Sorption Of Sr Research Articles

Sorption of 90Sr and 137Cs on clays used to build safety barriers in radioactive waste storage facilities

The purpose of the work was to investigate the sorptive capacity of natural clay samples with respect to 90Sr and 137Cs to assess the possibility of using these as components of protective barriers at radioactive waste isolation facilities. Bentonite clays of the Zyryanskoye and Desyaty Khutor deposits and high-melting clay of the Kampanovskoye deposit were selected for the investigation. The capacity of clays for sorption through ionic exchange is characterized by the value of the cation exchange capacity (CEC). In the process of sorption experiments, all of the test clays displayed a high rate of extracting strontium and cesium radionuclides from aqueous solutions. It was shown that the sorption of 90Sr is affected by the content of montmorillonite in the samples: bentonite clays absorb up to 98–99% of the initial radionuclide content in the solution, while about 80% of strontium is sorbed by high-melting clay. Cesium is practically fully sorbed by the tested samples and the degree of sorption amounts to over 99%, the highest value of the distribution coefficient having been recorded for the Kampanovskoye sample (Kd = 5.0×103 cm3/g). The method of sorbed radionuclides fixation on the clay samples were identified by selective desorption using the modified Tessier methodology. It was shown that strontium ions are more mobile than ions of cesium up to 97% of which is retained by clays.

Сорбция 90Sr и 137Cs на глинах, используемых при сооружении барьеров безопасности в хранилищах радиоактивных отходов

Сорбция 90Sr и 137Cs на глинах, используемых при сооружении барьеров безопасности в хранилищах радиоактивных отходов

Efficient separation of strontium radionuclides from high-salinity wastewater by zeolite 4A synthesized from Bayer process liquids

The efficient, selective, and economical sorbents for the removal of Sr radionuclides are largely needed for the decontamination of effluents with high salinity. In this study, the removal of Sr was investigated using the zeolite produced from the Bayer process liquids. Based on the XRD, SEM/EDS analysis, the product was pure and highly crystalline zeolite 4A (Z4A). Removal of Sr was fast (5 min for 100% removal at 8.80 mg/L), with high maximum sorption capacity (252.5 mg/L), and independent on the initial pH in the range 3.5–9.0. Specific sorption of Sr by protonated groups on the Z4A surface was operating in addition to ion-exchange with Na ions. The selectivity of Z4A decreased in the order Sr > Ca > K > Mg > Na. 84% of Sr was separated from seawater within 5 min, at the Z4A dose of 5 g/L, while efficiency increased to 99% using the dose of 20 g/L. Desorption of radioisotope 89Sr from seawater/Z4A solid residue was very low in deionized water (0.1–0.2%) and groundwater (0.7%) during 60 days of leaching. Z4A is a cost-effective, selective, and high-capacity medium for Sr removal, which provides high stability of retained radionuclides.

Surface complexation of Ca and competitive sorption of divalent cations on montmorillonite under alkaline conditions

In the geological disposal system of high-level radioactive and transuranic wastes, an increase in Ca concentration (arising from the alteration of cementitious materials) could affect the retention of other radionuclides due to competitive sorption. Batch sorption experiments were performed to investigate the sorption behavior of Ca and its competition with other divalent cations (Sr and Ni) on the edge sites of Kunipia F montmorillonite under alkaline conditions. Ca sorption increased with pH (when pH > 8) and it was more pronounced under high ionic strength conditions, indicating that Ca formed a surface complexation with the edge sites. The sorption behavior of Sr was similar to that of Ca. Meanwhile, the Ni sorption increased with pH, when this was >6 (for lower pH values than in the case of Ca and Sr), Ni tends to form surface complexes more readily than Ca and Sr. The results of a fitting analysis conducted based on the 2-site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model indicate that Ca and Sr sorb onto the ≡SW2OH sites and Ni sorbs onto the ≡SSOH sites. Additionally, the sorption of the CaOH+ and SrOH+ ionic pair species by cation exchange was implied at pH ~ 12. Competitive sorption experiments were also carried out to evaluate the effect of Ca on the sorption of Sr and Ni. Sr sorption decreased with Ca concentration in the alkaline pH region, whereas Ni sorption was not affected by Ca concentration. Overall, these results indicate that Ca and Sr sorb onto the same sites, while Ca and Ni sorb onto different sites; additionally, the competitive sorption seemed to depend on chemical similarities (e.g., hydrolysis behavior). The sorption model parameters obtained from the single-element batch sorption experiments successfully reproduced the results of the competitive sorption experiments.

Bentonite Rock from Oglanlynski Field (Turkmenistan) and Composites Based on It as Sorbents for 90Sr

Removal of 90Sr from aqueous media by sorbents prepared from bentonite from the Oglanlynski field and by their composites with magnetite is studied. It is shown that the sorbents can be used for purification of large volumes of radioactively contaminated waters. Here, we study bentonite rock material (a natural mineral), montmorillonite in Na-form derived from it, clinoptilolite and cristobalite (impurities in bentonite), and composites obtained by depositing magnetite onto the surface of listed materials. The 90Sr sorption is effective in a broad pH range (3.7–9). The developed composites can be successfully used in purification of radioactively contaminated aquatic environments. The magnetite in sorbents functions exclusively as a magnetically active component, which enables us to use an external magnetic field in separation of sludge resulting from water purification process. The maximum adsorption of strontium ions, as calculated from the Langmuir equation, is obtained for montmorillonite in Na-form and the initial rock material: 20.8 and 14.5 mg/g, respectively. For the composites based on these materials, the values are smaller: 18.5 and 10.6 mg/g, respectively. The effectiveness of sorbents for removal of 90Sr from natural waters and liquid radioactive wastes is shown to be determined mostly by the mineral content of media to be purified, i.e., the type and concentration of macro elements: Na+, K+, and Ca2+. Among the indicated competing ions, calcium affects the removal of strontium from aquatic environments to the largest extent.

