Authors:Sukanta Maity, S. Mishra, S. Bhalke, G. Pandit, V. Puranik, and H. Kushwaha
In case of ground (groundwater) contamination or contaminants release from the disposal modules (facilities) to the geo-environment,
the fate of contaminant transport is mainly governed by the parameter called distribution (partition) coefficient, Kd. It is a measure of sorption of contaminants to soils. For that the sorption of polonium in soil were carried out using laboratory
batch method in different soil samples collected from different places around Turamdih uranium mining site. The kinetics of
polonium sorption were also carried out at different time intervals which clearly indicates that sorption equilibrium for
polonium achieved at around 72 h. The Kd for polonium varies from 1,443 to 7,501.3 L/kg in soil samples. Chemical characterization of soil and ground water samples
were carried out to know the effect of various chemical parameters with distribution coefficient of polonium.
The influence of distribution coefficients on the separation factor of lithium isotopes was studied with Dowex 50W-X8, 200–400
mesh, ammonium form, strongly acidic cation exchanger by changing the pH and EDTA concentration of the eluent. It was found
that the larger the EDTA concentration in the buffer solution, the smaller the distribution coefficients were. The separation
factor was increased with decreasing EDTA concentration. The separation factor of lithium isotopes linearly increased up to
a distribution coefficient value of 30, and gradually increased above 30. The optimum value of distribution coefficient of
lithium to separate litihium isotopes was about 30. The distribution coefficient was increased with increasing pH, but the
separation factor of lithium isotopes has no relation with pH.6Li concentrated on the resin phase, and7Li in the solution phase.
The method of determining the homogeneous distribution coefficient by the partial crystallization procedure has been examined.
It has been found that in chemically very similar systems, such as FeSO4·7H2O as host and60Co as guest, the partial crystallization technique gives very reliable data. However, in the case of CoSO4·7H2O as host and copper tracer as guest, the distribution coefficient found by the partial crystallization procedure is much
lower than that obtained by the traditional method of complete equilibration. In this system the distribution coefficient
increases as the period of partial crystallization is lengthened. The probable explanation of this particular behaviour is
Distribution coefficients /Kd/ of lanthanide elements on layered hydrous titanium dioxide, H2Ti4O9.nH2O /where n=1.2–1.3/, have been determined as a function of the pH of the aqueous phase. The plots of 1g Kd vs. pH gave straight lines with slopes equal to +3 except for the data for heavier lanthanides, suggesting ideal ion-exchange equilibria between tervalent cations in the aqueous phase and hydrogen ions in the hydrous oxide. Mutual separations of La–Cs and La–Ba have been achieved on a column of this material on the basis of large differences in affinities between the metal ion pairs.
The behaviour of60Co in sea water and sediments typical of the Solway Firth has been investigated. The distribution coefficient,Kd, of60Co2+ in sediments was determined using the batch sorption method and theKd variation with aqueous phase composition, sediment type and pH has been studied. Adsorption of60Co by sediments was found to be highest in de-ionised water and lower in NaCl solution (31 salinity). Adsorption was lowest in natural sea water, where theKd range was 2,270 to 2,750. Variation ofKd with sediment grain size was observed. It was shown that60Co adsorption was strongly dependent on pH in de-ionised water, with less variation in NaCl solution. Variance of60CoKd values were lowest in sea water in the range pH 5–8 indicating a more conservative behaviour of60Co than previously recognised. Hence60Co dispersion will be predominantly govemed by tidal behaviour.
Distribution coefficients Kd for the sorption of Cs and Sr on mixtures of a clay mineral (Ca-saturated bentonite) and humic material (Ca-humate) have been measured and were compared with calculated values obtained from the Kd-values observed for the pure components. The concentration of Sr and Cs in the solution was varied between 1·10–6 and 0.01N and the distribution of the elements determined by using radioactive tracers. All experiments were carried out in pure water as well as in the presence of a supporting electrolyte (0.01N CaCl2). It was found that the differences between the observed and calculated Kd-values were, if present, always negative if Cs was sorbed, and positive if Sr was sorbed.
