Recovery of cesium ions from aqueous solutions with composite sorbents based on tripolite and copper(II) and nickel(II) ferrocyanides

Uptake of cesium ions from aqueous solutions with tripolite modified with nickel(II) and copper(II) ferrocyanides was studied. The composite sorbent based on tripolite and nickel(II) ferrocyanide exhibits the highest sorption-selective (K _d 1.6 × 10⁴ cm³ g^?1 against the background of 0.1 M NaCl) and kinetic properties among the samples studied. It efficiently takes up cesium ions from aqueous solutions, including salt-containing solutions.     

Effect of Structural Variation within Lipophilic Lariat Ether Phosphonic Acid Monoesters on the Selectivity and Efficiency of Competitive Alkali Metal Cation Extraction into Chloroform

Lipophilic lariat ether phosphonic acid monoethyl esters with systematic crown ether ring size variation from 12-crown-4 to 24-crown-8 are utilized for competitive alkali metal cation extractions from aqueous solutions into chloroform. Effective alkali metal cation extraction from weakly acidic, neutral, and basic aqueous solutions is achieved. With 4, 5, and 6 oxygens in the crown ether rings, selectivities for Li(+), Na(+), and K(+), respectively, are observed. An 18-crown-6 phosphonic acid monoester exhibits excellent extraction selectivity for K(+) with K(+)/Li(+) and K(+)/Na(+) > 100. The lipophilic group attachment site, as well as the crown ether ring size, is shown to influence the extraction selectivity for the lariat ether phosphonic monoesters.     

Colloidal Chemical Extraction of Calcium Sulfate and Sorption of Microcomponents of Fresh Water on Calcium Sulfate

Experimental data on colloidal chemical extraction of calcium sulfate formed in supersaturated solutions in fresh water are discussed. When the product of activities of calcium and sulfate ions is artificially exceeded, a nonequilibrium phase with the solubility close to that of CaSO₄ is formed. This phase is extracted into a paraffin melt. Colloidal-chemical extraction of calcium sulfate with paraffin melt and sorption of microcomponents (single-, double-, and triple-charged cations) on calcium sulfate precipitates were studied. The precipitate has high affinity for cesium traces (K _d 10³ mg g^{- 1}) in supersaturated solutions. Some cation species are not sorbed on the precipitate.     

Layered double hydroxide of Zn and Al,intercalated with hexacyanoferrate(II) ions,as a sorbent for removing cesium radionuclides from aqueous solutions

Sorption of cesium radionuclides from aqueous solutions with layered double hydroxide of Zn and Al, intercalated with hexacyanoferrate(II) ions, was studied. The effect of Na⁺, K⁺, and Ca²⁺ on the degree of cesium removal from aqueous solutions was determined, and high selectivity of the sorbent was demonstrated.     

Effect of structural variation within lipophilic N-(X)sulfonyl carbamoyl lariat ethers on the selectivity and efficiency of competitive alkali metal cation extraction into chloroform

Sixteen lipophilic N-(X)sulfonyl carbamoyl lariat ethers with polyether ring sizes of 12-crown-4, 14-crown-4, 15-crown-5, and 18-crown-6 are utilized for competitive alkali metal cation extractions from aqueous solutions into chloroform. Variation of the electron-withdrawing properties of X in the series of methyl, phenyl, 4-nitrophenyl, and trifluoromethyl allows the influence of the acidity of the C(O)NHSO2X group in the side arm upon extraction efficiency and selectivity to be assessed. With X = trifluoromethyl, effective alkali metal cation extractions from acidic, neutral, and basic aqueous solutions are achieved. When the crown ether rings are 14-crown-4, 15-crown-5, and 18-crown-6, selectivities for Li+, Na+, and K+, respectively, are observed. Results are compared with those reported for analogous lariat ether carboxylic acids and phosphonic acid monoethyl esters.     

