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1.
The sorption of Eu(III) on calcareous soil as a function of pH, humic acid (HA), temperature and foreign ions was investigated
under ambient conditions. Eu(III) sorption on soil was strongly pH dependent in the observed pH range. The effect of ionic
strength was significant at pH < 7, and not obvious at pH > 8. The type of salt cation used had no visible influence on Eu(III)
uptake on soil, however at low pH values, the influence of anions was following the order: Cl − ≈ NO 3
− > ClO 4
−. In the presence of HA, the sorption edge obviously shifted about two pH units to the lower pH, whilst in range of pH 6–7,
the sorption of Eu(III) decreased with increasing pH because a considerable amount of Eu(III) was present as humate complexes
in aqueous phase, then increased again at pH > 11. The results indicated that the sorption of Eu(III) on soil mainly formed
outer-sphere complexes and/or ion exchange below pH ~7; whereas inner-sphere complexes and precipitation of Eu(OH) 3(s) may play main role above pH ~8. 相似文献
2.
The adsorption behavior of Eu(III) from aqueous solution to mesoporous molecular sieves (Al-MCM-41) is investigated as a function
of contact time, solid content, ionic strength, pH, foreign ions and temperature by using batch technique. The experimental
results show that Eu(III) adsorption is strongly dependent on pH values, but independent of ionic strength and foreign cations
under our experimental conditions. The kinetic process is described by a pseudo-second-order rate model very well. The adsorption
isotherms are simulated by Langmuir model very well. The thermodynamic parameters (∆ G°, ∆ S°, ∆ H°) are calculated from the temperature dependent adsorption isotherms at 293, 313 and 333 K, respectively, and the results
suggest that the adsorption of Eu(III) on Al-MCM-41 is a spontaneous and endothermic process. Desorption studies indicate
that the adsorbed Eu(III) is very difficult to be desorbed from the solid surface. Al-MCM-41 is a suitable material for the
preconcentration and solidification of Eu(III) from large volumes of aqueous solutions. 相似文献
3.
Batch sorption experiments were performed to remove Eu(III) ions from aqueous solutions by using attapulgite under ambient
conditions. Different experimental conditions, such as contact time, solid content, foreign ions, pH, ionic strength, fulvic
acid and temperature, have been investigated to study their effect on the sorption property. The results indicated that the
sorption of Eu(III) onto attapulgite was strongly dependent on pH, ionic strength and temperature. The sorption increased
from about 8.9 to 90% at pH ranging from 2 to 6 in 0.01 mol/L NaNO 3 solution. The Eu(III) kinetic sorption on attapulgite was fitted by the pseudo-second-order model better than by the pseudo-first-order
model. The sorption of Eu(III) onto attapulgite increased with increasing temperature and decreasing ionic strength. The Langmuir
and Freundlich models were used to simulate the sorption isotherms, and the results indicated that the Freundlich model simulated
the data better than the Langmuir model. The thermodynamic parameters (∆ G
o, ∆ S
o, ∆ H
o) were determined from the temperature dependent isotherms at 298.15, 318.15 and 338.15 K, and the results indicated that
the sorption reaction was an endothermic and spontaneous process. The results suggest that the attapulgite is a suitable material
as an adsorbent for preconcentration and immobilization of Eu(III) from aqueous solutions. 相似文献
4.
The extraction of Am, Eu, Ce(III), Zr(IV), and Sr from aqueous nitric acid— nitrate media by dibutyl N,N-diethylcarbamylphosphonate
and dibutyl N,N-diethylcar-bamylmethylenephosphonate dissolved in carbon tetrachloride was studied. The trivalent actinide
and lanthanide elements may be separated in certain aqueous phase acidity regions from Fe(III), Zr(IV), and Sr, whereas the
separation of actinide elements from the lanthanide elements is poor. The extractant to metal ratio in the extracted complexes
of Am, Eu, and Ce(III) is 3. The interferences in the extraction due to acidic impurities in the extracting agent are discussed. 相似文献
5.