Computer-aided modeling has been very successful in the design of chelating ligands for the formation of selective metal complexes. We report herein preliminary efforts to extend the principles developed for ion-specific chelating ligands to the weaker, more diffuse electrostatic interactions between complex anions and dicationic sites of anion-exchange resins. We present formal- and partial-charge methodologies for determining calculated electrostatic affinity between plutonium(IV) hexanitrato dianions and free analogues of dicationic anion-exchange sites. Both approaches correlate well with empirically-determined distribution coefficients for our bifunctional pyridinium-based resins (0.65<r2<0.98). This quantitative structure activity relationship (QSAR) will be useful in the determination of which structural modifications within a select series of bifunctional resins are most likely to be advantageous. Ultimately, we hope to refine this methodology to allow the a priori determination of ion-exchange behavior for a broad class of materials.
Authors:N. Kamei-Ishikawa, S. Uchida, and K. Tagami
In this work, soil-soil solution distribution coefficients (Kd) of Sr and Cs were obtained for 112 Japanese agricultural soil samples (50 paddy soil and 62 upland soil samples) using batch
sorption test. The relationships between Sr-or Cs-Kd values and soil properties were discussed. Furthermore, the amount of Cs fixed in soil was estimated for 22 selected soil
samples using a sequential extraction method. Then, cross effects of some soil properties for Cs fixation were evaluated.
The relative lipophilicity of bioactive derivatives of 2-[1-(4-alkylpiperazinyl)]benzothiazoles, 2-[4-(1-alkyl)piperidinyl]benzothiazoles, 2-(
’-dimethyl-1,2-ethanediamino)benzothiazoles, and 2-1-(4-aminopiperidinyl)benzothiazoles has been determined by reversed-phase thin-layer chromatography.
values of these compounds were determined with acetone-buffer mobile phases and extrapolated to 100% aqueous conditions. The lipophilicity was also determined by using optimized structures of the investigated compounds based on quantum mechanical calculations of the chemical structures (HyperChem 7.0). The distribution coefficients of the examined compounds were determined by use of the calculated ‘correction for dissociation’ descriptor. A correction was made based on the dissociation constants of the compounds, which were determined spectrophotometrically. We present a method for calculation of partition coefficients for ionizable compounds at a given pH. This property can be useful in analysis of quantitative structure-activity relationships. The distribution coefficients and the actual partition coefficient (at pH 7.4) were calculated for benzothiazole derivatives and for other drugs with different structures. The validity of calculations was checked by comparison with available experimental partition and distribution coefficients.
Authors:Zidan Houmani, Amran Majid, Shahidan Radiman, and Zaharudin Ahmad
226Ra is a member of the 238U natural decay series and is one of the most important isotope to be determined among the naturally occurring nuclides in
environmental samples. In order to evaluate the radiation dose from 226Ra, it is important to know its mobility in different types of soils. The aim of the present study is to quantify the influence
of physico-chemical soil properties on 226Ra adsorption. The distribution coefficients (Kd-value) of 226Ra in Selangor soil series samples were measured in one core, at three depth levels to evaluate the adsorbability of 226Ra. The soil samples were spiked with 226Ra tracer and the activities of 226Ra in the separated phase from batch sorption test were measured by a low background but high efficiency well-type HPGe detector.
Several physico-chemical soil properties were also characterised for each soil samples. Pearson’s correlation and stepwise
multiple regression test were applied at the 0.05 level of significance throughout all analysis to determine the relationships
and influences between distribution coefficients (Kd-value) of 226Ra with physicochemical soil properties for the Selangor soil series. The observed Kd value was in the range of 50.55–172.28 mL g−1 (mean: 93.20 ± 46.99 mL g−1). The regression showed that the highest positive correlations were observed for organic matter (OM) and cation exchange
capacity (CEC) (r = 0.96**, 0.81**, respectively) with Kd-values. The results indicate that the stepwise multiple regression model incorporating the soil’s OM and CEC accounts for
98% of the variability in distribution coefficients of 226Ra.