József Kónya

Physical and chemical formations of lead contaminants in clay and sediment

A possible sink for divalent lead in the environment is clays such as montmorillonite that have cation exchange capacities. To assess the reaction, a calcium-montmorillonite was mixed with lead perchlorate solutions of varying concentrations and at various pHs. The recovered solids were studied by a variety of techniques (X-ray photoelectron and infrared spectroscopy, scanning electron microscopy, and atomic force microscopy) to determine what, if any, alterations occurred. The ion exchange of lead for calcium reduced the hydrated water in the clay, and evidence for proton-lead ion exchange at the edges of the sheets was observed. Evidence for a second, unexpected, reaction was also observed. Small spots (0.2 to 1 microm) of lead enrichment were observed on the surface of clay particles. They were also observed on clays recovered from the sediment of a Hungarian lake. The results show that lead ions are adsorbed onto montmorillonite by two processes: cation exchange and nano- and microparticle production. Cation exchange leads to the even distribution of the ions, while the production of spots causes the enrichment of lead ions. The production of these particles is not expected from the thermodynamic properties of the solution and cannot be observed in the absence of clay.

Interfacial chemistry of rocks and soils.

Components of Soil and Rock - Solution Systems Solid: Soil and Rock Liquid: Soil and Groundwater Solutions Interface of Rock/Soil - Aqueous Solutions References Interfacial Processes in Geological Systems: Studies on Montmorillonite Model Substance Use of Montmorillonite as a Model Substance: The Important Interfacial Processes on Montmorillonite Cation Exchange: Outer Sphere Complexation Synthesis and Characterization of Cation Exchanged Montmorillonites Surface Acid-Base Properties of Montmorillonite Ion Adsorption on the External Surfaces Separation of Interfacial Processes of Montmorillonite Role of Hydrogen Ions in the Interfacial and Dissolution Processes of Montmorillonite Effect of Complexation Agents Sorption of Organic Matter on Minerals Transformations Initiated by Interfacial Processes of Montmorillonite References Interfacial Reactions at Rock and Soil Interfaces Relationship Between Interfacial Properties and Geological Origin of Bentonite Clay Migration of Water Soluble Substances in Rocks Interfacial Acid-Base Properties of Soils Sorption of Cyanide Anion on Soil and Sediment References Experimental Methods in Studying Interfacial Processes of Rocks and Soils Analysis of the Solid Phase Analysis of the Liquid Phase Study of Interfaces References

Incorporation of Fe in the interlayer of Na-bentonite via treatment with FeCl3 in acetone

The effect of FeCl3 in acetonic medium on the structure of Na-bentonite was studied using X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, X-ray fluorescence spectroscopy and infrared spectroscopy to describe the structure of the bentonite before and after treatment. In the samples treated with FeCl3, an increase in the basal spacing was found by XRD, while a new magnetically split component assigned to Fe3+ incorporated within the interlayer regions of montmorillonite showed up in the low-temperature Mössbauer spectra. The Mössbauer parameters observed were close to those of Fe oxyhydroxides, suggesting the presence of some kind of nanoparticles. These results show that the treatment with acetonic FeCl3 solution is an effective method for introducing Fe into montmorillonite in the form of Fe3+ accommodated in the interlayer region. The treated samples proved to be efficient Lewis catalysts in the acylation of aldehydes (benzaldehyde and 4-OH-benzaldehyde) by acetic acid anhydride.

Cesium Ion Uptake by Moss (Hypnum cupressiforme)

Lower land mosses uptake water and minerals from the atmosphere. They can collect metals polluting the air and radioactive fallout elements so they can be suitable for monitoring of these substances. Cesium ion uptake by Hypnum cupressiforme is studied by a radioactive tracer, 134Cs. The quantity of cesium ion in different cellular locations and the capacity of ion uptake is determined. The total capacity is found to be several times 10−3 mol g−1 and is therefore of the same order of magnitude as the cation exchange capacity of ion exchangers. The kinetics and reversibility of the process is studied as well.

Lead accumulation on montmorillonite

The structure of lead and calcium-lead montmorillonites was studied by IR spectroscopy and scanning electron microscopy. The IR spectra showed no structural changes of the montmorillonite crystal lattice during calcium-lead cation exchange, only the intensities of hydrate water of the interlayer cation vary and the OH band on the edges disappears. Scanning electron microscopic studies showed that the distribution of lead is fairly even on the major part of the surface; however, there are places where the concentration of lead is higher than the mean surface concentration. The diameter of them is less than 1 µm. Similar lead enrichments were found on a natural clay sediment of a lake in Hungary. Lead ions adsorb on montmorillonite by cation exchange in the interlayer space and a heterogeneous nucleation on the particle surface followed by crystal growth.

Ion exchange isotherms in solid: electrolyte solution systems

It is shown show that the ion exchange isotherms and the law of mass action are equivalent, the c/a versus c functions can be derived from the law of mass action (c and a: the concentration of ions in ion exchanger and solution, respectively). The equations are applied for cation exchange processes of bentonite clay (cobalt, manganese, mercury ions with calcium-bentonite; strontium ions with sodium-bentonite; cesium ions with lanthanide bentonite; lutetium ion with calcium-bentonite). The linear or non-linear shape of the isotherms does not prove the heterogeneity of the ion exchanger or the interaction among the sorbed cations.

Chloride ion migration in natural bentonite

The disposal of nuclear wastes in geological formations demands the construction of engineering barriers. Bentonite clay rock is frequently used both as natural and engineering barrier. The natural bentonite rock in its original form is considered as compacted bentonite if the density is higher than 1.2xa0g/cm3. In this paper, the risk of the extrapolation of the laboratory experiments to field conditions and the high differences of the natural samples are emphasized: as much as 52xa0% standard deviation was obtained in the migration coefficients characterizing bentonite samples collected from the same site with a very small extent of sampling. Moreover, the bulk densities (1.18–1.87xa0g/cm3) and montmorillonite content are also rather different (45–71xa0m/mxa0%).The contradictions of the effects of the swelling clay mineral (montmorillonite) content and the bulk density of bentonite are illustrated: it is shown that the migration rate of chloride anion is determined by the ratio of the different water types (interlayer water of montmorillonite to free pore water of bentonite, including the electric double layer water). The apparent migration coefficients of bentonite clay and concrete (natural and artificial engineering barrier) are compared.

Long Term Effects of Cyanide Pollution of the River Tisza

The largest environmental pollution in the past few years was the cyanide pollution coming from mines of non-ferrous metals in Romania polluting the rivers Tisza and Szamos in the beginning of 2000. In addition to the direct damage at the time of pollution, there arises the question whether cyanide adsorbs in the settling of the river or in the surrounding soil. If it adsorbs, then it can reappear in the river water or in the soil solution, then from there getting to the source of drinking water it can have long-lasting effects. Therefore our aim was to determine whether the cyanide ion can adsorb in the settling of river Tisza, or in the soil near the shore as free cyanide ion or in the presence of Zn- and Cu ion coming together with cyanide pollution.