Herein, the sorption properties of Eu(III) on Na-attapulgite were performed by using batch sorption experiments under different
experimental conditions, such as contact time, pH, ionic strength, humic acid and temperatures. The results indicated that
the sorption of Eu(III) on Na-attapulgite was strongly dependent on pH and temperature. At low pH values, the sorption of
Eu(III) was influenced by ionic strength, whereas the sorption was not affected by ionic strength at high pH values. The sorption
of Eu(III) was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, and by inner-sphere
surface complexation or surface precipitation at high pH values. The sorption of Eu(III) onto Na-attapulgite increased with
increasing temperature. The Langmuir and Freundlich models were applied to simulate the sorption isotherms, and the results
indicated that the Langmuir model simulated the sorption isotherms better than the Freundlich model. The thermodynamic parameters
(∆ G
o, ∆ S
o, ∆ H
o) were calculated from the temperature dependent sorption isotherms at 293, 313 and 333 K, respectively, and the results indicated
that the uptake of Eu(III) on Na-attapulgite was an endothermic and spontaneous process. The results of high Eu(III) sorption
capacity on Na-attapulgite suggest that the attapulgite is a suitable material for the preconcentration and immobilization
of Eu(III) ions from large volumes of aqueous solutions. 相似文献
6.
The competitive sorption of Cu(II) and Eu(III) ions from aqueous solutions by olive-cake carbon, has been investigated by
potentiometry at pH 6, I=0.1 M NaClO 4, 25°C and under normal atmospheric conditions. Evaluation of the experimental data supports the formation of inner-sphere
surface complexes and results in the calculation of the formation constant of the surface complexes ((=S–O) 2Cu), which is found to amount log β
Cu=5.3±0.3. Addition of competing Eu(III) ions in the aqueous system leads to replacement of the Cu(II) by the competitor metal
ion. Evaluation of the potentiometric data obtained from competition experiments indicates an ion-exchange mechanism. The
formation constant of the Eu(III) species sorbed on olive cake carbon is found to be log β
Eu=5.1±0.5. Comparison of the complex formation constants of the olive-cake carbon with the corresponding complex formation
constants for of olive cake and humic acid with the two metal ions, indicates that the same type of active sites is responsible
for the metal ion complexation on the surface of the different types natural organic matter (e.g. olive-cake carbon, olive-cake
and humic acid). 相似文献
7.
In the present study, Mg–Al layered double hydroxide intercalated with nitrate anions (LDH-NO 3) was synthesized, modified with the anionic surfactant, sodium lauryl sulfate, and applied for the removal of 152+154Eu from aqueous solutions. Modification of the as-synthesized Mg–Al layered double hydroxide was carried out at surfactant
concentration of 0.01 M (the organo-LDH produced denoted LDH-NaLS). The as-synthesized and surfactant-intercalated LDHs were
characterized by FT-IR and energy-dispersive X-ray spectroscopy techniques. The effect of some variables such as solution
pH, contact time and sorbate concentration on removal of 152+154Eu was investigated. The kinetic data obtained were well fitted by the pseudo-second-order kinetic model rather than the pseudo-first-order
model. Intraparticle diffusion model showed that sorption of 152+154Eu proceed by intraparticle diffusion together with boundary layer diffusion. Experimental isotherm data were well described
by Langmuir model. Organo-LDH was found to have higher capacity (156.45 mg g −1) for europium than the as-synthesized LDH-NO 3 (119.56 mg g −1). Comparing LDHs capacities obtained for Eu(III) in the present work with other sorbents reported in literature indicated
that LDHs have the highest capacities. Application of the developed process for removal of 152+154Eu(III) from radioactive process wastewaters was also studied and the obtained results revealed that these LDHs are promising
materials for treatment of radioactive wastewaters. 相似文献
8.
A new chelating polymeric sorbent has been developed using polystyrene resin grafted with phosphonic acid. After characterization
by FTIR and elementary analysis, the new resin has been investigated in liquid–solid extraction of europium(III). The results
indicated that phosphonic resin could adsorb Eu(III) ion effectively from aqueous solution. The adsorption was strongly dependent
on pH of the medium with enhanced adsorption as the pH value of 6.5. The influence of other analytical parameters including
contact time, amount of resin, metal ion concentration, and ionic strength were investigated. The maximum uptake capacity
of Eu(III) ions was 122.6 mg/g grafted resin at ambient temperature, at an initial pH value of 6.50. The overall adsorption
process was best described by pseudo first-order kinetic. When Freundlich and Langmuir isotherms were tested, the latter had
a better fit with the experimental data. Furthermore, Eu(III) could be eluted by using 1.0 mol/L H 2SO 4 solution and the grafted resin could be regenerated and reused. 相似文献
9.
