Distribution coefficient

Chelating resin based on phthalic acid-formaldehyde-resorcinol (PFR) had been synthesized and characterized by FTIR and elemental analysis. The resin had been studied as chelating sorbent for several metal ions [Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ]. The ion exchange capacity order is Ni(II) > Zn(II) > Cu(II) > Cd(II) > Pb(II). The ion exchange capacity for Cu(II) was 0.9736 mmol/g of dry resin. The distribution coefficient (K d) for five metal ions were determined in tartaric acid at different pH and concentration. The quantitative separations achived on the column of the chelating resin include Pb(II)-Cd(II), Pb(II)-Zn(II), Cu(II)-Pb(II). The morphology of PFR resin had been examined by SEM and optical photograph. The thermodynamic parameters such as activation energy (E a), entropy (S*), enthalpy (H*) and free energy (G*) for degradation were calculated from TGA data. The resin exhibits better exchange capacities for transition metal ions than heavy metal ions. The more amorphous character is responsible for the higher exchange capacities for transition metal ions and also the stable chelates are formed with transition metal ion as compared to heavy metal ions with PFR resin.

Density increases in caustic-side solvent extraction (CSSX) solvent have been observed in separate experimental programs performed by different groups of researchers. Such changes indicate a change in chemical composition. Increased density adversely ...

The estimation of high flood quantiles requires the extrapolation of the probability distributions far beyond the usual sample length, involving high estimation uncertainties. The choice of the probability law, traditionally based on the hypothesis testing, is critical to this point. In this study the efficiency of different model selection criteria, seldom applied in flood frequency analysis, is investigated. The efficiency

Abstract-We assess the potential of using foraminiferal calcite as a paleoceanographic indicator of seawater V concentrations. Laboratory culture experiments show that living benthic and planktonic foraminifera incorporate V into their test in direct proportion to seawater concentrations. Distribution coefficients relative to the culture solution are D = 2.1 X 10m3 and 2.8 X 10m3 for G. calida and A. lobifera, respectively. We use a cleaning procedure that effectively removes most V-rich contaminant phases from foraminiferal calcite preserved in the fossil record including organic matter and Mn-Fe oxyhydroxides. MnC03 overgrowths cannot be eliminated. Since V is conservative in the ocean, forami-niferal calcite recently accreted and found in surface sediment samples should have the same V content if this tracer accurately reflects seawater concentrations. V/Ca values for the same species of foraminifera are constant for core-top samples collected above the foraminiferal lysocline in...

We report gas phase calculations on uranyl ions (UO 2 2+) complexes with symmetrical trialkyl phosphates, (RO) 3 PO, as ligand (L), where, R is a linear or branched propyl, butyl and amyl groups. Density functional theory (DFT) using double numerical polarization (DNP) basis set with restricted scalar relativistic effect is used to validate the structural features of UO 2 (NO 3) 2 L 2 complexes against experimental XRD data. The interaction energy and extraction ability of the trialkyl phosphates are compared for uranyl (VI) ion. Steric effect of the extracting agent that governs the metal extraction is explained in terms of cone angles made by ligands towards metal ion. The complexation behaviour of straight chain and branched chain ligands is well understood by this study. The relative order of cone angles and interaction energies from DFT simulation follow the trend with the experimentally determined distribution coeffi cients. An interesting approach of this work is the importance of cone angle in the solvent extraction.

The performance assessment of high level radioactive waste disposal has emphasized the role of colloids in the migration of radionuclides in the geosphere. Previous literature [Nagasaki S, Tanaka S, Suzuki A. Fast transport of colloidal particles through quartz-packed columns. J. Nucl. Sci. Technol. 1975;30(11):1136] indicates that owing to hydrodynamic chromatography the colloid velocity may not be equal to that of groundwater. Using hydrodynamic chromatography, this work investigates the effects of the size of colloidal particles on the radionuclide migration facilitated by colloids in a single fractured porous rock. Also, a methodology is proposed to develop a predictive model to assess transport within the fracture rock as well as various other phenomenological coefficients, particularly the size of colloidal particles. In addition, a fully developed concentration profile for non-reactive colloids in the fracture is developed to elucidate hydrodynamic chromatography of colloids in geological media. The external forces acting on colloidal particles hypothesized in the model proposed herein include inertial force, van der Waals attractive force, double layer force as well as gravitational force. The dispersion coefficient of colloids and the distribution coefficient for radionuclides with colloids are also considered as they pertain to the size of the colloid. In addition, the size distributions of colloids are utilized to investigate the effects of polydispersed colloids.