Electrochemically modulated liquid-liquid extraction of ions

The development of ion extraction methods under electrochemical control via electrochemistry at the interface between two immiscible electrolyte solutions is discussed. A hydrodynamic flow injection system was used for the potentiostatic extraction of non-redox-active species from a flowing aqueous phase into a stationary organogel phase. The ions tetraethylammonium, 4-octylbenzenesulfonate (4-OBSA-), and p-toluenesulfonate (p-TSA-) were studied as model analytes. The extraction study comprised examination of the influence of extraction potentials, aqueous-phase flow rate, and target species concentration. The extraction process can be monitored in situ by means of the ion-transfer current, which has opposing signs for anions and cations. Hydrodynamic voltammograms were obtained from these experiments. The selective extraction of 4-OBSA-, from its mixture with p-TSA-, as well as coextraction of both anions is shown. The results demonstrate the utility of electrochemical modulation for the controlled extraction of ions from an aqueous phase into an organogel electrolyte phase. This offers potential benefits for various analytical processes including sample preparation and cleanup.     

Selective removal of cesium from Acid solutions with immobilized copper ferrocyanide

Copper ferrocyanide can be immobilized on Chelex-20, a technical grade chelating resin, for selective removal of cesium from neutral to acidic solutions. The immobilized copper ferrocyanide is much easier to handle than the copper ferrocyanide powder in extraction and separation of cesium from aqueous solutions. In the presence of a reducing agent such as hydrazine, the immobilized copper ferrocyanide resin is able to remove 98% of the cesium from a simulated acid waste solution in one cycle of batch experiments. The resin shows promising properties for remediation of acidic nuclear wastes and for concentration of (137)Cs from environmental samples for quantitative analysis.     

Effect of the phase volume ratio on the potential of a liquid-membrane ion-selective electrode

Two-phase liquid system IA(w)|IX(o) comprising the interface between the aqueous solution (w) of uni-univalent electrolyte IA and an organic solvent solution (o) of a uni-univalent electrolyte IX with the common cation I(+) is considered as a simple model of a liquid-membrane ion-selective electrode (ISE). Taking into account the electroneutrality and mass balance conditions, the equilibrium Galvani potential difference (pd) between the aqueous and organic phases, phi = phi(w) - phi(o), is calculated numerically as a function of the ratio of the initial electrolyte concentrations, x = / = 10(-)(4)-10(4), for the selected values of the phase volume ratio r = V(o)/V(w) = 10(-)(3), 1, and 10(3), and the standard ion transfer potentials of the present ions ranging from -0.5 to 0.5 V. Numeric results corroborate the symbolic expressions derived for the cases when X(-) and A(-) are extremely lipophilic and hydrophilic ions, respectively, or when the concentration ratio x is extremely large or small. In contrast to the extraction system, where both electrolytes are initially present in the aqueous phase, the effect of the phase volume ratio on the equilibrium pd in the ISE model is rather weak, unless the counterions X(-) and A(-) differ little in their lipophilicity from the target ion I(+). It is shown that both the ISE and extraction model exhibit the Nernstian behavior only in a limited range of the concentration ratio x depending on the value of the standard ion transfer potentials of the counterions. When this ratio is extremely large or small, equilibrium pd approaches the limiting value given by the distribution potential of the electrolyte IA or IX, respectively. Similar conclusions can be drawn for the two-phase liquid system AI(w)|XI(o) with the common anion I(-).     

Selectivity in the coextraction of cation and anion by electrochemically modulated liquid-liquid extraction

Electrochemistry at the interface between two immiscible electrolyte solutions has been presented as a method of electrochemically modulated liquid-liquid extraction, where ions in a mixture can be selectively partitioned as a function of the applied interfacial potential difference. In this study, a mixture comprising 4-octylbenzenesulfonate (4-OBSA-) and tetraethylammonium (TEA+) ions was evaluated. The application of negative potential differences enabled the selective extraction of 4-OBSA- into the organic phase, and more positive potential differences enabled the selective extraction of TEA+. However, intermediate potentials lead to the coextraction of both ions into the organic phase, with apparent selectivity for TEA+ over 4-OBSA-. An increased concentration of either ion in the mixture inhibited the extraction response of the other ion, but the order of the extraction at these intermediate potentials was always TEA+ followed by 4-OBSA-. The reasons for the selectivity for the cation over the anion are discussed.     