Resorcinol–formaldehyde aerogels (five samples, three of them with addition of nitrogen containing precursors—3-hydroxypyridine,
3-aminophenol and melamine) have been prepared by sol–gel polycondensation, subcritical drying and pyrolysis. The pyrolysis
of prepared organic aerogels has been studied by non-isothermal TG at constant heating rate. The process of pyrolysis has
been found to consist of three steps with the total mass loss 40.2–61.7% (room temperature—1,000 °C). The resulted carbon
aerogels have been tested as sorbents of Ni(II), Pb(II) and Cu(II) ions from aqueous solutions. Various relations have been
found among the results obtained from the pyrolysis experiments and properties affecting adsorption. Besides the expected
correlation between the mass loss gained from TG (isothermal step at 500 °C was applied) and from heating in the laboratory
oven, the relationship between the mass loss during pyrolysis and sorption capacities for all three metal ions has been found.
Other relations among pyrolysis behaviour, surface area and content of nitrogen have been also examined. Batch adsorption
experiments show (with an exception of one sample) that N-doped samples have higher adsorption capacity for metal ions. In
addition, changing of nitrogen functionalities during the pyrolysis has been considered and pyridinic-N (N-6) functionality
has been contemplated as a suitable structure for the adsorption process. 相似文献
10.
A very simple and quick analytical method, based on direct aqueous injection, for determination of halogenated solvents in
refinery water and wastewater, is described. There is a need to determine halogenated solvents in refinery water streams,
because they may originate from several processes. There is also a need to develop methods enabling VOX to be determined in
samples containing oil fractions. The method described enables simultaneous determination of 26 compounds with low detection
limits (sub-μg L −1) and excellent precision, especially for highly halogenated solvents. The matrix effects of four types of sample were evaluated—the
method seemed to be relatively insensitive to variations in matrix composition. Deuterated 1,2-dichloroethane was used as
internal standard and surrogate compound in quantitative analysis; application of isotopically labelled compounds is rarely
reported when non-mass spectrometric detectors are used for analysis. Analysis of real samples showed that the most frequently
detected compounds were dichloromethane and 1,2-dichloroethane. 相似文献
11.
A simple, inexpensive method based on solid-phase extraction (SPE) on sawdust from Cedrus deodera has been developed for speciation of Cr(III) and Cr(VI) in environmental water samples. Because different exchange capacities
were observed for the two forms of chromium at different pH—Cr(III) was selectively retained at pH 3 to 4 whereas Cr(VI) was
retained at pH 1—complete separation of the two forms of chromium is possible. Retained species were eluted with 2.5 mL 0.1 mol L −1 HCl and 0.1 mol L −1 NaOH. Detection limits of 0.05 and 0.04 μg mL −1 were achieved for Cr(III) and Cr(VI), respectively, with enrichment factors of 100 and 80. Recovery was quantitative using
250 mL sample volume for Cr(III) and 200 mL for Cr(VI). Different kinetic and thermodynamic properties that affect sorption
of the chromium species on the sawdust were also determined. Metal ion concentration was measured as the Cr(VI)–diphenylcarbazide
complex by UV–visible spectroscopy. The method was successfully applied for speciation of chromium in environmental and industrial
water samples. 相似文献
12.
The competitive sorption of Cu(II), Eu(III) and U(VI) ions in aqueous solutions by TiO 2, has been investigated by potentiometry at I = 0.1 M NaClO 4, 25 °C and under atmospheric conditions. For Cu(II) ions the investigation was performed directly by means of a Cu 2+ ion selective electrode, whereas for the Eu(III) and U(VI) ions indirectly based on competition reactions between the Cu(II) ion and the Eu(III) and U(VI) ions. Numerical analysis of the experimental data supports the formation of inner-sphere surface complexes and allows the evaluation of the formation constant of the (TiO) 2Cu, which is found to amount to log β* = 4.3 ± 0.4. Addition of competing Eu(III) and U(VI) ions in the aqueous system leads to replacement of the Cu(II) by the competitor metal ion. Evaluation of the potentiometric data obtained from competition experiments indicates on an ion exchange mechanism. The formation constant of the Eu(III) and U(VI) species adsorbed on TiO 2 is found to be log β* = 4.4 ± 0.7 and 4.8 ± 0.8, respectively. The relative affinity of the TiO 2 surface for the metal ions under investigation is U(VI) > Eu(III) > Cu(II). 相似文献
13.
