首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 45 毫秒
1.
《Applied Geochemistry》2006,21(4):675-683
In acidic soils and aquatic environments, polymeric hydroxyaluminum (HyAl) cations with various OH/Al ratios are ubiquitous. Hydroxyaluminum-montmorillonite (HyAl-Mt) complexes are widely distributed in acidic to slightly acidic soils and aquatic environments. The fixation of HyAl cations on Mt can significantly modify the mineralogical and electrochemical properties of the host clay, thereby substantially influencing adsorption/desorption and transport of many nutrients and pollutants. In the present study, HyAl-Mt complexes were synthesized through adsorption of polymeric HyAl cations with OH/Al ratio of 1.6 on Na-saturated Mt (Na-Mt). Interaction of F− with HyAl-Mt was investigated in acidic conditions and the environmental implications for F−-contaminated soils were also addressed. Results indicated that the effects of pH on F− sorption by HyAl-Mt were slight in the pH range of 5.0–9.0, whereas sorption increased rapidly with decreasing pH when pH was below 4.5. At initial pH >4.0, ligand exchange was the main mechanism for F− sorption. At initial pH 3.02 and high initial F− concentrations, several synergic mechanisms, such as coprecipitation, scavenging and surface adsorption were involved in F− removal from solution, which resulted in an abrupt and discontinuous increase in sorption capacity of HyAl-Mt for F− with increasing initial F− concentration, and a slight dependency of F− sorption on HyAl-Mt dosage. Compared with Na-Mt, sorption capacities of HyAl-Mt for F− were significantly enhanced by interlayering and coating with polymeric HyAl cations. HyAl-Mt would be important natural scavengers for F−. The presence of HyAl-Mt in acidic soils could greatly retard F− transport and bioavailability in soil environments. Interaction of F− with HyAl-Mt may mitigate acidification of F−-contaminated acidic soils. Application of synthetic HyAl-Mt may be one alternative for remediation of acidic F−-contaminated soils.  相似文献   

2.
《Applied Geochemistry》1999,14(5):569-579
Potential human intrusion into the Waste Isolation Pilot Plant (WIPP) might release actinides into the Culebra Dolomite where sorption reactions will affect of radiotoxicity from the repository. Using a limited residence time reactor the authors have measured Ca, Mg, Nd adsorption/exchange as a function of ionic strength, PCO2, and pH at 25°C. By the same approach, but using as input radioactive tracers, adsorption/exchange of Am, Pu, U, and Np on dolomite were measured as a function of ionic strength, PCO2, and pH at 25°C. Metal adsorption is typically favored at high pH. Calcium and Mg adsorb in near-stoichiometric proportions except at high pH. Adsorption of Ca and Mg is diminished at high ionic strengths (e.g., 0.5M NaCl) pointing to association of Na+ with the dolomite surface, and the possibility that Ca and Mg sorb as hydrated, outer-sphere complexes. Sulfate amplifies sorption of Ca and Mg, and possibly Nd as well. Exchange of Nd for surface Ca is favored at high pH, and when Ca levels are low. Exchange for Ca appears to control attachment of actinides to dolomite as well, and high levels of Ca2+ in solution will decrease Kds. At the same time, to the extent that high PCO2s increase Ca2+ levels, Kds will decrease with CO2 levels as well, but only if sorbing actinide-carbonate complexes are not observed to form (Am-carbonate complexes appear to sorb; Pu-complexes might sorb as well. U-carbonate complexation leads to desorption). This indirect CO2 effect is observed primarily at, and above, neutral pH. High NaCl levels do not appear to affect to actinide Kds.  相似文献   

