Sorption of strontium ions from solutions onto calcium and magnesium phosphates

A comparative study of the uptake of Sr ions from aqueous solutions with calcium and magnesium phosphates of various chemical compositions was made. Calcium and magnesium phosphates in the concentration range 10–5000 mg L^?1 absorb up to 280 mg g^?1 Sr, with the ability of magnesium phosphates to take up Sr ions exceeding that of calcium phosphates by an order of magnitude. The degree of decontamination of solutions from ⁹⁰Sr with the magnesium-containing samples exceeds 80%, and the distribution coefficient is (4.7–5.4) × 10³ cm³ g^?1.     

Sorption of strontium ions onto mesoporous manganese oxide of OMS-2 type

Sorption of stable and radioactive strontium ions onto mesoporous manganese oxide of OMS-2 type, prepared by the sol–gel method via reduction of potassium permanganate with polyvinyl alcohol in aqueous medium, was studied. The influence exerted by the pore structure parameters and by the phase and chemical composition of manganese oxide on its sorption properties and selectivity to Sr ions was examined. Manganese oxide samples prepared using a 0.1 wt % KMnO₄ solution exhibit the highest values of the sorption capacity for Sr, about 100–150 mg g^–1, and of the Sr distribution coefficient, K _d = (11.5–19.5) × 10³ cm³ g^–1. Introduction of 0.1 M NaCl into this solution considerably decreases the sorption of stable Sr ions, and for all the samples the sorption capacity is 25–35 mg g^–1. On the other hand, for the most active sorbents the distribution coefficient in the presence of 0.1 M NaCl increases by a factor of approximately 8–10 relative to distilled water and reaches (91–208) × 10³ cm³ g^–1. Introduction of 0.05 M CaCl₂ also decreases the Sr uptake, and the sorption capacity of the most active sorbents for stable Sr ions is 25–35 mg g^–1 at K _d (85Sr) equal to (0.14–0.35) × 10³ cm³ g^–1.     

Sorption of 60Co, 90Sr, 90Y, and 137Cs from aqueous solutions onto Mg-Ln layered double hydroxides (Ln = Ce, Pr, Sm, Gd)

Sorption of ⁶⁰Co, ⁹⁰Sr, ⁹⁰Y, and ¹³⁷Cs from aqueous solutions onto Mg-Ln layered double hydroxides (LDHs) (Ln = Ce, Pr, Sm, Gd) was studied. All the synthesized LDH-Mg-Ln-CO₃ samples (Ln = Ce, Pr, Sm, Gd) sorb ¹³⁷Cs poorly. At a contact time of the solid and liquid phases of 15 min and V/m = 50 mL g^?1, K _d of ¹³⁷Cs is no higher than 1.0 mL g^?1. Despite similar composition of the LDH-Mg-Ln-CO₃ samples (Ln = Ce, Pr, Sm, Gd), they noticeably differ in the ability to sorb ⁹⁰Sr. At a contact time of the solid and liquid phases of 15 min and V/m = 50 mL g^?1, Kd of ⁹⁰Sr varies from 10 to >5 × 10³ mL g^?1. All the synthesized LDHs efficiently sorb ⁹⁰Y and ⁶⁰Co. At a contact time of the solid and liquid phases of 15 min and V/m = 50 mL g^?1, K _d of ⁹⁰Y and ⁶⁰Co from aqueous solutions with LDH-Mg-Ln-CO₃ (Ln = Ce, Pr, Sm, Gd) exceeds 5 × 10³ mL g^?1.     