Selective removal of cesium ions from aqueous solutions using different inorganic metal hexacyanoferrate-prepared sorbents

Mg-Fe–hexacyanoferrate (MgFeCF) and Ni-Fe–hexacyanoferrate (NiFeCF) were prepared and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy spectra, and thermal analysis. The isotherm study showed that the sorption data fit with the Langmuir and Freundlich isotherms at 25?±?1°C. The sorption capacities of the prepared sorbents for MgFeCF and NiFeCF were found to be 154.32 and 180.83?mg?g^?1, respectively. The adsorption of cesium by MgFeCF and NiFeCF is exothermic and spontaneous processes. Kinetic study indicated that the adsorption of cesium on MgFeCF and NiFeCF fits with the pseudo-second-order kinetic model. Desorption tests indicated that the sorption process is relatively stable. The new sorbents are promising efficient materials for cesium removal from aqueous solutions and sea water. The possibility of reusing the sorbents after stripping the metal ions was studied using 0.5?M HCl, and its efficiency for cesium removal was found to be 98% after five runs.     

MALDI MS analysis of oligonucleotides: desalting by functional magnetite beads using microwave-assisted extraction

The presence of alkali cation adductions of oligonucleotides commonly deteriorates matrix-assisted laser desorption/ionization (MALDI) mass spectra. Thus, desalting is required for oligonucleotide samples prior to MALDI MS analysis in order to prevent the mass spectra from developing poor quality. In this paper, we demonstrate a new approach to extract traces of oligonucleotides from aqueous solutions containing high concentrations of salts using microwave-assisted extraction. The C18-presenting magnetite beads, capable of absorbing microwave irradiation, are used as affinity probes for oligonucleotides with the addition of triethylammonium acetate as the counterions. This new microwave-assisted extraction approach using magnetite beads as the trapping agents and as microwave-absorbers has been demonstrated to be very effective in the selective binding of oligonucleotides from aqueous solutions. The extraction of oligonucleotides from solutions onto the C18-presenting magnetite beads takes only 30 s to enrich oligonucleotides in sufficient quantities for MALDI MS analysis. After using this desalting approach, alkali cation adductions of oligonucleotides are dramatically reduced in the MALDI mass spectra. The presence of saturated NaCl (approximately 6 M) in the oligonucleotide sample is tolerated without degrading the mass spectra. The detection limit for d(A)6 is approximately 2.8 fmol.     

Antagonism in extraction of cesium with 18-crown-6 and phosphine oxides from aqueous perchlorate solution

Liquid-liquid extraction of cesium (spiked with ¹³⁷Cs isotope) with 18-crown-6 in nitrobenzene solvent is diminished in presence of various phosphine oxides, namely, tri-n-octylphosphine oxide (TOPO), tri-n-butylphosphine oxide (TBPO), and triphenylphosphine oxide (TPPO). Formation of an electron donor-acceptor complex between the crown ether and phosphine oxides is assumed, making the crown ether less available for cesium extraction. The formation constants of the complexes were determined by UV-VIS spectrophotometry.     

Effect of humic acids and iron hydroxides deposited on the surface of clay minerals on the 137Cs immobilization

The effect exerted on the relationships of ¹³⁷Cs sorption by humic acids and iron hydroxides deposited on the surface of clay minerals, montmorillonite and kaolinite, differing in the exchange capacity, was studied. The presence of humic acids and Fe(OH)₃ deposited on the mineral surface leads to an increase in the ¹³⁷Cs sorption in a wide pH range (pH 4–9), suggesting the participation of functional groups of humic acids and ferrinol groups of iron(III) hydroxide in binding of the metal ions. The Na⁺, K⁺, and Ca²⁺ ions, on the contrary, with an increase in their concentration in aqueous solution decrease the immobilization of cesium radionuclides and favor their migration in the environment.     