3.
Significant amounts of sulfuric acid (H2SO4) rich saline water can be produced by the oxidation of sulfide minerals contained in inland acid sulfate soils (IASS). In the absence of carbonate minerals, the dissolution of phyllosilicate minerals is one of very few processes that can provide long-term acid neutralisation. It is therefore important to understand the acid dissolution behavior of naturally occurring clay minerals from IASS under saline–acidic solutions. The objective of this study was to investigate the dissolution of a natural clay-rich sample under saline–acidic conditions (pH 1–4; ionic strengths = 0.01 and 0.25 M; 25 °C) and over a range of temperatures (25–45 °C; pH 1 and pH 4). The clay-rich sample referred to as Bottle Bend clay (BB clay) used was from an IASS (Bottle Bend lagoon) in south-western New South Wales (Australia) and contained smectite (40%), illite (27%), kaolinite (26%) and quartz (6%). Acid dissolution of the BB clay was initially rapid, as indicated by the fast release of cations (Si, Al, K, Fe, Mg). Relatively higher Al (pH 4) and K (pH 2–4) release was obtained from BB clay dissolution in higher ionic strength solutions compared to the lower ionic strength solutions. The steady state dissolution rate (as determined from Si, Al and Fe release rates; RSi, RAl, RFe) increased with decreasing solution pH and increasing temperature. For example, the highest log RSi value was obtained at pH 1 and 45 °C (−9.07 mol g−1 s−1), while the lowest log RSi value was obtained at pH 4 and 25 °C (−11.20 mol g−1 s−1). A comparison of these results with pure mineral dissolution rates from the literature suggests that the BB clay dissolved at a much faster rate compared to the pure mineral samples. Apparent activation energies calculated for the clay sample varied over the range 76.6 kJ mol−1 (pH 1) to 37.7 kJ mol−1 (pH 4) which compare very well with the activation energy values for acidic dissolution of monomineralic samples e.g. montmorillonite from previous studies. The acid neutralisation capacity (ANC) of the clay sample was calculated from the release of all structural cations except Si (i.e. Al, Fe, K, Mg). According to these calculations an ANC of 1.11 kg H2SO4/tonne clay/day was provided by clay dissolution at pH 1 (I = 0.25 M, 25 °C) compared to an ANC of 0.21 kg H2SO4/tonne clay/day at pH 4 (I = 0.25 M, 25 °C). The highest ANC of 6.91 kg H2SO4/tonne clay/day was provided by clay dissolution at pH 1 and at 45 °C (I = 0.25 M), which is more than three times higher than the ANC provided under the similar solution conditions at 25 °C. In wetlands with little solid phase buffering available apart from clay minerals, it is imperative to consider the potential ANC provided by the dissolution of abundantly occurring phyllosilicate minerals in devising rehabilitation schemes.  相似文献   

4.
Elevated concentrations of arsenic in the sediment and pore water in the Sundarban wetlands pose an environmental risk. Adsorption and desorption are hypothesized to be the major processes controlling arsenic retention in surface sediment under oxic/suboxic condition. This study aims to investigate sorption kinetics of As(III & V) and its feedback to arsenic mobilization in the mangrove sediment. It ranges from sand to silty clay loam and shows the adsorption of As(III & V) following the Langmuir relation. Estimates of the maximum adsorption capacity are 59.11 ± 13.26 μg g−1 for As(III) and 58.45 ± 8.75 μg g−1 at 30°C for As(V) in the pH range 4 to 8 and salinity 15–30 psu. Extent of adsorption decreases with increasing pH from 4 to 8 and desorption is the rate-limiting step in the reaction of arsenic with sediment. Arsenic in the sediment could be from a Himalayan supply and co-deposited organic matter drives its release from the sediment. Arsenic concentration in the sediment is well below its maximum absorption capacity, suggesting the release of sorbed arsenic in pore water by the microbial oxidation of organic matter in the sediment with less feedback of adsorption.  相似文献   

5.
《Applied Geochemistry》2004,19(6):835-841
Experiments on dissolution kinetics of galena were performed in 1 mol l−1 NaCl solutions at pH 0.43–2.45 and 25–75 °C. When the dissolution reaction is far from equilibrium, a linear relation exits between the dissolution rate, r, and the H+ ion activity, [H+]. The rate law for galena dissolution is given by the following equation: r=k[H+]. With respect to H+, the dissolution reaction is in the first order. The apparent rate constant, k, has values of 2.34×10−7 mol m−2 s−1 at 25 °C, 1.38×10−6 mol m−2 s−1 at 50 °C, and 7.08×10−6 mol m−2 s−1 at 75 °C. The activation energy of dissolution reaction is 43.54 kJ mol−1. The mechanism of dissolution is suggested to be surface chemical reaction, and the rate determining step is the dissociation of the Pb–S bond of the surface complex, which releases Pb2+ into the solution.  相似文献   

