2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P17 bIOMODIFIED FORMS OF NATuRAL
ZEOLITE AND ThEIR ENVIRONMENTAL
APPLICATION
MáRIA REHáKOVáa , ľUBICA FORTUnOVáa , SILVIA
ČUVAnOVáb , LUCIA GABEROVác and MáRIA
KUŠnIEROVáb aFaculty of Science, P.J.Šafárik University, Moyzesova 11,
041 54 Košice, Slovac Republic,
bInstitute of Geotechnics, Slovak Academy of Sciences, Watsonova
45, 043 53 Košice, Slovac Republic,
cUniversité de Provence, Centre de Saint-Jérôme, Marseille,
France,
maria.rehakova@upjs.sk
Introduction
The increasing levels of heavy metals in the environment
represent a serious threat to human health, living resources,
and ecological systems. Mobile and soluble heavy metal species
are not biodegradable and tend to accumulate in living
organisms, causing various deseases and disorders. Amongst
various treatment methods, ion exchange and sorption seem
to be the most attractive in case those nontoxic, low cost zeolites
are used.
natural zeolite of clinoptilolite type (CT) from East
Slovakian deposit in nižný Hrabovec has been studied with
respect to its feasibility of application in environmental area
in combination with biotechnological methods.
This recent investigation presents a continuation of our
previous study 1,2 of the decrease of content of heavy metal
and other toxic compounds (polychlorinated biphenyls-PCB)
in plants growing on heavily contaminated soils in industrial
areas. natural zeolite as well as zeolitic fertilizers was used in
this study. The results of study of growing certain agricultural
plants in contaminated soils with varying dosages of natural
zeolite (CT), zeolitic fertilizer and standard nPK fertilizer
confirmed the favorable influence of both zeolite and the zeolite
based fertilizer. Analysis of plant material showed that
the lowest content of heavy metals (Zn, Cu, Pb, Cd and Cr)
as well as of PCB was found in plants grown in contaminated
soils with the application of CT. The content of heavy metals
and PCB was lower almost of a half in comparison with
plants grown on untreated contaminated soils 2 . Plants grown
in contaminated soils with the addition of zeolitic fertilizer
showed a somewhat higher content. natural clinoptilolite by
ion exchange of heavy metals and sorption of toxic substances
into its cavities and channels blocked their reception into
the plants.
The aim of the recent study is the enlarging of clinoptilolite
sorption surface by the effect of microorganisms and
obtaining more efficient results of its application in the process
of reducing the residual content of heavy metals and
other toxic compounds in industrial contaminated soils.
According to the literature 3–5 , certain species of microorganisms
have been found to absorb surprisingly large
quantities of heavy metals. The removal of heavy metals
s367
from municipal and industrial wastes by biological treatment
systems has continued to be of interest. Bacterial surfaces
have great affinity to sorb and precipitate metals resulting
in metal concentration on the surface. All microbes, which
expose negatively charged groups on their cell surface, have
the capacity to bind metal ions. Complexolysis is a process
corresponding to microbial formation of complexing and
chelating agents that solubilize metal ions. The microorganisms
are able to transform toxic compounds to less toxic.
Biosorption of copper (II) ions by Thiobacillus ferrooxidans
were studied and is shown to be an effective bacterial bioaccumulation
process 3 . Acidithiobacillus and Thiobacillus cultures
are used for biological reduction of chromium (VI)-containing
wastes 4 . The attention is paid also to the utilization of
combination of microorganisms and microporous materials
(active carbon, zeolite) to achieve better sorption properties
for adsorption of toxic compounds 5 .
Our recent study is aimed to biomodification of the
surface of natural zeolite of the clinoptilolite type using the
microorganisms Thiobacillus ferrooxidans. Studied are also
model forms of zeolites containing copper ions, and the influence
of microorganisms on the biosorption of these ions as
well as other changes connected with metabolic activity of
the microorganisms present. The main motivation of this
study is the remediation of soils contaminated with high concentrations
of the residual of heavy metals and other toxic
compounds.
Experimental
In order to study modified forms of natural zeolite, the
natural zeolite of clinoptilolite type (CT) was used from
the Eastern Slovakia deposit in nižný Hrabovec. Two various
granulometric classes were taken for the experiments:
fine-grained one of the particle size up to 200 μm, denoted
as CT1, and coarse-grained of the particle size 0.4–0.6 mm,
denoted as CT2. Both granulometric classes of clinoptilolite
was thermally activated at 100–110 o C for 1 hour. So prepared
zeolitic samples were used for the synthesis of copper
forms as well as for cultivation by microoganisms.
All chemical agents used at the synthesis of modified
copper forms of the natural clinoptilolite, at the analyses
and preparation of nutrition medium were analytical grade
(Merck and Fluka).
P r e p a r a t i o n o f C o p p e r F o r m s o f
n a t u r a l Z e o l i t e
Copper forms of natural clinoptilolite were prepared by
the reaction of fine- and coarse thermally activated fraction
of natural clinoptilolite by a reaction with CuSO 4 solution of
two concentrations: 0.1 and 1.0 mol dm –3 . By this way, both
copper forms, fine-grained denoted as CuCT1 and coarse-grained
one, denoted as CuCT2, were obtained in consequence
of an ionic-exchange mechanism. These heterogeneous mixtures
were after 2 hours of stirring decanted several times and
centrifuged in order to get rid of sulphate ions and then dried
for 1 hour at 100 °C.