The performance assessment of high level radioactive waste disposal has emphasized the role of colloids in the migration of radionuclides in the geosphere. Previous literature [Nagasaki S, Tanaka S, Suzuki A. Fast transport of colloidal particles through quartz-packed columns. J. Nucl. Sci. Technol. 1975;30(11):1136] indicates that owing to hydrodynamic chromatography the colloid velocity may not be equal to that of groundwater. Using hydrodynamic chromatography, this work investigates the effects of the size of colloidal particles on the radionuclide migration facilitated by colloids in a single fractured porous rock. Also, a methodology is proposed to develop a predictive model to assess transport within the fracture rock as well as various other phenomenological coefficients, particularly the size of colloidal particles. In addition, a fully developed concentration profile for non-reactive colloids in the fracture is developed to elucidate hydrodynamic chromatography of colloids ...

Raoul Volcano occupies a simple oceanic subduction setting in the northern part of the Kermadec Arc on the Pacific-Australian convergent plate boundary. The primary inputs to the magmatic system that feeds the volcano are a subduction component derived from the subducting old Pacific oceanic lithosphere and its veneer of pelagic sediment, and the overlying peridotitic mantle wedge. Conservative trace elements that are very incompatible during mantle melting are relatively depleted in Raoul lavas indicating a source that has been depleted during an earlier melting event. Major element co-variations indicate magma genesis by 25% near fractional melting of a mantle source that is weakly depleted (2% melt extraction) relative to a fertile MORB source. An important influence on the composition of the mantle component is progressive melt extraction coupled with minimal advection of fresh material into the sub-arc zone followed by melt extraction from a melting column beneath the spreading centre of an adjacent back arc basin. High field strength element and rare earth element systematics indicate involvement of a subduction-related component of constant composition. Two fluid components can be distinguished, one enriched in large ion lithophile elements inferred to be an aqueous fluid that is continuously added to the ascending melt column and the other a less mobile fluid that transfers Th. A homogeneous subduction-related component of constant composition and magnitude * Manuscript Click here to view linked References arises if the slab-derived flux migrates from the slab-mantle interface to the sub-arc melting column by repeated episodes of amphibole formation and decomposition its composition is then governed by the distribution coefficients of pyroxene and its magnitude by the degree of amphibole saturation of mantle peridotite. The results from Raoul Volcano are comparable to those from other oceanic subduction-related arcs such as South Sandwich and Marianas suggesting that this is a general model for oceanic arcs.

Abstract The preparation of polystyrene-based titanium phosphate membranes at different pressures with varying amounts of material has been explained. The membrane potentials of inorganic membranes were measured with uni-univalent electrolytes (KCl, NaCl and ...

Liquid-liquid equilibria for the ternary system water + acetic acid + 1-pentanol were measured over a temperature range of (288 to 323) K. The results were used to estimate the interaction parameters between each of the three compounds for the NRTL and UNIQUAC models and between each of the main groups of H 2 O, CH 2 (paraffinic CH 2), OH, and COOH for the UNIFAC model as a function of temperature. The estimated interaction parameters were successfully used to predict the equilibrium compositions by the three models. The NRTL and UNIQUAC models were almost equally good in predicting the overall equilibrium compositions of the studied system. The UNIFAC model satisfactorily predicted the equilibrium compositions. On the basis of this work, the distribution coefficients were also calculated and compared with the experimental values.

An electrokinetic model is proposed to describe a slight drop deformation which is induced by a weak external electric field. The fluids forming the system are considered Newtonian incompressible dielectric liquids containing free electric charge carriers. According to the model, the charge carriers take part in migration, diffusion and convection transport and there is no solute adsorption at the interface. Thermodynamic quasi-equilibrium at the interface is assumed for the charge carriers in the contacting liquids. The interfacial thermodynamic equilibrium is described using a common distribution coefficient for all the carriers. The problem is simplified by assuming equal diffusion coefficients for the different charge carriers within the same liquid. An analytical expression is obtained for slight drop deformation which is proportional to the second power of the applied field strength magnitude. The expression derived represents the drop deformation as a function of the paramete...

Alkali feldspar partition coefficients for Fe, Rb, Ba, Sr, and Eu vary with melt peralkalinity due to changes in melt polymerization and to the systematic increase in X or and decrease in X an of the feldspar. In going from trachyte to pantellerite, Fe partition coefficients increase from ...