Sorption properties of rocks on the territory of the former Semipalatinsk test site

The ability of granite and diorite, which are the most abundant rocks on the territory of the Semipalatinsk test site, to take up ¹³⁷Cs and ⁹⁰Sr present in tunnel waters of the Degelen mountain massif was studied in a laboratory. Experiments were performed both with simulated solutions and with real radioactive groundwater. The ¹³⁷Cs distribution coefficients were found for samples of typical granites, albitized granite, quartz porphyry, and diorite from the former Semipalatinsk test site. The ¹³⁷Cs distribution coefficient K _D (cm³ g^?1) was found to be n × 10³–n × 10⁴ for albitized granite, 60–80 for quartz porphyry, and 30–50 for granite. The ability of quartz porphyry and granite to take up ⁹⁰Sr from simulated solutions is characterized by the distribution coefficients K _D = 10–20 cm³ g^?1, and that of albitized granite, by K _D = 110?120 cm³ g^?1. The data obtained are required for predicting the migration of long-lived fission products from the nuclear explosion with underground waters from central zones of underground nuclear explosions in the former Semipalatinsk test site and for calculating the mass transfer in specific geologic media.     

Effect of complexing anions on sorption of U(VI), <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous solutions on layered double hydroxides of Mg,Al, and Nd

Sorption of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on Mg-Al and Mg-Nd layered double hydroxides (LDHs) in various forms was studied. The distribution coefficients K _d of U(VI) and ⁹⁰Sr on LDH-Mg-Al-EDTA are 100–120 ml g⁻¹ in 15 min of contact of the solid and liquid phases at V/m = 50 ml g⁻¹. At the same time, under similar conditions, U(VI) and ⁹⁰Sr are not sorbed from aqueous solutions on LDH-Mg-Al-C₂O₄. The sorption of U(VI) from aqueous solutions containing H₂EDTA²⁻, C₂O₄²⁻, and CO₃²⁻ on LDH-Mg-Nd-CO₃ and LDH-Mg-Al-CO₃ strongly depends on the concentration of the complexing anions in the solution. In particular, for 10⁻³ M aqueous UO₂²⁺ solutions, with an increase in [C₂O₄²⁻] from 10⁻³ to 5 × 10⁻² M, K _d of U(VI) decreases from >5 × 10³ to 70 ml g⁻¹ for LDH-Mg-Al-CO₃ and from 170 to ∼0 ml g⁻¹ for LDH-Mg-Nd-CO₃. In the presence of 10⁻³ to 5 × 10⁻² M CO₃²⁻ in aqueous solution, U(VI) is not noticeably sorbed on LDH-Mg-Nd-CO₃ (K _d does not exceed 16 ml g⁻¹ at V/m = 50 ml g⁻¹), and on LDH-Mg-Al-CO₃ the sorption sharply decreases (K _d decreases from >5 × 10³ to ∼0 ml g⁻¹ at V/m = 50 ml g⁻¹). The presence of complexing anions in the solution does not appreciably affect the ⁹⁰Sr sorption, but noticeably affects the 90Y sorption. With an increase in their concentration, K _d of ⁹⁰Y appreciably decreases. The effect exerted by Sr²⁺ ions on the sorption of microamounts of U(VI) and by UO₂²⁺ ions on the sorption of microamounts of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on LDH-Mg-Nd-CO₃ was also examined.     

Sorption of cesium, strontium, and yttrium radionuclides from the aqueous phase on layered double hydroxides

Sorption of ¹³⁷Cs, ^85,90Sr, and ⁹⁰Y from aqueous solutions on the solid phase of layered double hydroxides (LDHs) and layered double oxides (LDOs) of various compositions was studied. On the solid phase of Mg-Al and Cu-Al LDHs and Mg-Al LDO, the Sr and Cs radionuclides are very weakly sorbed from aqueous solutions containing 10^?5 M of the corresponding element (Cs⁺ or Sr²⁺). Introduction of EDTA ions into Mg-Al LDH increases the distribution coefficients K _d of Sr by a factor of more than 40. After 96-h contact of the solid and liquid phases, K _d of radioactive Sr in sorption from aqueous solution on Mg-Al LDH and Mg-Al LDH-EDTA is 2.4 and 100 ml g^?1, respectively. The Sr and Y radionuclides are efficiently sorbed from aqueous solutions containing 10^?5 M Sr²⁺ and Y³⁺ on the Mg-Nd LDH solid phase. After 5-min contact of the solid and liquid phases, K _d of Sr exceeds 10⁵ ml g^?1. For Y, the distribution coefficients equal to 700–800 ml g^?1 are attained after 30-min contact of the solid and liquid phases. Aging of the Mg-Nd LDH precipitate does not affect its sorption properties toward Sr and Y radionuclides. With an increase in the Sr(NO₃)₂ concentration in the solution from 10^?5 to 10^?1 M, the distribution coefficients K _dz of Sr drastically decrease (virtually to zero) and those of Y change insignificantly.     