Two-step method for preparation of NaA-X zeolite blend from fly ash for removal of cesium ions

Pure zeolites can be synthesized from silica extracts obtained from fly ash by alkaline leaching. The extraction potential of industrial by-product fly ash was investigated under repeated fusion process conditions. The amount of extracted silica was 131.43 g/kg ash while the amount extracted alumina was limited to 41.72 g/kg ash. The results of zeolite synthesis from the Si-bearing extracts demonstrated that pure zeolites with high cation exchange capacity (4.624 meq/g) can be produced. The sorption potential of synthesized A-X zeolite blend for the removal of cesium ions has been investigated. The influences of pH, contact time and temperature have been reported. Thermodynamic parameters such as changes in Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees) and entropy (DeltaS degrees) were calculated. A comparison of kinetic models applied to the sorption data was evaluated for pseudo first-order, pseudo second-order and homogeneous particle diffusion models. The results showed that both the pseudo second-order and the homogeneous particle diffusion models were found to best correlate the experimental rate data.     

Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2

A magnetic adsorbent, amine-functionalized silica magnetite (NH(2)/SiO(2)/Fe(3)O(4)), has been synthesized to behave as an anionic or cationic adsorbent by adjusting the pH value of the aqueous solution to make amino groups protonic or neutral. NH(2)/SiO(2)/Fe(3)O(4) were used to adsorb copper ions (metal cation) and Reactive Black 5 (RB5, anionic dye) in an aqueous solution in a batch system, and the maximum adsorption were found to occur at pH 5.5 and 3.0, respectively. The adsorption equilibrium data were all fitted the Langmuir isotherm equation reasonably well, with a maximum adsorption capacity of 10.41 mg g(-1) for copper ions and of 217 m g g(-1) for RB5. A pseudo-second-order model also could best describe the adsorption kinetics, and the derived activation energy for copper ions and RB5 were 26.92 kJ mol(-1) and 12.06 kJ mol(-1), respectively. The optimum conditions to desorb cationic and anionic adsorbates from NH(2)/SiO(2)/Fe(3)O(4) were provided by a solution with 0.1M HNO(3) for copper ions and with 0.05 M NaOH for RB5.     

Solvent extraction and stripping of silver ions in room-temperature ionic liquids containing calixarenes

We found that a calix[4]arene-bearing pyridine is soluble in a typical room-temperature ionic liquid (RTIL), 1-alkyl-3-methylimidazolium hexafluorophosphate. Pyridinocalix[4]arene showed a high extraction ability and selectivity for silver ions. The extraction performance of the calix[4]arene was greatly enhanced by dissolution in RTILs compared to in chloroform. In a competitive extraction test using five different metal ions (Ag+, Cu2+, Zn2+, Co2+, Ni2+), only silver ions were transferred by the calix[4]arene from the aqueous feed phase into the RTILs, through a cation-exchange mechanism. The pyridinocalix[4]arene was found to form a stable 1:1 complex with silver ions, both by slope analysis and by Job's method. Since it is easy to strip silver ions from RTILs by controlling the aqueous-phase pH, the extraction performance of calix[4]arene in RTILs was maintained after five repeated uses.     