Reversed phase HPLC was used to assess the lipophilicity of a series pyrrolyl-acetic acid derivatives with aldose reductase inhibitory activity. The pH conditions were adjusted at 3.0 to investigate the behavior of the neutral species and at pH 7.4, at which the ionized form predominates, using phosphate and MOPS buffer. Retention was monitored in absence and in presence of different amounts of n-octanol in the mobile phase in order to explore the chromatographic conditions which best reproduce the octanol-water partition or distribution coefficients. The effect of n-octanol in retention was systematically studied and its role in lipophilicity assessment was evaluated. Nevertheless rather moderate regression equations were obtained, which deviated significantly from the ideal 1:1 correlation. No significant effect of buffer was observed. The appropriateness of retention factors to be used in correlation with aldose reductase inhibitory activity was further evaluated and compared to the efficiency of the corresponding octanol-water logP values.

We report trace element (Mg, Sr and Ba) records based on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from three coeval Holocene speleothems from Great Chamber in GB Cave, southwest England. The trace element records are placed on a common timescale on the basis of a suite of TIMS 230Th-234U ages. This permits assessment of the reproducibility of the trace element record in coeval speleothems. The trace element records are not coherent, raising dobuts over the reliability of individual trace element records as potential archives of palaeoenvironmental information. Mg/Sr in speleothem calcite has been proposed as a potential palaeothermometer as Mg partitioning into calcite from water is temperaturedependent, while Sr partitioning into calcite is temperature-independent. However, we present the results of calculations which demonstrate that the observed Mg/Sr values in the three stalagmites cannot have been produced by Holocene temperature changes alone and...

The aim of the present work is to obtain the separation of ~ 3 ffi Th from the radioisotopes formed in the irradiation of Mn, U, Ba, Cs, Co and the lanthanide elements with thermal neutrons, because they may interfere in the neutron activation analysis of Th, when the activity of : 33Th is used. The experiments were performed with the resin Bio-Rad AG 50W X-4 and X-8 (100-200 mesh) in the thorium form. The separation of 23~Th from the interfering radioisotopes is based on the retention of ffi s 3Th by the resin (isotope exchange) and the elution of the interfering radioisotopes with a dilute solution of Th in 0.5M HCL Batch experiments were made in order to determine the equilibrium time for the isotopic ion exchange of thorium and also the distn~oution coefficients of the interfe:ing elements between the solution and the resin. Column experiments were carried out with the purpose of establishing the conditions that allow the maximum isotope exchange of:33Th and the minimum retention of the interfering radioisotopes in the resin. With this purpose, a statistical interpretation of a four variable experimental design is presented.

The minimization of pentachlorophenol (PCP) transport in the environment driven by industrial wastewater discharges can be accomplished by sorption in natural, available and low cost by-products like pine bark. Taking into account that PCP is a chemical which behaviour is highly dominated by the surrounding features, this work intended to evaluate the sorption kinetics and equilibrium parameters according to the pH and temperature as well as the pine bark particle size. The PCP uptake by pine bark showed to be faster in the initial phase followed by a slower process, being 24 h the suitably time to reach the sorption equilibrium in the range of pH studied. The neutral PCP species showed to have higher binding capacity to pine bark than the anionic PCP, which was reflected in a decrease in the distribution coefficient (K d) of the linear sorption isotherm with the increase of solution pH from 2 to 7. On the other hand, between 10°C and 35°C, the temperature does not seem to play a significant role in the PCP sorption by pine bark, while the sorbent size is a key parameter to enhance the overall process.

The extraction of glycolic acid from an aqueous glycolonitrile hydrolysate with tri-n-octylamine (TOA) in diluents of 1-octanol and kerosene was investigated in this article. The influences of TOA concentration, extraction temperature and phase ratio, O/W (volume ratio of organic phase to aqueous phase) on the acid distribution coefficient and loading factor of TOA were measured. The liquid-liquid equilibrium data of glycolic acid distributed between the extract phase and the raffinate phase were determined, and correlated with a model developed from the mass action law and suitable assumptions. Additionally, the acid loaded extractants were regenerated by using pure water as the back-extractant. The results show that lower temperature is beneficial to the extraction of glycolic acid from the hydrolysate, while higher temperature and phase ratio (O/W) are favorable to the back-extraction.