Sorption of actinide ions onto mesoporous phosphorus-containing silicas

Equilibrium and kinetic characteristics of template mesoporous silicas containing phosphonic acid residues in sorption of various actinide ions were studied. The sorption equilibrium involving these sorbents is attained within 20 min after introducing the sorbent into the solution. The calculated values of the internal diffusion coefficient \((\bar D)\) and half-exchange time (τ_0.5) in sorption of uranium were ～3.5 × 10^?16 m² s^?1 and ～390 s, respectively. Mesoporous phosphorus-containing silicas efficiently sorb from acid solutions uranyl ions, Th(IV), and Pu(IV). In sorption of uranium from sulfuric acid solutions, the capacity of the sorbents is 125–132 mg g^?1, and in sorption from nitric acid solutions (0.5–3.0 M HNO₃), 276–299 mg g^?1. In sorption of Th(IV) from nitric acid solutions, the capacity of the sorbents is 60–66 mg g^?1. In sorption of microamounts of ²³⁹Pu(IV), the distribution coefficient reaches 4500 cm³ g^?1. Phosphorus-containing silicas in nitric acid solutions do not noticeably sorb ²⁴¹Am, which allows using them for efficient separation of the Pu/Am pair with the separation factor of no less than 2 × 10₃.     

Influence of the concentrations of potassium, sodium, and ammonium ions on the cesium sorption with mixed nickel potassium ferrocyanide sorbent based on hydrated titanium dioxide

The effect of single-charged cations (Na⁺, K⁺, NH ₄ ⁺ ) on the cesium sorption with mixed nickel potassium ferrocyanide sorbent based on hydrated TiO₂ was studied. The K⁺ and Na⁺ ions exert no effect at their concentrations of up to 0.5 M; the Cs⁺ distribution coefficients from KCl and NaCl solutions are (1.1 ± 0.5) × 10⁵ and (8 ± 3) × 10⁴ mL g^?1, respectively. The sorbent is highly specific to Cs⁺ in the presence of ammonium ions. The sorption mechanisms were studied. The concentration ranges in which Cs⁺ and NH ₄ ⁺ are sorbed by independent mechanisms (Cs⁺, by the ferrocyanide phase; NH ₄ ⁺ , by the phase of hydrated TiO₂) and in which the Cs⁺ distribution coefficient decreases owing to competitive filling of the ferrocyanide phase with ammonium ions were determined. At cesium concentrations in solution exceeding 50 mg L^?1, Cs⁺ and NH ₄ ⁺ are absorbed jointly owing to coprecipitation in the mixed ferrocyanide phase in the pore space of the sorbent.     

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 surface modification of hydrated titanium dioxide on its selectivity to strontium

The effect exerted on the selectivity of hydrated TiO₂ to Sr by surface modification of the sorbent involving immobilization of mixed nickel potassium ferrocyanide was studied. The Sr specificity of the resulting sorbent (denoted as T-55) is comparable with that of hydrated TiO₂: logK _d (K _d is Sr distribution coefficient, ml g^?1) is 2.7 ± 0.2 in sorption from tap water with pH 7.8 ± 0.2, 2.7 ± 0.5 in sorption from CaCl₂ solutions with pH 5.6 ± 0.2, and from 2.5 ± 0.8 to 1.7 ± 0.4 in sorption from CaCl₂ solutions with pH 7.0 ± 0.2. The modification makes the resulting T-55 sorbent selective to Sr in the presence of Ca at pH 5–6.     