The question whether fatigue is induced during mechanical pulping was addressed experimentally. The grinding process was interrupted
to image partly ground spruce samples. The grinding was performed at five different feed velocities using two different grindstones.
This approach allowed creating an in situ snapshot of the developing grinding zone in the wood samples. The depth profiles
of the stiffness modulus and nm-scale pores, close to and within, the grinding zone were quantified by ultrasonic pitch-catch
measurements and thermoporosimetry. To perform these profiling measurements, wood material was iteratively removed layer-by-layer
with a microtome from the sample surface after taking the snapshot. The grinding-induced changes in cell morphology inside
the sample were imaged using microcomputed tomography, whereas the changes on the surface of the samples were imaged with
optical microscopy and SEM. A layer that penetrated 0.5–1.5 mm into the sample exhibiting up to 80% decreased stiffness modulus—compared
to the unaltered sample parts—was detected when the Wave-type grindstone was employed. The corresponding layer thickness was
0.3 mm with the conventional grindstone. The results match previously measured temperature profiles, and confirm the Atack-May
hypothesis that grinding induces a fatigue layer. Confirming this old, widely used hypothesis is significant for the field
of energy efficiency research related to mechanical pulping and may provide new opportunities for grinding research. 相似文献
14.
Two approaches—substrate nanostructuring and incorporation of sulfide—were studied with the aim to increase electrochemical
capacitance of cobalt (hydro)oxide. A fiber structure of cobalt was deposited electrochemically with the fibers in the order
of tens of nanometers in thickness and hundreds of nanometers in length. Cobalt hydroxide film was formed on the nanostructured
substrate by anodic polarization in an alkaline solution. The hydroxide formation and its electrochemical capacitance have
been studied by cyclic voltammetry in conjunction with the electrochemical quartz crystal microbalance (EQCM). An irreversible
behavior was typical of the first anodic polarization cycle; it turned gradually to a reversible one during subsequent cycling.
EQCM measurements indicated exponential electrode mass growth during the first cycle, with subsequent transition to a quasipassive
state. The redox transitions Co(II) → Co(III) → Co(IV), which determine pseudocapacitance, did not cause remarkable electrode
mass change. The electrochemical capacitance of the nanofiber sample was found up to five times higher when compared to that
formed on conventional cobalt (abraded surface). Specifics of “per 1 g” evaluation of capacitance performance is discussed.
Measurements showed that about 10% of the entire hydroxide structure took part in the capacitive process. The capacitance
value determined per 1 g of active Co(OH) 2 was in agreement with the limiting value predicted by the Faraday’s law (2,421 F g −1) sulfide-enhanced system with 18% CoS exhibited up to three times higher capacitance when compared to that of the sulfide-free
counterpart. The system shows promise for practical applications due to its low cost and technical simplicity. 相似文献
15.
Naringinase from Penicillium species—containing α- l-rhamnosidase and β- d-glucosidase activity—immobilized on silicate carriers can be used as a mild and effective means to cleave naturally occurring
glycosides into their aglycones and sugar components. The procedure was tested with flavonoid-, anthraquinone-, and steroidglycosides.
Since the solubility of such compounds is limited in aqueous solutions, a simple batch procedure has been developed to convert
solid substrates suspended in only small amounts of buffer to the desired products with high yields. 相似文献
16.
A new technique to analyze aqueous samples for nanograms per liter levels of volatile and semivolatile compounds using microextraction and thermal desorption into a gas chromatograph/ion trap mass spectrometer (GC/MS) is described. This method is inherently sensitive (50 mL of aqueous sample is extracted prior to each desorption), uses no solvents, and detects volatiles and semivolatiles in the same analysis. Aqueous standards and environmental samples are pumped through a length of porous-layer open-tubular capillary column, which is then thermally desorbed onto a 30 m × 0.25 mm i.d. analytical column interfaced to an ion trap mass spectrometer for subsequent separation and detection. Sharp chromatographic peaks and reproducible retention times (RT) were observed. Replicate injections of surrogates ( n = 6) averaged 32.6% R.S.D. Analysis of domestic tap water detected 55 analytes, some at the low-nanograms per liter level, and detected 3 halogenated ethenes, not previously reported in drinking water. Analysis of an aqueous sample from a municipal ground water source detected the presence of numerous semivolatile compounds at trace-levels. 相似文献
17.
