Sorption Of Strontium Research Articles

Differences and implications of strontium distribution coefficient on various granite compositional materials.

The distribution coefficient (Kd) of radionuclides is a crucial parameter in assessing the safety of high-level radioactive waste (HLW) geological repository. It is determined in the laboratory through batch and column experiments. However, differences in obtained Kd values from distinct experiments have not been thoroughly assessed and compared. This study evaluated strontium (Sr) sorption on different granite materials using static batch and dynamic experiments (column and core-flooding experiments). The results from batch sorption experiments showed higher Sr sorption on granite under acidic and strongly alkaline conditions, low solid-liquid ratios, and low ionic strength. In column experiments, a two-site sorption model was used to simulate Sr transport in crushed granite and mixed pure minerals. The sorption of Sr on crushed granite exhibited a higher affinity than that of mixed pure minerals. The dual-porosity transport model was employed to investigate Sr transport behavior in fractured granite in the core-flooding experiment. Kd obtained from batch sorption experiments are four to twenty times higher than those from column experiments, and two to three orders of magnitude higher than that from a core-flooding experiment. The results of this study provide valuable insights into safety assessment for the HLW geological repository.

Effect of grain size variation on strontium sorption to heterogeneous aquifer sediments

Strontium-90 (90Sr) is a major contaminant at nuclear legacy sites. The mobility of 90Sr is primarily governed by sorption reactions with sediments controlled by high surface area phases such as clay and iron oxides. Sr2+ adsorption was investigated in heterogeneous unconsolidated aquifer sediments, analogous to those underlying the UK Sellafield nuclear site, with grainsizes ranging from gravels to clays. Batch sorption tests showed that a linear Kd adsorption model was applicable to all grainsize fractions up to equilibrium [Sr] of 0.28 mmol L−1. Sr2+ sorption values (Kd; Langmuir qmax) correlated well with bulk sediment properties such as cation exchange capacity and surface area. Electron microscopy showed that heterogeneous sediments contained porous sandstone clasts with clay minerals (i.e. chlorite) providing an additional adsorption capacity. Therefore, gravel corrections that assumed that the > 2 mm fractions are inert were not appropriate and underestimated Kd(bulk) adsorption coefficients. However, Kd (<2 mm) values measured from sieved sediment fractions, were effectively adjusted to within error of Kd (bulk) using a surface area dependant gravel correction based on particle size distribution data. Amphoteric pH dependent Sr2+ sorption behaviour observed in batch experiments was consistent with cation exchange modelling between pH 2–7 derived from the measured cation exchange capacities. Above pH 7 model fits were improved by invoking a coupled cation exchange/surface complexation which allowed for addition sorption to iron oxide phases. The overall trends in Sr2+ sorption (at pH 6.5–7) produced by increasing solution ionic strength was also reproduced in cation exchange models. Overall, the results showed that Sr2+ sorption to heterogeneous sediment units could be estimated from Kd (<2 mm) data using appropriate gravel corrections, and effectively modelled using coupled cation exchange and surface complexation processes.

Effective sorption of strontium and cobalt ions from aqueous solutions using strong acid polystyrene gel cation exchange resin

ABSTRACT This article examined reducing the hazardous effects of Sr(II) and Co(II) using a sodium-based purolite C100 cation exchange adsorbent. The sorption behaviour of Sr(II) and Co(II), including the impact of time, pH, initial concentrations, and temperature. The results reveal that purolite C100 has a fast equilibrium time and follows pseudo-2nd-order kinetics. The saturation capacity has high values of 190.5 and 182.1 mg g−1 for Sr(II) and Co(II), respectively. The Langmuir isotherm model is more applicable than other isotherm models. Negative Gibbs energy values demonstrated the excellent feasibility and spontaneity of the sorption process. Positive enthalpy readings indicate that this process was endothermic. Positive entropy values demonstrated that the disorder between the solid and liquid phases was enhanced during adsorption. Desorption of Sr(II) and Co(II) from the loaded purolite C100 was done by KCl (99.2%) and CaCl2 (99.3%), respectively. The recycling results indicated that the purolite C100 should be reused for repeated sorption-desorption regeneration cycles up to 14 cycles, with a low reduction in the uptake percentage. The excellent recycling results reveal the applicability of the purolite C100 to be used as an effective cation exchange adsorbent for the sorption of Sr(II) and Co(II) from aqueous media.