Sorption of long-lived radionuclides onto main types of rocks of the Novaya Zemlya Archipelago

The ability of black carbonaceous siltstones and silt sandstones, lime sandstones, gray limestones, carbon–silicon carbonate schists with pyrite, and other rocks that most widely occur on the Novaya Zemlya Archipelago to sorb ¹³⁷Cs, ⁹⁰Sr, ^239+240Pu, and ²⁴¹Am was studied. The distribution coefficients K _d (cm³ g^–1) are as follows: for ^239+240Pu, 2.7 × 10³–7.7 × 10³; for 241Am, 2.5 × 10³–1.8 × 10⁴; and for ¹³⁷Cs, 1.1 × 10²–2.0 × 10³. Strontium-85(90) it not noticeably sorbed (within the measurement uncertainty) by any of the rocks studied. ^239+240Pu, ²⁴¹Am, and ¹³⁷Cs are strongly sorbed onto the rocks studied and are not noticeably desorbed from them with distilled water. The data obtained are required for predicting the migration of long-lived radionuclides generated by nuclear explosion with surface waters from test sites on the Novaya Zemlya Archipelago.     

Sorption-barrier properties of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV): 2. Absorption of Am and Pu from groundwater on crushed samples of granitoids and andesite-basaltic metavolcanites and also on their rock-forming minerals

A model study is made of the sorption-barrier properties of crushed samples of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV). In sorption from simulated groundwater (pH 8.3), the volume distribution coefficient K _d of Am was determined to be (0.8–1.6) × 10³ and (3.4–7.0) × 10³ cm³ g^?1, and that of Pu, (0.5–1.7) × 10³ and (1.0–10.0) × 10² cm³ g^?1 for metavolcanites and granitoids, respectively, suggesting good sorption-barrier properties of these rocks. The sorption power of the basic rock-forming minerals of granitoids decreases in the order biotite > feldspar > quartz. The results obtained in this study can be used as input data in predicting the rates of Am and Pu migration with groundwater.     

Removal of <Superscript>90</Superscript>Sr from nitric acid solutions with sorbents based on di-<Emphasis Type="Italic">tert</Emphasis>-butyldicyclohexyl-18-crown-6

A series of impregnated sorbents based on di-tert-butyldicyclohexyl-18-crown-6 (DTBDCH18C6), various diluents (1-octanol, nitrobenzene, telomeric alcohol n3), and supports (Porolas-Т, LPS-500, hydrophobized silica gel) for removing tracer and weighable amounts of Sr ions from nitric acid solutions were prepared. The distribution coefficient of tracer amounts of ⁹⁰Sr on all the synthesized sorbents increases with an increase in the HNO₃ concentration in the range 1–7 M. The most pronounced increase in the sorption occurs with an increase in the HNO₃ concentration to 3 M. The maximal distribution coefficient of ⁹⁰Sr (K _d = 158 cm³ g^–1) is reached for the sorbent based on DTBDCH18C6 and 1-octanol in 7 M HNO₃. Experiments on sorption of weighable amounts of Sr²⁺ ions show that the static capacity of all the prepared sorbents for Sr in nitric acid solutions amounts to 4.3, 9.2, and 8.4 mg g^–1 for the sorbents based on 1-octanol, nitrobenzene, and telomeric alcohol n3, respectively. The synthesized sorbents are suitable for radioanalytical determination of Sr radionuclides in liquid radioactive waste and in radioactively contaminated natural objects.     

Studies on the electrochemical preparation of MgCeCo alloy thin films on Cu substrates in urea–DMSO system

Cyclic voltammetry was used to investigate the electrochemical behaviors of Mg(II), Ce(III) and Co(II) in 3.00 mol L^− 1 urea–DMSO (dimethylsulfoxide). The electrode processes of Mg(II), Ce(III) and Co(II) reducing on Pt electrodes were irreversible steps. The transfer coefficient of Mg(II), Ce(III) and Co(II) in 3.00 mol L^− 1 urea–DMSO system was calculated as 0.07, 0.05 and 0.05 at 298.15 K, respectively. The diffusion coefficient of Mg(II), Ce(III) and Co(II) in 3.00 mol L^− 1 urea–DMSO system was calculated as 2.27 × 10^− 10, 1.77 × 10^− 10 and 3.16 × 10^− 10 m² s^− 1 at 298.15 K, respectively. The MgCeCo alloy thin films with smooth, uniform and metallic luster were obtained on Cu substrates by cyclic electrodeposition in 0.01 mol L^− 1 Mg(ClO₄)₂–0.01 mol·L^− 1 Ce(CH₃SO₃)₃₋0.01 mol L^− 1 CoCl₂–3.00 mol L^− 1 urea–DMSO system. The potential sweep rate was found to be important with respect to the adhesion of the thin films.     