In order to quantify possible fractionation of U and Pb into a metallic core, we have performed piston cylinder and multianvil press experiments at high pressure (up to 20 GPa) and high temperature (up to 2400°C) and obtained the distribution coefficient D metal-silicate and the exchange partition coefficient K metal-silicate for these elements between metal and silicates (mineral or liquid). D Pb metal-silicate and D U metal-silicate depend strongly on the S content of the metallic phase, and also on the oxygen fugacity, in agreement with an effective valence state of 4 for U in silicates and 2 for Pb in silicates. K Pb d metal-silicate and K U d metal-silicate show no discernable pressure and temperature trend. U remains lithophile even at high pressure and high temperature but its lithophile nature decreases at very low oxygen fugacity. From our experimental data, it was possible to calculate the U and Pb contents of the cores of Mars and Earth under core-mantle equilibrium conditions at high pressure and high temperature. From the D metal-silicate of the present study, we obtained that: 0.008 ppm < Pb in the core <4.4 ppm, and 0.0003 ppb < U in the core < 0.63 ppb, depending on whether the metal is S-free or S-saturated respectively, and if the mantle was molten or solid during the segregation process of the Earth's core around DIW-2. For Mars, based on a core segregation process around DIW-1, we obtained that: 0.005 ppm < Pb in the core < 3 ppm, and 0.00002 ppb < U in the core < 0.05 ppb, depending on the metallic composition: S-free or S-saturated respectively. Our results suggest that the low concentration of Pb in the terrestrial mantle could not be explained by an early Pb sequestration in the Earth's core even if S is the dominant light element of the core. If we assume a magma ocean scenario, U might produced a maximum value of 1.5% of the total heat budget of the core with a segregation occurring below DIW-3. The values found in the present study for U in the Martian core suggest that the magnetic field activity of Mars before $0.5 b.y. after its formation would be difficult to ascribe to the decay of U alone.

A forced-gradient test of solute transport was conducted adjacent to the site of a p•evious natural gradient test to allow comparison of results obtained from the two types of field tests. In the forced-gradient test, one inorganic tracer and four organic solutes (carbon tetrachloride, trichloroethylene, tetrachloroethylene, and hexachlomethane) were injected for 48 hours. The migration of the dissolved chemicals toward the extraction well was monitored by multilevel samplers and a partially penetrating monitoring well. Moment analyses of the solute breakthrough curves at the multilevel points provide model-independent insight into the variation of hydraulic conductivity and organic solute retardation in the aquifer. The estimated retardation factors fall within the range estimated in the previous natural gradient test. Sorption distribution coefficients inferred from the transport data indicate spatial variability of sorption for all solutes, with mean values and ranges similar to those observed in laboratory studies of core or bulk samples. Some evidence was obtained for spatially variable in situ transformation of hexachloroethane. R = vw/Vc (1) If the aquifer is uniform and sorption is linear, reversible, and instantaneous, the retardation factor for a contaminant migrating through the aquifer will be constant and may be expressed as follows:

Liquid–liquid equilibrium (LLE) data of water+acetic acid+dimethyl succinate were measured at 298.2, 308.2, and 318.2K. Complete phase diagrams were obtained by determining binodal curves and tie lines. The reliability of the experimental tie line data was confirmed by using the Othmer–Tobias correlation. The UNIFAC and modified UNIFAC model were used to predict the phase equilibrium data in the ternary system. Distribution coefficients and separation factors were evaluated for the immiscibility region.

Yucca Mountain is the U.S. Department of Energy's potential geologic repository designed to store and dispose of commercial spent nuclear fuel, defense high level waste glass, and other high-level radioactive waste forms. If approved, the site would be the nation's first geological repository for disposal of this type of radioactive waste. Yucca Mountain is located on federal land adjacent to the Nevada Test Site in Nye County, Nevada. It is approximately 100 miles northwest of Las Vegas, Nevada. Colloids may have the potential to transport strongly sorbing radionuclide contaminants in soils and groundwater aquifers (McCarthy and Zachara 1989). Recent studies from the Nevada Test Site, a site with a similar geology to Yucca Mountain, have indicated the enhanced mobility of plutonium in the saturated zone, albeit in minute quantities, in association with various silicate minerals (Kersting et al. 1999). The observed association of plutonium with silicate colloids by Kersting et al. (1999), sorption experiments by Lu et al. (2000), and waste form corrosion tests (Bates et al. 1992) indicate that the attachment of plutonium to colloids may be an irreversible process. However, current Yucca Mountain models that assume irreversible sorption of plutonium, americium, and thorium onto colloids have led to highly conservative scenarios. This is partly because of the K d ranges used as well as the total surface area assumed to be available for uptake. Nevertheless, a slowly reversible term may provide more realistic predictions for radionuclide transport in the proposed repository. This report considers a sorption model containing the minimal dynamic features of the system to fit plutonium adsorption data similar to that developed by Painter et al. (2002). Global fits to recent data favored nonzero values of reversible sorption, allowing the definition of equilibrium distribution coefficients in all cases except the synthetic form of montmorillonite. In most cases, the two-site model was adequate to fit the data. The model represents a mathematic simplification of the time-dependent sorption process and takes no account for pH-dependent surface charge changes and actinide-mineral surface interfacial chemistry. However, this allows the model to be readily incorporated into existing performance assessment codes when applied to repository environment relevant data sets.