The Effect of High-Energy Ball Milling of Montmorillonite for Adsorptive Removal of Cesium, Strontium, and Uranium Ions from Aqueous Solution

Clay minerals are widely used to treat groundwater and surface water containing radionuclides. In our study, the method of mechanochemical activation for increasing the sorption capacity of the natural clay mineral montmorillonite was used. By adjusting the grinding time, the increasing sorption parameters of mechanochemically activated montmorillonite were determined. X-ray diffraction method, scanning electron microscopy, and the determination of the specific surface by low-temperature adsorption–desorption of nitrogen to characterize the natural and mechanochemical-activated montmorillonites were used. It was established that the maximal sorption of uranium, strontium, and cesium is found for montmorillonite after mechanochemical treatment for 2 h. It is shown that the filling of the surface of montmorillonite with ions of different natures occurs in various ways during different times of mechanochemical treatment. The appropriateness of the Langmuir and Freundlich models for the sorption parameters of uranium, strontium, and cesium ions on montmorillonite after its mechanochemical activation was established. The effect of natural organic substances—humic acids—on the efficiency of water purification from uranium on mechanoactivated montmorillonite was studied. The obtained sorbents can be effectively used for the removal of trace amounts of radionuclides of different chemical natures (uranium, cesium, and strontium) from polluted surface and ground waters.

Microbial Impacts on Colloid-Radionuclide Interactions

Microorganisms can play an important role on the behaviour of colloids in natural and engineered environments, which in turn can control the mobility of associated metals and radionuclides. This is especially true in the nuclear fuel cycle, where radionuclides (including uranium) can interact with a broad range of inorganic colloids. This is relevant to the legacy spent nuclear fuel ponds at Sellafield, which house a diverse inventory of waste from the early Magnox reactors. These reactors used uranium metal as a fuel encased in a magnesium non-oxide cladding. Corrosion of the cladding results in the release of radionuclides, primarily uranium, and the formation of brucite (Mg(OH)2) phases which are present both in the corroded Magnox sludge at the base of the pond and suspended in the water column as colloids (Gregson et al. 2011). These brucite colloids have the potential to mobilise insoluble phases providing an important pathway for radionuclide migration. The spent nuclear fuel ponds are maintained at high pH to minimise corrosion of the cladding, however significant corrosion has still occurred. Despite the seemingly inhospitable conditions in spent nuclear fuel ponds, numerous studies have found microorganisms capable of surviving in spent nuclear fuel ponds (Dekker et al. 2014, Foster et al. 2020, Ruiz-Lopez et al. 2020). Previous work has demonstrated increased abiotic sorption of strontium to brucite in the presence of organic matter derived from Pseudanabaena catenata (Ashworth et al. 2018), which dominates algal blooms in the ponds. In this study we focus on uranium interactions with colloidal brucite in the presence of microbes adapted to high pH environments under conditions relevant to the spent nuclear fuel ponds at Sellafield.

Controlled reprocessing of leucoxene concentrate for environmental friendly production of titanosilicate – An effective sorbent for strontium and cesium ions

An environmentally friendly synthesis procedure of titanosilicate with sitinakite structure from quartz-leucoxene concentrates processing products for effective sorption of strontium and cesium ions has been designed. The proposed method minimizes the environmental impact by controlling the acidity of waste waters and reuse of fluorammonium component in the technological process of enrichment (fluorination) of mineral raw materials. The sitinakite synthesis procedure excludes the stage of additional mechanical activation of quartz-leucoxene concentrate using complex and energy-consuming equipment. The precipitate composition and formation of SiO2-TiOn complex aggregates is controlled through step-by-step hydrolysis of dissolved forms of compounds. The new approach reduces sitinakite synthesis temperature and allows regulating composition, crystallinity and sorption properties of titanosilicate. The sorption capacity of the obtained sitinakite by Sr2+ and Cs+ cations is 120 and 170 mg/g, respectively, and does not decrease when its crystallinity changes.