Enhancement of CsNO3 extraction in 1,2-dichloroethane by tris(2-aminoethyl)amine triamide derivatives via a dual-host strategy

A systematic study of a dual-host system exhibiting pairwise anion/cation separations has been performed for CsNO3 extraction. Tripodal triamides 1-4 and 9 derived from condensation of hexanoic (for 1), octanoic (for 2), decanoic (for 3), lauric (for 4), and p-tert-butylbenzoic (for 9) acid with tris(2-aminoethyl)amine (tren) were used together with tetrabenzo-24-crown-8, a well-known Cs+ cation receptor. By using 5 mM crown ether in the organic phase and 10 mM CsNO3 with 0.1 mM HNO3 in the aqueous phase, tripods 1, 2, and 9 enhance CsNO3 extraction by factors of 2.4, 1.7, and 4.4, respectively (for 50 mM amide concentration), while the corresponding monoamide controls 5-8 derived from n-propylamine (5, 6) or N,N'-dimethylethylenediamine (7, 8) and hexanoic (5, 7) or octanoic (6, 8) acid derivatives gave no significant enhancement under the same conditions. This behavior may be ascribed to nitrate complexation by the triamides, which lowers the overall thermodynamic barrier for the salt transfer to the organic phase. The nitrate binding was confirmed by 1H NMR titration of receptor solutions, using tetrabutylammonium nitrate. Association constants for the formation of the anion-nitrate complexes were found to vary between 33 and 52 M-1 for the more soluble triamides. The synergistic effects for CsNO3 extraction are in reasonable agreement with the values predicted theoretically from the measured association constants. Electrospray ionization mass spectrometry confirmed the predominant formation of 1:1 tripod-nitrate complexes. Monoamide controls gave no evidence of anion complexation.     

Synthesis and properties of 99Tc(I) and 99m Tc(I) hexacarbonyl in aqueous solutions

A procedure was developed for preparing Tc(CO)₆ClO₄ by carbonylation of a solution of technetium(I) tricarbonyltriaqua complex in 2 M HClO₄ in a pressure vessel at 100–170°C and CO pressure of 150 atm. The hexacarbonyltechnetium cation in solution was characterized by IR and ⁹⁹Tc NMR spectroscopy, and also by high-performance liquid chromatography (HPLC). The effect of particular acid and of synthesis conditions on the yield of the hexacarbonyltechnetium cation was examined, and the stability of this cation in aqueous solutions was evaluated. Conditions were found for preparing an aqueous solution containing ^99m Tc(CO) ₆ ⁺ .     

Influence of structural variation in room-temperature ionic liquids on the selectivity and efficiency of competitive alkali metal salt extraction by a crown ether

An improved method for the preparation of 1-alkyl-3-methylimidazolium hexafluorophosphates provides a series of room-temperature ionic liquids (RTILs) in which the 1-alkyl group is varied systematically from butyl to nonyl. For competitive solvent extraction of aqueous solutions of alkali metal chlorides with solutions of dicyclohexano-18-crown-6 (DC18C6) in these RTILs, the extraction efficiency generally diminished as the length of the 1-alkyl group was increased. Under the same conditions, extraction of alkali metal chlorides into solutions of DC18C6 in chloroform, nitrobenzene, and 1-octanol was undetectable. The extraction selectivity order for DC18C6 in the RTILs was K+ > Rb+ > Cs+ > Na+ > Li+. As the alkyl group in the RTIL was elongated, the K+/ Rb+ and K+/Cs+ selectivities exhibited general increases with the larger enhancement for the latter. For DC18C6 in 1-octyl-3-methylimidazolium hexafluorophosphate, the alkali metal cation extraction selectivity and efficiency were unaffected by variation of the aqueous-phase anion from chloride to nitrate to sulfate.     

聚乙二醇-(NH_4)_2SO_4-结晶紫体系中铼的萃取性能研究

研究了聚乙二醇2000(PEG)-(NH4)2SO4-结晶紫双水相体系中,金属离子络合物及萃取剂的光谱行为,探讨了金属离子络合物在PEG相中存在形态及萃取机理。同时实验了在不同酸度、盐用量、萃取剂用量以及在不同表面活性剂的影响下铼的萃取率,通过控制一定条件,可实现了Re(VII)与Mo(VI)的分离。