The separation of americium(III) from europium(III) was achieved utilizing a bis-2,6-(5,6,7,8-tetrahydro-5,9,9-trimethyl-5,8-methano-1,2,4-benzotriazin-3-yl) pyridine (CA-BTP) chromatographic resin. The extraction chromatographic materials were prepared using various concentrations of CA-BTP. This new, hydrolytically stable extractant was impregnated on an inert polymeric support at 40% loading. The uptake of Am(III) and Eu(III) by this material from 0.1 to 4.0 M aqueous HNO3 solutions was measured. The resulting dry weight distribution ratios, D
w
, indicated a strong preference for Am(III) with little affinity for Eu(III). These results are similar to recently reported solvent extraction studies indicating a maximum uptake of Am(III) in the 0.5–1.0 M HNO3 range. The resin preparation, performance, and characterization of the Am/Eu separation are reported herein. 相似文献
18.
Dispersive liquid—liquid microextraction coupled with high-performance liquid chromatography—diode-array detection was applied
for the extraction and determination of 11 priority pollutant phenols in wastewater samples. The analytes were extracted from
a 5-mL sample solution using a mixture of carbon disulfide as the extraction solvent and acetone as the dispersive solvent.
After extraction, solvent exchange was carried out by evaporating the solvent and then reconstituting the residue in a mixture
of methanol–water (30:70). The influences of different experimental dispersive liquid—liquid microextraction parameters such
as extraction solvent type, dispersive solvent type, extraction and dispersive solvent volume, salt addition, and pH were
studied. Under optimal conditions, namely pH 2, 165-μL extraction solvent volume, 2.50-mL dispersive solvent volume, and no
salt addition, enrichment factors and limits of detection ranged over 30–373 and 0.01–1.3 μg/L, respectively. The relative
standard deviation for spiked wastewater samples at 10 μg/L of each phenol ranged between 4.3 and 19.3% ( n = 5). The relative recovery for wastewater samples at a spiked level of 10 μg/L varied from 65.5 to 108.3%. 相似文献
19.
Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on their origins. The information on the difference in the structure of these complexes is scarce. To participate in the filling of this lack, a study of the spectral and temporal evolution of the Eu(III) luminescence implied in humic substance (HS) complexes is presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) and humic acid (SRHA), and Leonardite HA (LHA) from the International Humic Substances Society (USA), humic acid from Gorleben (GohyHA), and from the Kleiner Kranichsee bog (KFA, KHA) from Germany, and purified commercial Aldrich HA (PAHA), were made to contact with Eu(III). Eu(III)-HS time-resolved luminescence properties were compared with aqueous Eu 3+ at pH 5. Using an excitation wavelength of 394 nm, the typical bi-exponential luminescence decay for Eu(III)-HS complexes is common to all the samples. The components τ1 and τ2 are in the same order of magnitude for all the samples, i.e., 40 ≤ τ1 (μs) ≤ 60, and 145 ≤ τ2 (μs) ≤ 190, but significantly different. It is shown that different spectra are obtained from the different groups of samples. Terrestrial extract on the one hand, i.e. LHA/GohyHA, plus PAHA, and purely aquatic extracts on the other hand, i.e., SRFA/SRHA/KFA/KHA, induce inner coherent luminescent properties of Eu(III) within each group. The 5D 0 → 7F 2 transition exhibits the most striking differences. A slight blue shift is observed compared to aqueous Eu 3+ ( λmax = 615.4 nm), and the humic samples share almost the same λmax ≈ 614.5 nm. The main differences between the samples reside in a shoulder around λ ≈ 612.5 nm, modelled by a mixed Gaussian–Lorentzian band around λ ≈ 612 nm. SRFA shows the most intense shoulder with an intensity ratio of I612.5/ I614.7 = 1.1, KFA/KHA/SRHA share almost the same ratio I612.5/ I614.7 = 1.2–1.3, whilst the LHA/GohyHA/PAHA group has a I612.5/ I614.5 = 1.5–1.6. This shows that for the two groups of complexes, despite comparable complexing properties, slightly different symmetries are awaited. 相似文献
20.
Silicate mesoporous mesophases analogous to SBA-3 or MCM-41 with the hexagonal (honeycomb) structure can be synthesized in
a moderately acidic region (pH ∼2.5—5). The synthesis was carried out using aqueous solutions of sodium silicate and a surfactant
of the alkyltrimethylammonium bromide type as the starting precursors.
For Part 4, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 29–34, January, 2008. 相似文献
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