Bisphenol A (BPA; 2,2-(4,4 0-dihydroxydiphenyl)propane) is predominantly used as an intermediate in the production of polycarbonate plastics and epoxy resins. Traces of BPA released into the environment can reach the soil via application of sewage sludge from wastewater treatment systems that receive wastewaters containing BPA, or from leachate from uncontrolled landfills. The biodegradability of BPA has been previously investigated in several studies designed to simulate surface waters and biological wastewater treatment systems. However, there is little information available about the fate of BPA in soil. Therefore, laboratory soil degradation and batch adsorption studies were conducted with 14 C-BPA and four soils according to international guidelines. The soils represented a broad range of physico-chemical properties. An important result of the degradation study was that, independent of the soil type, 14 C-BPA was rapidly dissipated and not detectable in soil extracts following 3 days of incubation. Based on this result, a dissipation half-life of less than 3 days was estimated. The major route of dissipation of 14 C-BPA in soil was the formation of bound residues that could not be recovered by exhaustive Soxhlet extraction. 14 C-BPA was also shown to be transiently converted to up to five metabolites, but within 3 days, neither 14 C-BPA nor 14 C-metabolites were detectable in the soils. After 120 days incubation, significant amounts (up to 20% of the radioactivity applied) of the parent compound were recovered as 14 CO 2. Soil adsorption experiments indicated that the distribution coefficients (K oc) were between 636 and 931, classifying BPA as having low mobility for all tested soils. From the results of this study, it was concluded that if BPA reaches the soil compartment, it is not expected to be stable, mobile, or bioavailable.

In modelling the fate and transport of heavy metals, the sorption processes, through the distribution coecient, are applied to determine the amount of sorbed and dissolved fractions. Usually, these distribution coecients are assumed to depend only on suspended sediment interactions. In estuaries, however, observations indicate that dissolved concentrations increase with salinity. It is hypothesized that salt competes for binding sites, leading to lower distribution coecients. To study the fate and transport of heavy metals in an estuarine environment, a two-dimensional ®nite volume, depth-averaged toxic transport model has been developed. The distribution coecients are approximated as a function of sodium activity or salt concentration. Other model parameters are obtained from a recently developed hydrodynamic model, salt transport and cohesive sediment transport modules. The model has been applied to the Scheldt Estuary and the results for both sorbed and dissolved heavy metal concentrations agree fairly well with measured data, indicating that under estuarine mixing, salt concentration is an important factor aecting the fate and transport of heavy metals.

The minimization of pentachlorophenol (PCP) transport in the environment driven by industrial wastewater discharges can be accomplished by sorption in natural, available and low cost by-products like pine bark. Taking into account that PCP is a chemical which behaviour is highly dominated by the surrounding features, this work intended to evaluate the sorption kinetics and equilibrium parameters according to the pH and temperature as well as the pine bark particle size. The PCP uptake by pine bark showed to be faster in the initial phase followed by a slower process, being 24 h the suitably time to reach the sorption equilibrium in the range of pH studied. The neutral PCP species showed to have higher binding capacity to pine bark than the anionic PCP, which was reflected in a decrease in the distribution coefficient (K d) of the linear sorption isotherm with the increase of solution pH from 2 to 7. On the other hand, between 10°C and 35°C, the temperature does not seem to play a significant role in the PCP sorption by pine bark, while the sorbent size is a key parameter to enhance the overall process.

To improve general understanding of biochemical mechanisms in the field of uranium toxicology, the identification of protein targets needs to be intensified. Immobilized metal affinity chromatography (IMAC) has been widely developed as a powerful tool for capturing metal binding proteins from biological extracts. However uranyl cations (UO 2 2+) have particular physico-chemical characteristics which prevent them from being immobilized on classical metal chelating supports. We report here on the first development of an immobilized uranyl affinity chromatography method, based on the cation-exchange properties of aminophosphonate groups for uranyl binding. The cation distribution coefficient and loading capacity on the support were determined. Then the stability of the uranyl-bonded phase under our chromatographic conditions was optimized to promote affinity mechanisms. The successful enrichment of uranyl binding proteins from human serum was then proven using proteomic and mass spectral analysis.