Investigating the influence of bentonite colloids on strontium sorption in granite under various hydrogeochemical conditions

The disposal of high-level radioactive waste in deep geological repositories is a critical environmental issue. The presence of bentonite colloids generated in the engineering barrier can significantly impact the transport of radionuclides, but their effect on radionuclide sorption in granite remains poorly understood. This study aimed to investigate the sorption characteristics of strontium (Sr) on granite as well as on the coexistence system of granite and colloids under various hydrogeochemical conditions, through batch experiments. Fourier transform infrared spectroscopy was employed to analyze the sorption forms of Sr on granite before and after sorption. Several hydrogeochemical factors were examined, including contact time, pH, ionic strength, coexisting ions, and bentonite and humic acid colloid concentration. Among these factors, the concentration of bentonite colloids exhibited a significant effect on Sr sorption. Within a specific range of colloid concentration, the sorption of Sr on the solid system increased linearly with the bentonite colloid concentration. pH and ionic strength were also found to play crucial roles in the sorption process. At low pH, Sr sorption primarily occurred through the outer sphere's surface complexation and Na+/H+ ion exchange. However, at high pH, inner sphere surface complexation dominated the process. As the ionic strength increased, electrostatic repulsion gradually increased, resulting in fewer binding sites for particle aggregation and Sr sorption on bentonite colloids. The results also indicate that with increasing pH, the predominant forms of Sr in the solution transitioned from SrHCO3+ and SrCl+ to SrCO3 and SrCl+. This was mainly due to the ion exchange of Ca2+/Mg2+ in plagioclase and biotite, forming SrCO3 precipitation. These findings provide valuable insights into the transport behavior of radionuclides in the subsurface environment of the repository and highlight the importance of considering bentonite colloids and other hydrogeochemical factors when assessing the environmental impact of high-level radioactive waste disposal.

Fast and effective sorption of radioactive Sr(II) onto mesoporous silicate

Abstract A mesoporous silicate material (MS) was effectively synthesized and applied as a solid sorbent for removal of radioactive Sr(II) ions from aqueous solution. MS was characterized using different tools including N2 adsorption-desorption analysis, FT-IR, XRD and SEM. The synthesized material has crystalline, porous nature and exhibited a large surface area of about 905.18 m2 g−1. The uptake of Sr(II) ions onto MS was investigated under different batch experimental conditions involving pH, equilibrium time, sample weight and initial concentration of Sr(II) ions. About 98 % of Sr(II) radionuclides were uptaken at pH 12 in the first minute. Different isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich and Temkin) were applied to analyze the obtained experimental sorption equilibrium data. The Langmuir isotherm model was aligned well with the sorption data. The maximum sorption capacity (Q max) of MS towards strontium ions attained the value 0.991 mmol/g. The parameters (ΔG°, ΔH° and ΔS°) were calculated from thermodynamic study and their values showed that sorption process of Sr(II) ions on MS is strong, take place spontaneously, and considered as endothermic process. The synthesized MS had the ability to efficiently remove Sr(II) radionuclides even in the presence of Na+ and Ca2+ as competing cations in aqueous solution. Among the studied desorbing agents, CaCl2 was the best one for desorbing Sr(II) radionuclides loaded onto MS. The synthesized MS was reused for sorption of strontium up to four cycles with acceptable efficiency.

