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Utilization of Slovak bentonites in environmental protection
S. Andrejkovičová, P. Komadel, J. Madejová, M. Pentrák
Pollution of the environment by toxic pollutants is a serious problem of present days.
Bentonites are nano-sized materials utilized in isolating layers of waste dumps due to their
excellent sealing properties. Among different types of barriers geosynthetic clay liners
(GCLs) are often used to minimize contaminant transport from waste disposal sites. GCLs are
factory fabricated thin layers, where bentonite is incorporated between geotextiles or bonded
to a geomembrane. Bentonites are composed mainly of montmorillonite, the most common
mineral of the smectite group. Chemical composition of montmorillonite, its sorption and
swelling capacity and stability in acid or alkali solutions significantly affect the utilization of
bentonite. In Slovakia Al-rich bentonite from Jelšový Potok (JP) deposit and Fe-rich bentonite
from Lieskovec (L) deposit are extensively investigated for their application in environment
protection. Basic geotechnical properties such as liquid and plasticity limit, free swelling and
permeability coefficient were
determined to ascertain if
bentonite from Lieskovec can
be used for GCL applications.
The permeability coefficients
of the order of 10 -11 m.s -1
suggested possible suitability
of this bentonite for GCLs;
however, other geotechnical
properties provided insufficient
values. Therefore the blends of
L-bentonite and JP-bentonite
with ratios 65:35, 75:25, 85:15
were prepared and tested. After
natrification of the blends all
Scheme of geosynthetic clay liner with bentonite filler
geotechnical parameters markedly improved compared to L-bentonite. Properties of the
mixtures containing 65 mass % of Na-L and 35 mass % of Na-JP bentonite were above those
required for bentonites used in GCL for reliable protecting of the environment.
Interactions of acid or alkali solutions with bentonites can significantly affect their
properties and, consequently, theirutilization in GCLs. For example, acid attack on bentonites
results in gradual damage of montmorillonite layers and formation of a protonated amorphous
silica phase. The IR spectroscopy in the near region was found to be a simple, fast and very
powerful method to follow structural changes occurring upon clay minerals dissolution in
inorganic acids. The OH overtone band at 7312 cm -1 revealed the creation of the Si-OH
groups even in the mildly-treated samples of L-bentonite. Similar changes observed in the
NIR spectra of different clay minerals confirm that the mechanism of the clay minerals
dissolution in inorganic acids is the same regardless of the structural arrangement and
chemical composition of the mineral.
Further information: S. Andrejkovičová: slavka.andrejkovicova@savba.sk
1. Andrejkovičová S., Rocha F., Janotka I., Komadel P.: Geotext. Geomembranes 26, 436-445, 2008
2. Madejová J., Pentrák M., Pálková H., Komadel P.: Vib. Spectrosc. 49, 211–218, 2009
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