As a prerequisite for most evaluations of radionuclide transport pathways in marine systems, it is necessary to obtain basic information on the sorption potential of contaminants onto particulate matter. Kd values for use in modeling radionuclide dispersion in the Kara Sea have been determined as part of several international programs addressing the problem of radioactive debris residing in Arctic Seas. Field and laboratory Kd experiments were conducted for the following radionuclides associated with nuclear waste: americium, europium, plutonium, cobalt, cesium and strontium. Emphasis has been placed on two regions in the Kara Sea: (i) the Novaya Zemlya Trough (NZT) and (ii) the mixing zones of the Ob and Yenisey Rivers (RMZ). Short-term batch Kd experiments were performed at-sea on ambient water column samples and on samples prepared both at-sea and in the laboratory by mixing filtered bottom water with small amounts of surficial bottom sediments (particle concentrations in samples = 1-30 mg/l). Within both regions, Kd values for individual radionuclides vary over two to three orders of magnitude. The relative particle affinities for radionuclides in the two regions are americium approximately equal to europium &amp;gt; plutonium &amp;gt; cobalt &amp;gt; cesium &amp;gt; strontium. The values determined in this study agree with minimum values given in the IAEA Technical Report [IAEA, 1985. Sediment Kd&amp;#39;s and Concentration Factors for Radionuclides in the Marine Environment. Technical Report No. 247. International Atomic Energy Agency, Vienna.]. Given the importance of Kd&amp;#39;s in assessments of critical transport pathways for radionuclide contaminants, we recommend that Kd ranges of values for specific elements rather than single mean values be incorporated into model simulations of radionuclide dispersion.

Kinetic rates of Fe 2 +-Mg disordering in three orthopyroxenes (mean value of XF~ = Fe 2 +/(Fe 2 + + Mg) = 0.175, 0.482, 0.770 respectively) have been determined employing heating experiments and single crystal X-ray structural refinements. Disordering rate constants (/{) (550-800 ~ C) for two pyroxenes are given by: In/(= 27.107(• 5.177)-32062(+ 783) T-I(XFe = 0.175) In/~ = 16.142(___ 0.057)-18 227(___ 423) r-1 (XFo = 0.770) The distribution coefficients KD (representing a steady state of disordering Fe~2 + MgM1-~FeM1 + MgM2) are given by: in KD = 5.016(• 0.223)-7033 (_+ 1473) T-1 (XFe =0.175) In KD = 1.988 (• 0.122)-3809 (_+ 913) T-1 (XFe = 0.770) These distribution coefficients provide the constraint of the disordering reaction on the value of the equilibrium constant for Fe 2 +-Mg order-disorder. Until the low temperature dependence of KD is well constrained, the calculation of cooling rates of pyroxenes and host rocks cannot be done reliably.

The present study involves the screening of silver nanoparticles containing carbonized yeast cells isolated from coconut cell sap for efficient adsorption of few long lived radionuclides like 137 Cs 55 , 60 Co 27 , 106 Ru 44 , 239 Pu 94 and 241 Am 95. Yeast cells containing silver nanoparticles produced through biological reduction were subjected to carbonization (400°C for 1 h) at atmospheric conditions and their properties were analyzed using fourier transform infra-red spectroscopy, X-ray diffraction, scanning electron microscope attached with energy dispersive spectroscopy and transmission electron microscope. The average size of the silver nanoparticles present on the surface of the carbonized silver containing yeast cells (CSY) was 19 ± 9 nm. The carbonized control yeast cells without silver exposure (CCY) did not contain any particles on its surface. The efficiency of CSY and CCY towards the radionuclide adsorption was studied in batch mode at fixed contact time, concentration, and at its native pH. CSY was efficient in removal of 239 Pu 94 (76.75%) and 106 Ru 44 (54.73%) whereas CCY showed efficient removal only for 241 Am 95 (62.89%). Both the adsorbents did not show any retention with respect to 60 Co 27 and 137 Cs 55. Based on the experimental data, decontamination factor and distribution coefficient (K d) were calculated and, from the values, it was observed that these adsorbents have greater potential to adsorb radionuclides.

... RF resin column to specifically remove 137 Cs and residual 90 Sr from the waste (55. Yeotikar , RG ; Kaushik , CP ; Johnson ... Kannan , N. ; Sundaram , MM ( 2001 ) Kinetics and mechanism of removal of methylene blue by adsorption on various carbons—a comparative study . ...