Strontium transport modeling in high-concentrated nitrate solution in DEEP liquid radioactive waste repository

This article focuses on modeling 90Sr migration in strong nitrate solutions in aquifers used for radioactive waste disposal. This type of radioactive waste disposal is typical only for the Russian Federation and is a unique object of study. The calculations are based on the laboratory study of strontium sorption in nitrate solutions on sandy, loamy and clayey rocks under biotic (with natural microbial communities obtained from Seversky repository) and abiotic conditions. To obtain a strontium sorption model, first, an ion exchange model in PHREEQC software is fitted to the experimental data both manually and automatically (using MOUSE software). Since real nitrate-ion concentrations at radioactive waste injection sites can reach values of hundreds of grams per liter, strontium Kd values are predicted for high ionic strength (for which no experimental study of strontium sorption efficiency has been carried out) with PHREEQC-model. The strontium transport models accounting for sorption and the nitrate reduction processes have been developed using two numerical software packages: the GeRa 3D hydrogeological simulation code and the PHREEQC reactive transport code. Reactive transport modeling under different conditions shows a high sensitivity to dispersion. A significant effect of sorption of nitrate ion on Sr sorption is shown and a relatively small contribution of microbial processes to strontium transport is noted for liquid radioactive waste injection sites.

137Cs, 85Sr and 60Co sorption from model solutions of low activity liquid radioactive waste by modified oil shale

The results of the study of cesium, strontium, cobalt radionuclides sorption from model solutions simulating liquid radioactive waste on promising sorbents based on thermally modified oil shale are presented. The dependency of texture parameters obtained from the results of nitrogen adsorption-desorption on the treatment method of oil shale and their relationship to sorption parameters such as distribution coefficient and removal efficiency was discussed. Understanding how pore characteristics affect the sorption activity of such complex systems as sorbents is important for the creation of radionuclide sorption materials with improved characteristics. The efficiency of sorption of cesium, strontium and cobalt radionuclides was rather high for sorbent samples: the distribution coefficient was about 103–104 ml/g with a removal efficiency of more than 66 %. The most effective sorbent was obtained from oil shale with a heating rate of 5 deg/min without subsequent steam treatment, which is recommended to be used for low-active radioactive waste treatment.

Effect of Competing Ions on Multisorption (Cs+, Sr2+) by Composite Sorbents Based on Natural and Synthetic Zeolites

In the course of the research, the effect of competing ions (Na+) on multisorption (Cs+, Sr2+) by composite sorbents based on natural and synthetic zeolites under static conditions was studied. It was found that the maximum concentration of competing ions (0.4 g of NaCl per 100 ml of solution) leads to a decrease in cesium sorption by 20%, and strontium sorption decreases by 10%. At the same time, high rates of sorption of cesium and strontium are preserved. Thus, for a composite sorbent (clinoptilolite -30%: zeolite NaX -70%), the sorption of cesium was 67.9%, and the sorption of strontium was 87.6%. The analytical technique was developed on the basis of the PIXE (Proton Induced X-ray Emission) method and made it possible to qualitatively and quantitatively determine the content of isotopes. The work was performed at the analytical nuclear-physical complex "Sokil". The energy range of the electrostatic accelerator is 200-2000 keV. The complex made it possible to carry out all the main methods of analysis using ion beams. The targets were placed in the exit, at the Chamber for PIXE. To carry out measurements, a vacuum with a pressure of 10-4 Pa was created in the chamber. To excite the atoms of cesium, strontium, a proton beam with an energy of Ер≈1400 keV was used. The characteristic X-ray radiation of the L-series of cesium atoms and K-series of strontium atoms was recorded by two detectors: XR-100CR Si-PIN X-Ray and Ge(HP). The sorption coefficient (Sorption, %) was used as a quantitative characteristic of the interaction of sorbents with cesium, strontium.

A Study of Sr Sorption Behavior in Claystone from a Candidate High-Level Radioactive Waste Geological Disposal Site under the Action of FeOOH Colloids.