6.
《Applied Geochemistry》2001,16(9-10):1067-1082
Thermodynamic data for all fate-determining processes are needed in order to predict the fate and transport of metals in natural systems. The surface complexation properties of a synthetic MnO2, δ-MnO2, have accordingly been investigated using glass electrode potentiometry. Experimental data were interpreted according to the surface complexation model in conjunction with the diffuse double layer model of the solid/solution interface. Adsorption constants were determined using the non-linear optimisation program FITEQL. Surface complexation parameters determined in this way were validated against results obtained from the literature. Best fits of alkalimetric titration data were obtained with a 2-site, 3 surface-species model of the δ-MnO2 surface. Site concentrations of 2.23×10−3 mol g−1 and 7.66×10−4 mol g−1 were obtained. Corresponding logarithms of formation constants for the postulated surface species are −1.27 (≡XO−), −5.99 (≡YO−) and 3.52 (≡YOH2+) at I=0.1 M. The surface speciation of δ-MnO2 is dominated by ≡XO− over the pH range investigated. Metal adsorption was modelled with surface species of the type ≡XOM+, ≡XOMOH, ≡YOM+, ≡YOMOH (M=Cu, Ni, Zn, Cd and Pb) and ≡XOM2OH2+ (M=Pb). For Cu, Ni and Zn, titration data could be modelled with ≡XOM+, ≡XOMOH, ≡YOM+ and ≡YOMOH, whereas for Cd, ≡XOM+ and ≡YOM+ were sufficient. Lead data were best modelled by assuming the dinuclear species ≡XOM2OH2+ to be the only surface species to form. Adsorption constants determined for Ni, Cu and Zn follow the Irving-Williams sequence. The model suggests an adsorption order of (Pb, Cu) > (Ni, Zn) > Cd. The discrepancy between model predictions and published adsorption results is similar to the variability observed in experimental results from different laboratories.  相似文献   

7.
《Applied Geochemistry》2002,17(4):399-408
The sorption of U(VI) onto the surface of olivine has been experimentally investigated at 25 °C under an air atmosphere as a function of pH, solid surface to volume ratio and total U concentration. Sorption has been observed to decrease as the extent of carbonate complexation of U(VI) in solution increases, which is attributed to the competition between aqueous and solid ligands for the coordination of U. The experimental results have been interpreted by means of two different approaches: (1)a semi-empirical model, exemplified by the application of a Langmuir isotherm and (2) a non-electrostatic thermodynamic surface complexation model which includes the formation of the surface species: >SO–UO2+ and >SO–UO2(OH). The following stability constants for these species have been determined from the thermodynamic analysis: K(>SO–UO2+)=289±71 and K(>SO–UO2(OH))=(3.4±0.4)×10−6. The comparison of the sorption of U onto olivine with granites of different origin indicate that the use of this mineral as additive to the backfill of deep high level nuclear waste repositories could retard the migration of U from the repository to the geosphere.  相似文献   

8.
  相似文献   

9.
Adsorption of Cr(VI) on γ-alumina was investigated as a function of ionic strength (0.001, 0.01 and 0.1 M NaNO3), pH (4-10), Cr(VI) concentration (10−4 or 10−5 M with 5 g/L solid) and pCO2 (0, atmospheric, 2.5%). Cr(VI) sorption is significant at low pH and decreases with increasing pH, with 50% of the Cr(VI) adsorbed between pH ∼6.5 and 8. Adsorption varies little with ionic strength or pCO2 under most of the studied conditions. However, at low pH under high ionic strength and especially at high ionic strength and high pCO2, Cr(VI) sorption on γ-alumina is suppressed. The adsorption edge data were used to parameterize constant capacitance (CCM), diffuse double layer (DLM) and triple layer (TLM) surface complexation models. None of the models entirely captures the full range of observed adsorption dependence on ionic strength and sorbate/sorbent ratio. The best fits to the full dataset are produced by the CCM, mostly because it has ionic-strength dependent stability constants. The more sophisticated TLM, which requires the most fitting parameters, does not produce better fits than the simpler CCM or DLM approaches for the conditions tested in this study.  相似文献   