In order to quantify possible fractionation of U and Pb into a metallic core, we have performed piston cylinder and multianvil press experiments at high pressure (up to 20 GPa) and high temperature (up to 2400°C) and obtained the distribution coefficient D metal-silicate and the exchange partition coefficient K metal-silicate for these elements between metal and silicates (mineral or liquid). D Pb metal-silicate and D U metal-silicate depend strongly on the S content of the metallic phase, and also on the oxygen fugacity, in agreement with an effective valence state of 4 for U in silicates and 2 for Pb in silicates. K Pb d metal-silicate and K U d metal-silicate show no discernable pressure and temperature trend. U remains lithophile even at high pressure and high temperature but its lithophile nature decreases at very low oxygen fugacity. From our experimental data, it was possible to calculate the U and Pb contents of the cores of Mars and Earth under core-mantle equilibrium conditions at high pressure and high temperature. From the D metal-silicate of the present study, we obtained that: 0.008 ppm < Pb in the core <4.4 ppm, and 0.0003 ppb < U in the core < 0.63 ppb, depending on whether the metal is S-free or S-saturated respectively, and if the mantle was molten or solid during the segregation process of the Earth's core around DIW-2. For Mars, based on a core segregation process around DIW-1, we obtained that: 0.005 ppm < Pb in the core < 3 ppm, and 0.00002 ppb < U in the core < 0.05 ppb, depending on the metallic composition: S-free or S-saturated respectively. Our results suggest that the low concentration of Pb in the terrestrial mantle could not be explained by an early Pb sequestration in the Earth's core even if S is the dominant light element of the core. If we assume a magma ocean scenario, U might produced a maximum value of 1.5% of the total heat budget of the core with a segregation occurring below DIW-3. The values found in the present study for U in the Martian core suggest that the magnetic field activity of Mars before $0.5 b.y. after its formation would be difficult to ascribe to the decay of U alone.

Measurements of interfacial tensions for 2-ethyl-hexanol-(propylene oxide)∼ 4.5-(ethylene oxide)∼ 8 (2EH-PO 4.5-EO 8) at the planar water-CO 2 interface and the surfactant distribution coefficient are utilized to explain microemulsion and macroemulsion phase behavior from 24 to 60 • C and 6.9 to 27.6 MPa. A CO 2 captive bubble technique has been developed to measure the interfacial tension at a known surfactant concentration in the aqueous phase, with rapid equilibration at the water-CO 2 interface. The surface pressure (o −) decreases modestly with density at constant temperature as CO 2 solvates the surfactant tails more effectively, but changes little with temperature at constant density. The area per surfactant at the CO 2-water interface determined from the Gibbs adsorption equation decreases from 250 A 2 /molecule at 24 • C and 6.9 MPa, to 200 A 2 /molecule at 27.6 MPa. It was approximately twofold larger than that at the water-air interface, given the much smaller o driving force for surfactant adsorption. For systems with added NaCl, decreases with salinity at low CO 2 densities as the surfactant partitions from water towards the W-C interface. At high densities, salt drives the surfactant from the W-C interface to CO 2 and raises. Compared with most hydrocarbon surfactants, this dual tail surfactant is unusually CO 2philic in that it partitions primarily into the CO 2 phase versus the water phase at CO 2 densities above 0.8 g/ml, and produces values below 1 mN/m. With this small , a middle phase microemulsion and a C/W microemulsion were formed at low temperatures and high CO 2 densities, whereas macroemulsions were formed at other conditions.

... The endosulfan K D in soil or sediment tends to increase as soil organic C content increases (Peterson and Batley, 1993; Parkpian et al., 1998). ... Modeling of Endosulfan Runoff The plot of endosulfan concentration in runoff water (C w ) vs. ...

Application of an X-ray fluorescence (XRF) microprobe for the analysis of single grains (80 to 1,000 m in diameter) of Clrich minerals for Br has been evaluated for fluorapatite, chlorapatite, scapolite-group minerals (marialite and meonite) and sodalite. A calibration curve based on the Br contents in four international reference materials has been confirmed by measurements on Brbearing standard solutions and by agreement with the results of Cl-rich minerals from instrumental neutron-activation analyses. Absolute errors associated with individual XRF microprobe analyses (i.e., counting statistics alone) are less than 5%, and the calculated limit of detection in the analysis of single mineral grains is ~1 ppm Br. Matrix and grain-size effects are shown to be negligible. Experiments at 1 atmosphere and 800 to 1000°C yield the following distribution coefficients for Br-Cl exchanges between marialite or sodalite and hydrous NaCl-NaBr melts: K D marialite-melt = 0.97 ± 0.08 and K D sodalite-melt = 0.9 ± 0.1. Therefore, the Cl/Br values in marialite and sodalite closely reflect the halogen proportions of their coexisting melts or fluids. The diffusivity of Br in sodalite follows an Arrhenius relation: D Br = 6.5 ϫ 10-7 exp(-270 ± 10kJ/mol/RT) m 2 /s, over the temperature range from 800 to 1000°C. D Br in marialite is 1.7 ± 0.3 ϫ 10-19 m 2 /s at 800°C. The Cl/Br weight ratios of marialite in the Tieshan Fe skarn deposit, China, cluster around 650 ± 40, supporting an origin involving hydrothermal brines from associated evaporites. Scapolitegroup minerals in the exoskarns of the Nickel Plate Au skarn deposit, British Columbia, have Cl/Br from 560 to 570, higher than those (130 to 180) of their counterparts in the endoskarns and vuggy cavities. This variation is attributable to an increased involvement of magmatic water from distal to proximal zones. Similarly, scapolite-group minerals in the Grenville U-Th-Mo-REE pegmatite-skarn-vein deposits vary widely in Cl/Br, from 80 to 380, indicative of mixed sources of hydrothermal fluids. This study shows the potential of Br analysis of Cl-rich silicate minerals for constraining the sources and evolution of hydrothermal fluids.

