can oxidize sulphides
from an oxidation degree of -2 to +6.
The processes of removal of sulphides from groundwater were performed in dynamic
conditions. It was found that upon the passing of approximately 1450 liters of water
through the column filled with the adsorbent modified with copper ions CAPrO36Cu,

the adsorption/oxidation threshold was not reached and hydrogen sulphide was not
found in the eluates.
The capacity of removing hydrogen sulphide from groundwater, performed under
dynamic conditions as a ratio of the adsorbent volume and the volume of water passed
through the column, equals to 1:58400 for the CAPrO36Cu adsorbent, i.e. one volume
of catalyst obtained from activated carbons can serve to obtain 58400 volumes of
drinking water from the groundwater polluted with sulphides.
The activated carbons exhausted during the obtaining of drinking water were further
regenerated using the usual thermal method and microwaves. The obtained results are
shown in Tables 1 and 2.
Table 1. Structural parameters of activated carbons

The analysis of results presented in Tables 1 and 2 show that the regeneration of
activated carbons using microwaves is more efficient.
Acknowledgments
The research leading to these results has received funding from the MSCA-RISE action; project
734641 NanoMed, within the H2020 Marie Skłodowska-Curie Research and Innovation Staff
Exchange Programme.