10.
Lead is one of the most dangerous contaminants which has been released to the environment during many years by anthropogenic activities. Adsorption of Pb2+ on vermicompost was studied at 11°C, 30 °C and 50 °C by using Langmuir and Freundlich models, that adequately described the adsorption process, with maximum adsorption capacities were 116.3; 113.6 and 123.5 μg/g for each temperature. The differences in FTIR (Fourier Transform Infrared Spectrometer) spectra of vermicompost at pH 3,8 and pH 7.0 in the region from 1800 to 1300 cm-1 were interpreted on the basis of carboxyl acid ionization that reduce band intensity around 1725 cm-1 producing signals at 1550 cm-1(νa) and 1390 cm-1 (νa) of carboxylate groups. Similar changes were detected at pH 3.8 when ionic lead was present suggesting that heavy metal complexation occurs throughout a cationic exchange reaction. Vermicompost was applied to a soil where white bean plants were planted. After irrigation with lead nitrate solutions the uptake of lead was reduced to 81 % in leaves and stem, while the reduction in the roots was around 50 %. The highest accumulation of lead was found in the roots and the translocations seems to be limited by the presence off vermicompost in the soil.  相似文献   

11.
《Geochimica et cosmochimica acta》1999,63(19-20):3261-3275
Studies on the dissolution kinetics of kaolinite were performed using batch reactors at 25°C and in the pH range from 1 to 13. A rapid initial dissolution step was first observed, followed by a linear kinetic stage reached after approximately 600 hr of reaction during which the kaolinite dissolves congruently at pH < 4 and pH > 11. The apparent incongruency between pH 5 and 10 was due to the precipitation of an Al–hydroxide phase. The true dissolution rates were computed from the amount of Si released into solution. The rate dependence on pH can be described by: r = 10−12.19aH+0.55 + 10−14.36 + 10−10.71aOH−0.75Between pH 5 and 10, the rate is approximately constant, although a smooth minimum was observed at pH close to 9. mAn attempt was made to obtain a general rate law based on the coordination theory, which was first applied to the mineral dissolution studies by Stumm and co-workers. The kinetic data were combined with the results obtained for the surface speciation by Huertas et al. (1998). It is possible to express the linear dissolution rate as a simple power function of the concentration of the surface sites active in various pH ranges: r = 10−8.25 [>Al2OH2+] + 10−10.82 [>AlOH2+]0.5 + 10−9.1 [>Al2OH + >AlOH + >SiOH] + 103.78 [>Al2O− + >AlO−]3This equation assumes that the dissolution mechanism is mainly controlled by the two Al surface sites (external and internal structural hydroxyls, and aluminol at the crystal edges) under both acidic and alkaline conditions. The model reflects well the important contribution of the crystal basal planes to the dissolution of kaolinite.  相似文献   

12.
《Applied Geochemistry》2001,16(13):1499-1512
The oxidative dissolution rate of metacinnabar by dissolved O2 was measured at pH ∼5 in batch and column reactors. In the batch reactors, the dissolution rate varied from 3.15 (±0.40) to 5.87 (±0.39) × 10−2 μmol/m2/day (I=0.01 M, 23°C) and increased with stirring speed, a characteristic normally associated with a transport-controlled reaction. However, theoretical calculations, a measured activation energy of 77 (±8) kJ/mol (I=0.01 M), and the mineral dissolution literature indicate reaction rates this slow are unlikely to be transport controlled. This phenomenon was attributed to the tendency of the hydrophobic source powder to aggregate and minimize the effective outer surface area. However, in a column experiment, the steady-state dissolution rate ranged from 1.34 (±0.11) to 2.27 (±0.11) x 10−2 μmol/m2/day (I=0.01 M, 23°C) and was also influenced by flow rate, suggesting hydrodynamic conditions may influence weathering rates observed in the field. The rate of Hg release to solution, under a range of hydrogeochemical conditions that more closely approximated those in the subsurface, was 1 to 3 orders of magnitude lower than the dissolution rate due to the adsorption of released Hg(II) to the metacinnabar surface. The measured dissolution rates under all conditions were slow compared to the dissolution rates of minerals typically considered stable in the environment, and the adsorption of Hg(II) to the metacinnabar surface further lowered the Hg release rate.  相似文献   