In modelling the fate and transport of heavy metals, the sorption processes, through the distribution coecient, are applied to determine the amount of sorbed and dissolved fractions. Usually, these distribution coecients are assumed to depend only on suspended sediment interactions. In estuaries, however, observations indicate that dissolved concentrations increase with salinity. It is hypothesized that salt competes for binding sites, leading to lower distribution coecients. To study the fate and transport of heavy metals in an estuarine environment, a two-dimensional ®nite volume, depth-averaged toxic transport model has been developed. The distribution coecients are approximated as a function of sodium activity or salt concentration. Other model parameters are obtained from a recently developed hydrodynamic model, salt transport and cohesive sediment transport modules. The model has been applied to the Scheldt Estuary and the results for both sorbed and dissolved heavy metal concentrations agree fairly well with measured data, indicating that under estuarine mixing, salt concentration is an important factor aecting the fate and transport of heavy metals.

The distribution coecient of 137 Cs has been determined in 58 soils from 12 sampling points from Biscay by treating 10 g with 25 ml of an aqueous solution with an activity of 1765 Bq in the radionuclide, by shaking during 64 h and measuring the residual activity with a suitable detector. Soils were characterised by sampling depth, particle size analysis and the usual chemical parameters. Soils were thereafter treated to ®x the chemical forms of 137 Cs speciation by successive extractions in order to determine fractions due to exchangeable, associated with carbonates, iron oxide and organic matter fractions, obtaining by dierence the amount taken by the rest of the soil constituents. For this research, 16 soils from four points were selected from the previous samples. The greatest mean percentages of 137 Cs sorption were with the rest (69.93), exchangeable (13.17) and organic matter (12.54%) fractions. This paper includes also the calculation of partial distribution coecients for chemical species as well as relations of distribution coecients both among them and with soil parameters.

Sorption efficacy of phosphatic clay and humus rich soil alone and on combination were tested towards heavy metals present in zinc mine tailing (Zawar Zinc Mine), Udaipur (India). Characterization of the zinc mine tailing sample indicated the presence of Pb, Cu, Zn and Mn in the concentration of 637, 186, 720 and 577 g g −1 , respectively. For sorption efficacy, the zinc mine tailing soil were properly amended with phosphatic clay and humus rich soil separately and in combination and leachability study was performed by batch experiment at different pH range from 3 to 9. The data showed that the percent leachability of heavy metal in non-amended soil was 75-90%. After amendment with phosphatic clay percent leachability of heavy metals became 35-45%. Further, the addition of humus soil to phosphatic clay decreased the percent leachability up to 5-15% at all tested pH. Column leachability experiment was performed to evaluate the rate of leachability. The shape of cumulative curves of Pb, Cu, Zn and Mn showed an increase in its concavity in following order: Pb < Cu < Zn < Mn. The most common selectivity sequence calculated on the basis of distribution coefficient (K d) from the batch experiment was Pb > Cu > Zn > Mn. Further, Langmuir isotherms applied for the sorption studies indicated that phosphatic clay in the presence of humus soil had high affinity for Pb followed by Cu, Zn and Mn, with sorption capacities (b) 139.94, 97.02, 83.32 and 67.58 g g −1 , respectively.

An 11.28 m core collected in Tampa Bay, FL reveals lacustrine sediments during the deglacial warming. Mg/Ca, Sr/Ca and O-18 were measured on two species of brackish water ostracodes. Our interpretation is that variations in Sr/Ca reflect changes in water chemistry and Mg/Ca variations reflect changes in both water temperature and chemistry. Applying Sr distribution coefficients results in virtually identical