Colloids have a significant influence on the migration of nuclides in claystone, which is an important geological barrier. The sorption of strontium on claystone in the presence of FeOOH colloids was investigated in samples from the Suhongtu site, a candidate high-level radioactive waste disposal site in China. The effects of colloid amount, solid content, and pH were investigated by batch tests, and the sorption reaction mechanism was analyzed by kinetic modeling and microscopic characterization techniques. The results indicate that the sorption of Sr by claystone increased with the solids content, and the claystone had a stronger Sr sorption capacity under alkaline conditions. The Sr sorption kinetics were best described by the pseudo-first-order and pseudo-second-order models, which revealed that the progress is affected by physical diffusion and chemical sorption. Furthermore, the microscopic characterization results demonstrate that cation exchange reactions and surface complex reactions are the main sorption mechanisms for Sr sorption on claystone. Ca and Mg plasmas in claystone minerals can have cation replacement reactions with Sr, and functional groups such as -OH and [CO3]2− can have complexation reactions with Sr to adsorb Sr on the surface of the claystone. Additionally, the presence of the FeOOH colloid inhibited the sorption effect of claystone slightly. The FeOOH colloid could occupy sorption sites on the claystone surface, which reduces the activity of the functional groups and inhibits the sorption of Sr on claystone.

Sorption of Strontium to Uraninite and Uranium(IV)-Silicate Nanoparticles.

Spent nuclear fuel contains both uranium (U) and high yield fission products, including strontium-90 (90Sr), a key radioactive contaminant at nuclear facilities. Both U and 90Sr will be present where spent nuclear fuel has been processed, including in storage ponds and tanks. However, the interactions between Sr and U phases under ambient conditions are not well understood. Over a pH range of 4–14, we investigate Sr sorption behavior in contact with two nuclear fuel cycle relevant U(IV) phases: nano-uraninite (UO2) and U(IV)–silicate nanoparticles. Nano-UO2 is a product of the anaerobic corrosion of metallic uranium fuel, and UO2 is also the predominant form of U in ceramic fuels. U(IV)–silicates form stable colloids under the neutral to alkaline pH conditions highly relevant to nuclear fuel storage ponds and geodisposal scenarios. In sorption experiments, Sr had the highest affinity for UO2, although significant Sr sorption also occurred to U(IV)–silicate phases at pH ≥ 6. Extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy, and desorption data for the UO2 system suggested that Sr interacted with UO2 via a near surface, highly coordinated complex at pH ≥ 10. EXAFS measurements for the U(IV)–silicate samples showed outer-sphere Sr sorption dominated at acidic and near-neutral pH with intrinsic Sr-silicates forming at pH ≥ 12. These complex interactions of Sr with important U(IV) phases highlight a largely unrecognized control on 90Sr mobility in environments of relevance to spent nuclear fuel management and storage.

Organo-Inorganic Composites Based on Phosphorus Vermiculite and Resorcinol–Formaldehyde Polymer and Their Use for Sorption of Nonradioactive Strontium from Solutions

Organo-Inorganic Composites Based on Phosphorus Vermiculite and Resorcinol–Formaldehyde Polymer and Their Use for Sorption of Nonradioactive Strontium from Solutions

Sorption of lead (II) and strontium (II) ions from aqueous solutions onto non-living Chlorella Vulgaris Alga/ Date pit activated carbon composite

Sorption of lead (II) and strontium (II) ions from aqueous solutions onto non-living Chlorella Vulgaris Alga/ Date pit activated carbon composite

Separation of radiostrontium from seawater using various types of sorbents

The paper presents the results of separating radioactive strontium from seawater with commercially available local-produced sorbents (Modix, FD, MDM, DMM, Termoksid ZK, SRM-Sr) and the sorbent of our fabrication (MnO2–impregnated fiber) under static and dynamic conditions. Under the batch conditions, the distribution coefficients of strontium in seawater are determined. Under the flow conditions, output curves of strontium sorption at different seawater flow rates were obtained; the dynamic exchange capacity and total dynamic exchange capacity of the sorbents for strontium were calculated. The data obtained make it possible to calculate the amount of sorbent required to process a seawater sample of a given volume for determining the specific activity of strontium radionuclides in seawater.

