Research activities of the Colloid Chemistry Group
- Investigation of the dendrimers in aqueous solutions. Proton and metal complexes, interaction with small molecules. Catalytic processes. Diffusion in solutions.
- Synthesis and structural characterization of polyelectrolitytes (poly-g-glutamic acid and it’s derivatives, poly-acrylic acid). Proton and metal complexes. Size determination using various methods. Application as catalysts or flocculents.
- Examination of gels, emulsions and porous materials. Characterisation using NMR spectroscopy, light scattering, adsorption and other techniques.
Research activities of the Isotope Group
At the time of foundation of the Laboratory, the physico-chemical properties of carrier-free radioisotopes and their separation was the basic field of research. Certain environmental aspects, in particular the diffusion and sorption of radon were already investigated to some extent. The recent projects are based on these field. A significant improvement was the transfer from the artificial systems to the interactions of natural inorganic crystals and electrolyte solutions. The topic is indeed very broad and covers many projects which study interfacial processes in heterogeneous systems. Radiotracer techniques have been widely applied to investigate ion exchange and adsorption in soils, in particular on clay minerals. The chemical elements studied include many of those important either from nutritional or from environmental point of view. A new direction in this topic is associated with the problems related to the storage of low and medium level nuclear wastes. The sorption and migration of long lived fission products have recently been investigated in natural water/rock systems.
The main directions of research is the study of interfacial reaction of clay minerals, namely the adsorption and transformation of cation on the surface, the production of cation exchanged montmorillonite, the effect of organic substances on the sorption of cations, catalytic reactions on clay minerals.
The results of the theoretical research are used for the solution of practical problems as well. The applications of bentonite at Sajóbábony site have recently been studied. The interactions between radioactive isotopes and rocks, soils are studied, concerning the underground storage of nuclear wastes Our favorite research fields are as follows:
1. Interactions of metal ions, clay minerals and soils, the decontamination of soils
The interaction of metal ion and clay minerals/soils has been studied for a long time. The following systems have been examined:
Solid: soils, inorganic ion exchangers, clay minerals
Macro cations: Na+, K+, Mg2+, Ca2+
Micro cations: Zn2+, Mn2+, Cu2+, Fe3+, Co2+
Radioactive fallout: 134,137Cs+, 90Sr2+, 140Ba2+, 60Co2+, 45Ca2+, 63Ni2+, 36Cl–, 125I–, 99mTcO4–, 3H2O, 14CO32-
Polluting ions: Pb2+, Cd2+, Hg2+, Ag+
Catalysts: H+, Zn2+, Cu2+, Mn(II,IV), Ce(III,IV), Pd(0,II)
In addition the effect of H+ ion on the cation adsorption reaction has been studied as a model of the acidification of soils. The adsorption of PO43- and cianide anions on soil has also been investigated. The main analytical method has been the radioactive tracer method.
In the effect of complex forming agent on the cation adsorption reaction has been studied, included natural (citrate, tartarate, amino acids) and artificial (EDTA, NTA, DTPA, etc.) agents. The processes has been evaluated by surface complexation models.
These studies can show the decontamination possibilities of soils from metal pollutants.
2. Interactions of clay minerals and organic substances
The adsorption of organic substances on clay minerals can take place by different ways or can cause catalytic reactions. The interaction of organic substance and clay minerals are possible under environmental conditions or can be used for environmental-friendly syntheses. In this lecture some examples of these processes are shown.
The adsorption of an amino acid (valine) is possible: 1. in the interlayer space, where valine is adsorbed as H2Val+, 2. the adsorption of valine on the protonated aluminol sites, and 3. the adsorption of positively charged complexes on the deprotonated –SiO– sites. The ratio of these adsorption ways depends on the exchangeable cation. The process 3, for example, is possible only if the exchangeable cation forms a stable positive complex with valine.
The simple synthesis of the 1,1-diacetates 2 from a variety of aromatic aldehydes 1 can be made using Zn-montmorillonite as a catalyst:
where R: 2-HOC6H4, 4-HOC6H4, 3-HOC6H4, 2,4-(HO)2C6H3, 3,4-(HO)2C6H3, 4-MeOC6H4, 4-BrC6H4, 4-O2NC6H4, R’: 2-AcOC6H4, 4-AcOC6H4, 3-AcOC6H4, 2,4-(AcO)2C6H3, 3,4-(AcO)2C6H3, 4-MeOC6H4, 4-BrC6H4, 4-O2NC6H4. The synthesis is made under weak conditions, without the application of polluting materials.
Another example of catalytic effect of montmorillonite is the reaction of ketones and
alcohols, for example in case of acetone and ethanol:
3. Adsorption and migration of radioactive isotopes in geological formations
It is known that nuclear power plants produce radioactive wastes in great quantity. On the basis of halflife and radioactivity they are classified as low, medium and high level These wastes must be stored for very long time for the interactions of radioactive isotopes with the structural materials of the reservoirs and geological formations around as well as their transport phenomena have to be studied.
The migration of the radioactive isotopes in the geological formations (in rocks, soils, etc.) depends on a lot of factors. From these factors we have mainly studied the sorption of the isotopes. The kinetics and equilibrium of the sorption have been studied in batch experiments, the distribution coefficients have been determined. The degree of the sorption of the isotopes usually depends on its chemical species. The results can be used in the models of migration.
4. Quantitative determination of weak beta isotopes with long life time in nuclear waste
Nuclear wastes can contain weak beta isotopes with long life time (e.g. Zr-93, Se-79, Pd-107). They can quantitatively be determined with extreme difficulties. These isotopes are measured from solution and solid after digestion as well. The disturbing isotopes are removed, then the desired isotopes are chemically separated.