Sorption of Molybdenum onto Titanium Hydroxide

Three types of ionic groups with different pK_i values were revealed for T-5 sorbent by potentiometric titration: for acid groups, pK₁ = 7.5 ± 0.5, pK₂ = 10.2 ± 0.5, and pK₃ = 11.0 ± 0.2; for base groups, pK₄ = 6.5 ± 0.2, pK₅ = 4.5 ± 0.2, and pK₆ = 2.7 ± 0.2. Thus, titanium hydroxide is an amphoteric ion exchanger. Each exchange group of T-5 sorbent, characterized by its definite pK_i value, was assigned to a definite hydroxy group. T-5 and T-52 sorbents exhibit high specificity to Mo in acid and neutral solutions. All the isotherms logC_S–logC_L are described by the Langmuir equation for the polyfunctional sorbent for at least two exchange sites in both nitric and sulfuric acid solutions, irrespective of the Mo speciation. Two groups of values were obtained and confirmed for T-5 and T-52 sorbents depending on the Mo concentration: k_d ≈ 10⁴ mL g^–1 at concentrations lower than 10^–5 M and k_d = 1000–2000 mL g^–1 at a concentration of 10^–5 M. The exchangeable hydroxy groups in T-5 sorbent exhibit high heat resistance, and even the sorbent calcined at 900°C preserves certain reliably measurable capacity for Mo. For T-5, the capacity for Mo only slightly depends on the solution acidity and composition and is about ~1 mmol g^–1.     

Determination of the Parameters of Selective <Superscript>137</Superscript>Cs Sorption onto Natural and Ferrocyanide-Modified Glauconite and Clinoptilolite

The effect exerted by surface modification of natural aluminosilicates, glauconite and clinoptilolite, with ferrocyanides on the parameters of selective ¹³⁷Cs sorption was studied. The modification leads to an increase in the specific sorption and in the radiocesium interception potential in the presence of potassium, RIP(K). RIP(K) of the modified sorbents NPF-Gl and NPF-Cl was 6.1 × 10⁵ and 5.0 × 10⁶ mmol kg^–1, and the specific sorption capacity, 138 ± 14 and 136 ± 12 mg g^–1, respectively. The regular trends in variation of the ¹³⁷Cs distribution coefficients in sorption onto the natural and modified sorbents at K⁺ and Са²⁺ concentrations ranging from 10^–4 to 2.0 M were found. The modified sorbents exhibit high specificity to ¹³⁷Cs in a wide range of Ca and K concentrations in the solutions.     

Influences of hyaluronan on type II collagen fibrillogenesis in vitro

The effect to the kinetics of type II collagen fibrillogenesis with the addition of hyaluronan (HA), (M _w of 1.8 × 10⁶ Da), at various concentrations of HA (0.01, 0.05 and 0.1 wt.%) for a series of fibril formation systems was examined in this study. Evidences deduced from the turbidity–time curves revealed that the inclusion of HA had minor or no impact to the fibrillogenesis of type II collagen (collagen conc. at 0.2 mg/mL). The apparent rate constants, k _lag (lag phase) increased slightly but k _g (growth phase) decreased not very significantly with addition of HA, as compared to the case of pure collagen. This leads us to believe tentatively that, with the addition of HA to collagen solutions, the nucleation process of the fibril formation might have been sped up slightly whereas the growth process slowed up slightly. However, data from TEM observations on the resulting fibrils indicated that the presence of HA did not significantly affect the diameters and the characteristic D-banding periods of the collagen fiber formed. And, from the statistical analyses, we found only insignificant difference (P > 0.05) between the specimens from the various experimental groups. It seems to indicate that the ultimate packing of collagen monomers was probably not interfered or affected significantly by the presence of HA in vitro.     