13.
In a high-level radioactive waste (HLW) repository, pH has an impact on the solubility, migration, and adsorption of radionuclides. Thus, understanding the effects of pH on the diffusion of radionuclides is essential for long-term disposal of HLW. In this work, the diffusion behaviors of Re(VII) and Se(IV) in compacted Gaomiaozi (GMZ) bentonite at different pH have been investigated by a through-diffusion method. The effective diffusion coefficient, i.e., De values of Re(VII) and Se(IV) were in the range of (1.0–2.4) × 10−11 m2/s at pH 3.0–10.0 and (0.38–2.3) × 10−11 m2/s at pH 3.0–9.0. In the case of Re(VII), the De values remained almost unchanged probably because ReO4− was the dominant species in the pH range of 3.0–10.0. In the case of Se(IV), whose predominant species were HSeO3− at pH < 9.0 and SeO32− at pH ≥ 9.0, the De values decreased by a factor of 3–6 at pH 9.0, i.e., De (pH < 9.0)/De (pH 9.0) ≈ 3–6, implying that the species with a higher valence state had a stronger anion exclusion effect. The decrease in De values can be explained by the diffusion species of Se(IV). Additionally, the rock capacity factor α decreased with the increase of pH. HSeO3− was absorbed on GMZ bentonite with distribution coefficient Kd values in the range of (1.0–2.5) × 10−4 m3/kg at pH ≤ 8.0, whereas SeO32− was negligibly sorbed at pH > 8.0.  相似文献   

14.
Adsorption onto Fe-containing minerals is a well-known remediation method for As-contaminated water and soil. In this study, the use of acid mine drainage sludge (AMDS) to adsorb As was investigated. AMDS is composed of amorphous particles and so has a large surface area (251.2 m2 g−1). Here, adsorption of both arsenite and arsenate was found to be almost 100%, under various initial AMDS dosages, with the arsenate adsorption rate being faster. The optimum pH for As adsorption onto AMDS was pH 7.0 and the maximum adsorption capacities for arsenite and arsenate were 58.5 mg g−1 and 19.7 mg g−1 AMDS, respectively. In addition, experiments revealed that AMDS dosages decreased As release from contaminated soil. Therefore, the AMDS used in this study was confirmed to be a suitable candidate for immobilizing both arsenite and arsenate in contaminated soils.  相似文献   

15.
《Geochimica et cosmochimica acta》1999,63(19-20):3183-3191
Hydrothermal atomic force microscopy (HAFM) provides in situ access to the surfaces of dissolving crystals at temperatures above the ambient boiling point of water. Here, we applied HAFM to the (001) surfaces of labradorite and anorthite at temperatures up to 125°C. In HCl solutions (pH 2) we observed the formation of a rough and soft surface layer on both minerals. By applying high loading forces to the scanning tip, the soft layer can be removed and the underlying interface (between the fresh solid and the altered layer) can be observed. In this way, in situ information about the thickness of the altered layer on plagioclase and the morphology of the underlying interface can be obtained. On labradorite, the thickness of this layer does not exceed about 30 nm within the first 5 hr of exposure to acidic solution at 125°C, but on anorthite thicknesses of up to about 300 nm were observed. The uncovered interface on anorthite shows a nonuniform morphology and either appears rough in AFM images or shows a step-like pattern.On anorthite, etch pits spread underneath the altered layer. This suggests that material must be released and transported through the layer without obvious changes in morphology of the layer’s surface. Based on the rate of spreading of etch pits, the dissolution rate was calculated to be about 2 × 10−6 mol m−2 s−1 at 125°C. This value agrees reasonably well with literature data and supports the suggestion that dissolution mainly takes place underneath the altered layer and not on its surface.  相似文献   

16.
《Applied Geochemistry》2001,16(7-8):793-802
The adsorption of As(V) onto α-Al2O3 was investigated at 25, 50 and 70°C using batch adsorption experiments. Results indicate that As is strongly adsorbed at low pH and gets progressively released to the fluid with increasing pH above 7. At any pH, increasing temperature favors aqueous species of As over surface species. Surface complexation constants were determined at the experimental temperatures by fitting the adsorption data. Adsorption reactions were then converted to semi-isocolumbic reactions, i.e. reactions with balanced like-charged aqueous species. Intrinsic adsorption constants of semi-isocolumbic reactions change linearly when plotted against inverse temperature, suggesting that the heat capacity of these reactions remains constant over the temperature range considered. This permitted thermodynamic parameters of intrinsic surface complexation constants to be determined. Changes in surface complexation constants result in a change in the surface speciation with increasing temperature. This change is similar to the one observed for aqueous species, i.e. increasing temperature favors less negatively charged species below a pH of 9 and more negatively charged species above a pH of 10. Comparison with the stability of As surface complexes with Fe suggests that surface complexes with Al are more stable.  相似文献   

