Interaction between iron(III)-diphosphate and iron(III)-triphosphate and Ca-form of a clayey meadow soil was followed over a period of three days using radiotracer technique and kinetic evaluation of the results performed.59Fe served to determine the quantity of iron,45Ca to measure the calcium, and phosphorus was measured spectrophotometrically. Approximately 80% of both iron chelates disappeared from the solution during the time of the experiment as a result of two well distinguishable reactions. One of them is a rapid interfacial process of about 10 minutes and the other is a slow reaction leading to the decomposition of iron(III)-polyphosphate chelates. The two processes could be separated using the Christiansen equation.
Interaction between FeEDTA and calcareous soils was followed over a period of four weeks using a radiotracer technique, and a kinetic evaluation of the results was performed.59Fe served to determine the quantity of iron,14C to assay for EDTA and45Ca to measure calcium. During the experiment, i. e. within four weeks in case of the chernozem soil 61% and in case of the clayey meadow soil 51% of the iron chelate dissapeared from the solution. The loss in soluble iron was partly due to a rapid sorption process of about an hour and partly due to the slow decomposition of FeEDTA to Fe(OH)3. The two processes could be separated using the Christiansen equation.
The adsorption kinetics of strontium ion was studied on seven natural clay samples with radioactive tracer method. The kinetic
curves were determined and the kinetic data were evaluated by forms of first-rate kinetic equations with different terms,
generally used for adsorption of ions of low concentration. The adsorption process was reduced to two steps. Film diffusion
and participle diffusion were found in the case of five samples. Gel diffusion, film diffusion and participle diffusion were
found in the case of the other two samples. The presence of significant amount of cristobalite can explain the gel phase in
these two samples. The rate coefficients of steps were calculated from the kinetic curves.
Authors:Zs. Szántó, L. Papp, J. Kónya, N. Nagy, and Zs. Lengyel
Studies were initiated to investigate the effect of the delivery mode of45Ca ions through guinea pig skin in vivo. Direct current (DC), pulsating current (PC) and a Bernard current form, the “courtes
periodes” current profile (CP) were applied with the same current density (0.16 mA/cm2) and for the same duration (30 minutes). The45Ca ions were delivered from a Ca-bentonite patch radiolabeled with45Ca (a natural mineral clay rich in calcium, 50 mgCa/g). The total quantity of applied bentonite was 1.5g×10 days=15g.45Ca was counted in different biological samples of the animals. The delivery of45Ca ions into the body (systemic effect) is the highest when CP current is applied (6.87±0.95·10−12g/samples). The local effect appears to be more effective in case of DC current mode (5.89±0.12·10−12g/0.5g bone). Total calcium measurements proved that the result of transdermal radiocalcium delivery is not only an ion exchange
process at the surface of the bone but a deposition of calcium ions into the hydroxiapatite matrix (the net calcium introduction,
which represent the difference between the total calcium into the treated bone and total calcium into untreated bone varied
from 15.52±2.42·10−3g/0.5g bone to 44.30±3.50·10−3g/0.5g bone). The results suggest that iontophoresis could be used to accumulate calcium into different target tissues using
the appropriate current system.
Authors:M. Földvári, P. Kovács-Pálffy, N. Nagy, and J. Kónya
Various cation-exchanged montmorillonites (Li+, Na+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Cu2+, Ag+, Cd2+, Hg2+, Al3+, Pb2+ and NH4+)
were prepared from calcium montmorillonite and their properties were studied by means of X-ray diffraction and thermal analysis.
The two methods give information on the cation exchange in the interlayer space only. X-ray diffraction studies at room temperature
are mainly suitable for estimation of the exchange of cations of different valencies. At 500C, when the structure is completely
collapsed, the d value of montmorillonite depends on the non-hydrated ionic radius of the interlayer cation, but the measurement
interval is limited for fine interpretation. The thermoanalytical method is suitable for a better distinction of different
exchangeable cations of higher hydration energy on the basis of the DTG or DDTG curve.
Authors:A. Szabo, A. Fonseca, L. P. Biro, Z. Konya, I. Kiricsi, A. Volodin, C. Van Hasendonck, and J. B.Nagy
Some recent results on
the synthesis of coiled carbon nanotubes (CNTs) are summarized. Several
supported catalysts can lead to the formation of coiled CNTs. Interestingly,
certain domains of the coil pitch and coil diameter are favoured, and two
“stability islands”are found in the 3D representation of the number of coiled
CNTs as a function of both coil pitch and coil diameter. It is emphasized that
these nanotubes are formed either by introducing pairs of five-membered ring -
seven-membered ring or by forming haeckelite structures. The coiled CNTs could
be used in nanocomposite reinforcement as well as special sensors based on
their remarkable mechanical and electrical properties.