Prediction of batch sorption of barium and strontium from saline water

Celestite and barite formation results in contamination of barium and strontium ions hinder oilfield water purification. Conversion of bio-waste sorbent products deals with a viable, sustainable and clean remediation approach for removing contaminants. Biochar sorbent produced from rice straw was used to remove barium and strontium ions of saline water from petroleum industries. The removal efficiency depends on biochar amount, pH, contact time, temperature, and Ba/Sr concentration ratio. The interactions and effects of these parameters with removal efficiency are multifaceted and nonlinear. We used an artificial neural network (ANN) model to explore the correlation between process variables and sorption responses. The ANN model is more accurate than that of existing kinetic and isotherm equations in assessing barium and strontium removal with adj. R2 values of 0.994 and 0.991, respectively. We developed a standalone user interface to estimate the barium and strontium removal as a function of sorption process parameters. Sensitivity analysis and quantitative estimation were carried out to study individual process variables’ impact on removal efficiency.

Extraction chromatographic materials based on polysulfone microcapsules for the sorption of strontium from aqueous solution

Crown ether-loaded polysulfone (PS) capsules suitable for the separation and preconcentration of strontium from acidic nitrate media have been prepared and characterized. Specifically, PS macro- and microcapsules have been impregnated with the macrocyclic polyether di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6), either undiluted or as a solution in 1-octanol, and their performance in the extraction of strontium from nitric acid solution evaluated. The DtBuCH18C6-loaded microcapsules were found to exhibit strontium uptake efficiency significantly greater than that observed for the analogous macrocapsules, confirming earlier observations of a marked size-dependence of the behavior of extractant-loaded PS capsules. Comparison of the microcapsules to a commercial extraction chromatographic (EXC) material (Sr-resin) comprising DtBuCH18C6-loaded beads of poly(methyl methacrylate) (PMMA) of comparable size (50–100 μm), showed that the two materials exhibit similar strontium retention, uptake kinetics, and selectivity. The microcapsules provide higher column efficiencies, however, and when fully loaded with extractant, higher strontium ion uptake capacity.

Mechanisms of Sorption of Cesium and Strontium by Ferrocyanide-Modified Clinoptilolite at Their High Concentration in Solutions

The kinetics of cesium and strontium sorption by natural clinoptilolite and its ferrocyanide-modified analogs, NPF-Cl and NPF-Cl (Ca-form), from solutions of various compositions containing 100 mg L–1 sorbate was studied, and the texture and porosity of the sorbent samples before and after the sorption of cesium and strontium were determined. The sorption process occurs in three-stages and is limited by a heterogeneous ion exchange reaction (HIOR) on the ferrocyanide phase located on the outer surface of clinoptilolite and in its macropores, internal diffusion of cesium and strontium into sorbent granule, and precipitation of ferrocyanide phases of complex composition in small mesopores and micropores of sorbents. The HIOR and precipitation occur with involvement of solution components (sodium, calcium, and iron). Sorption of cesium and strontium is accompanied by a significant change in the texture and porosity of the sorbents.

Diffusion and Sorption of Radium and Strontium in a Layer of Porous Sorbent Based on Hydroxyapatite

A cell for studying the diffusion of therapeutic medical radionuclides into the macrolayer of the carrier sorbent was fabricated using 3D printing. The diffusion of ultramicroquantities of radium and strontium within a layer of watered hydroxyapatite was investigated. The value of the effective diffusion coefficient obtained using a one-dimensional nonstationary model was (1.0 ± 0.4) × 10–8 cm2/s for Ra and (3.0 ± 0.3) × 10–8 cm2/s for Sr.