Thermodynamic and kinetic studies for the adsorption of Hg(II) by nano-TiO2 from aqueous solution

Titanium dioxide nanocrystals were employed, for the first time, for the sorption of Hg(II) ions from aqueous solutions. The effects of varying parameters such as pH, temperature, initial metal concentration, and contact time on the adsorption process were examined. Adsorption equilibrium was established in 420 min and the maximum adsorption of Hg(II) on the TiO₂ was observed to occur at pH 8.0. The adsorption data correlated with Freundlich, Langmuir, Dubinin–Radushkevich (D–R), and Temkin isotherms. The Freundlich isotherm showed the best fit to the equilibrium data. The Pseudo-first order and pseudo-second-order kinetic models were studied to analyze the kinetic data. A second-order kinetic model fit the data with the (k₂ = 2.8126 × 10^?3 g mg^?1min^?1, 303 K). The intraparticle diffusion models were applied to ascertain the rate-controlling step. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were calculated which showed an endothermic adsorption process. The equilibrium parameter (R_L) indicated that TiO₂ nanocrystals are useful for Hg(II) removal from aqueous solutions.     

Transformation of the electronic structure of fullerene C60 caused by complex formation in N-methylpyrrolidone solutions

Evolution of the electronic absorption and photoluminescence spectra of the fullerene C₆₀ solutions with various concentrations in a polar solvent (N-methylpyrrolidone) was studied. Comparison with the electrooptical properties of these solutions shows that a slow (associative) fullerene-solvent interaction mechanism is operative at large (nearly saturating) concentrations (1×10^?3 g/cm³), whereas the solutions of relatively low concentration (less than 5×10^?4 g/cm³) exhibit fast complex formation between fullerene and the solvent molecules. The latter interaction significantly changes the electronic structure of fullerene.     

Applications of L-arginine functionalised green synthesised nickel nanoparticles as gene transfer vector and catalyst

Green synthesised nickel nanoparticles (NiGs) using Ocimum sanctum leaf extract have been stabilised with L-arginine (Arg–NiGs) and used as gene transfer vector for bacterial transformation and as catalyst for hydrolytic dehydrogenation. Effective binding of L-arginine with NiGs was confirmed by characterisation of Arg–NiGs. L-arginine coating on NiGs prevented the agglomeration of NiGs and reduced the size of the nanoparticles. Synthesised Arg–NiGs was conjugated with green fluorescent protein (GFP) inserted pUC 18 (pDNA–Arg–NiGs) and employed for transforming non-competent Escherichia coli DH5 α. Transformation efficiency of pDNA–Arg–NiGs was found to be higher (3.8 × 10⁶ µg^–1 DNA) than the CaCl₂-mediated method (2.9 × 10⁵ µg^–1 DNA). Fluorescence micrograph of transformants showed enhanced uptake and transformation of pDNA–Arg–NiGs by bacterial cells. Electrophoretic analysis of expressed GFP confirmed that pDNA could retain its functional activity even after binding with Arg–NiGs. This biocompatible, efficient and economical method could be exploited for transforming non-competent bacterial cells. Arg–NiGs catalysed hydrolytic dehydrogenation of ammonia borane (AB) generated 198 mL of hydrogen in 8 min with 128 mg AB and 10 mL of catalyst at 35 °C. The hydrogen generation rate of Arg–NiGs catalysed AB dehydrogenation was determined to be 24.8 mol H₂ min^–1 with activation energy (E_a) of 34.05 kJ mol^–1 and turnover frequency (TOF) of 12.30 mol H₂ (mol Ni) ^–1 min^–1. Arg–NiGs retained 89% of its initial catalytic activity even after 10 recycles, indicating its high durability in catalytic reactions. Kinetic studies of AB dehydrogenation by Arg–NiGs show the first-order kinetics with respect to catalyst concentration and zero-order kinetics with respect to AB concentration. This efficient and durable catalyst could be applied in hydrolytic dehydrogenation of AB for effective hydrogen storage.