17.
《Applied Geochemistry》2003,18(4):527-538
Thermodynamic parameters for proton and metal adsorption onto a gram-negative bacterium from the genus Enterobacteriaceae have been determined and compared with parameters for other strains of bacteria. Potentiometric titrations were used to determine the different types of sites present on bacterial cell walls. Stability constants for adsorption of Pb, Cu and Zn to specific sites were determined from batch adsorption experiments at varying pH with constant metal concentration. Titrations revealed 3 distinct acidic surface sites on the bacterial surface, with pK values of 4.3±0.2, 6.9±0.5 and 8.9±0.5, corresponding to carboxyl, phosphate and hydroxyl/amine groups, with surface densities of 5.0±0.7×10−4, 2.2±0.6×10−4 and 5.5±2.2×10−4 mol/g of dry bacteria. Only carboxyl and phosphate sites are involved in metal uptake, yielding the following intrinsic stability constants: Log Kcarboxyl: Zn=3.3±0.1, Pb=3.9±0.8, and Cu=4.4±0.2, Log Kphosphoryl: Zn=5.1±0.1 and Pb=5.0±0.9. The deprotonation constants are similar to those of other strains of bacteria, while site densities are also within an order of magnitude of other strains. The similarities in surface chemistry and metal stability constants suggest that bacteria may be represented by a simple generic thermodynamic model for the purposes of modelling metal transport in natural environments. Comparison with oxide-coated sand shows that bacteria can attenuate some metals to much lower pH values.  相似文献   

18.
Arsenate and antimonate are water-soluble toxic mining waste species which often occur together and can be sequestered with varying success by a hydrous ferric oxide known as ferrihydrite. The competitive adsorption of arsenate and antimonate to thin films of 6-line ferrihydrite has been investigated using primarily adsorption/desorption kinetics monitored by in situ attenuated total reflectance infrared (ATR-IR) spectroscopy on flowed solutions containing 10−3 and 10−5 mol L−1 of both species at pH 3, 5, and 7. ICP-MS analysis of arsenate and antimonate adsorbed to 6-line ferrihydrite from 10−3 mol L−1 mixtures in batch adsorption experiments at pH 3 and 7 was carried out to calibrate the relative surface concentrations giving rise to the IR spectral absorptions. The kinetic data from 10−3 and 10−5 mol L−1 mixtures showed that at pH 3 antimonate achieved a greater surface concentration than arsenate after 60 min adsorption on 6-line ferrihydrite. However, at pH 7, the adsorbed arsenate surface concentration remained relatively high while that of adsorbed antimonate was much reduced compared with pH 3 conditions. Both species desorbed slowly into pH 3 solution while at pH 7 most adsorbed arsenate showed little desorption and adsorbed antimonate concentration was too low to register its desorption behaviour. The nature of arsenate which is almost irreversibly adsorbed to 6-line ferrihydrite remains to be clarified.  相似文献   

19.
《Geochimica et cosmochimica acta》1999,63(19-20):3217-3227
A natural illite (illite du Puy) was purified and converted to the homo-ionic Na form. The conditioned Na–illite was characterised in terms of its mineralogy, chemical inventory, and surface properties. The structural formula was determined from EDS analyses (SEM/TEM) and bulk chemistry. A cation exchange capacity of 127 mEq/kg was determined by the Na isotope dilution method at neutral pH.The sorption of Cs was measured as a function of NaClO4 background electrolyte concentration (1.0, 0.1 and 0.01 M), Cs concentration and pH in the range ≈3 to ≈10. Before obtaining these measurements the kinetics of Cs uptake were determined at initial concentrations of 2 × 10−8 M and 7 × 10−5 M, representing the extremes of the range investigated, and was found to be concentration dependent. The supernatant solutions after centrifugation were analysed for major cations in all of the sorption tests.A two-site cation exchange model was developed to describe the sorption of Cs over the whole range of experimental conditions. The two-site types were termed frayed edge sites, FES (high affinity/low capacity) and type II sites (low affinity/high capacity). At low NaClO4 concentrations, Cs sorption decreased at pH values less than neutral. This was interpreted in terms of competitive effects from H, and K released by the partial dissolution of illite, which cannot be avoided at low and high pH values. Selectivity coefficient values for Cs–Na, Cs–K, K–Na, and H–Na exchange equilibria on the FES sites, and Cs–Na exchange on the type II sites are given for illite together with the corresponding site capacities.  相似文献   

20.
《Geochimica et cosmochimica acta》1999,63(19-20):3133-3143
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号