Sorption of Sr in granite under typical colloidal action

The sorption behaviour of Sr into granite was studied with the presence or absence of typical colloids (goethite, bentonite and humic acid). A batch technique was used to analyse the influencing process of colloids and key factors. Moreover, scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize granite samples before and after the batch experiments. The experiments showed that the presence of colloids promotes the sorption of Sr in the broken granite system; when goethite, bentonite or humic acid (HA) was present, the sorption capacity percentages were 1.8, 2.13 and 1.93 times higher, respectively, than those in the granite only system. As the initial Sr2+ concentration increased, the sorption of Sr increased, but the sorption percentage decreased; the sorption percentage reached a maximum at pH = 7 and decreased as the acidity or alkalinity of the solution increased. The sorption of granite may be related to the interstitial water of the hydroxyl, quartz, and feldspar, the intergranular water of granite groups and the water molecules attached to the granite. Moreover, the surface of the granite sample was rougher after the sorption experiment.

Controlled bi-functionalization of silica microbeads through grafting of amidoxime/methacrylic acid for Sr(II) enhanced sorption

Silica microspheres are functionalized through the grafting of either polymethacrylic acid or amidoxime groups (mono-functional composite, PMAA/SiO2 and PAO/SiO2, respectively) or in combination (bi-functional composite, PAOxMAA100-x/SiO2). The materials are characterized by textural analysis, TGA, SEM-EDX, elemental analysis, FTIR, XPS, pHPZC in order to confirm the synthesis route, identify the reactive groups and support the interpretation of sorption mechanisms toward Sr(II). The sorption of Sr(II), at optimum pH 8, involves amine groups and hydroxyl/carboxyl groups in the bi-functional composite sorbent. The comparison of sorption properties shows that maximum sorption requires a majority of carboxylic groups from polyacrylic compared with amidoxime functions; optimum formulation: PAO20MAA80/SiO2 sorbent. Sorption isotherms are efficiently fitted by the Langmuir and Sips equations: the maximum sorption capacity reaches around 1.38 mmol Sr g−1. Kinetic profiles for sorption are modeled using the pseudo-first order rate equation; equilibrium is achieved within 40–60 min. Complete desorption of Sr(II) using 1 M HCl solutions is even faster; equilibrium time being 15–20 min. The sorbent can be recycled for 5 cycles with a limited decrease in the sorption performance, and full desorption. In fixed-bed column, the breakthrough curves are fitted by the Thomas equation. In multi-component solutions, the sorbent shows a preferred selectivity according the sequence: K(I) > Ba(II) > Na(I) > Ca(II). Tested on seawater, the sorbent shows high distribution ratio for Sr(II), B(III) and Mo(VI)

Investigation of the surface properties and microstructure of TiO2 sorbents prepared in supercritical CO2 for the treatment of Sr2+ contaminated effluents

Nuclear facilities generate contaminated effluents containing radionuclides (such as Cs, Sr, Co…) that need to be removed for human health and environment protection reasons. Inorganic sorbents are attractive candidate materials because of their high thermochemical and radiation stability. Furthermore, their microstructural and surface properties can be adjusted to increase the radionuclide extraction efficiency. In this study, nanostructured sorbents consisting of aggregated TiO2 nanocrystals with different surface properties and microstructures were prepared in supercritical CO2 by varying the synthesis temperature. The Sr2+ sorption process was characterized by measuring the surface properties and extraction capacity of the samples as a function of pH. In basic effluents, the Sr sorption capacity of these materials is directly linked to their specific surface area and sorption site density through a classic physisorption mechanism. Sr2+ diffusion into the mesopores leads to rapid initial sorption, which is followed by a slower process driven by a proposed multistep mechanism. This mechanism involves the initial adsorption of partially hydrated Sr2+ ions up to complete TiO2 surface coverage, which implies slower Sr ion diffusion due to steric hindrance in small mesopores thus limiting access to additional secondary sites with lower adsorption energies.

Retraction: Mutual effect of Cs(i) and Sr(ii) sorption on nano-talc investigated by EXAFS, modeling and theoretical calculations

Retraction of ‘Mutual effect of Cs(i) and Sr(ii) sorption on nano-talc investigated by EXAFS, modeling and theoretical calculations’ by Yubing Sun et al., Environ. Sci.: Nano, 2019, 6, 672–683.

The influence of thermal processing on the sorption of Cs and Sr by sitinakite

Abstract The remediation of radioactive isotopes such as Cs+ and Sr2+ from water has been evaluated using sitinakites. The sorption media employed in the remediation of radioactive wastes must have thermal and chemical stability to be useful. The present study investigates the structural stability and adsorption performance of sitinakites under conditions of elevated temperatures between 50 and 550 °C. X-ray diffraction indicates that major structural changes are initiated with heating, reducing the crystallinity of the material. The FTIR results also indicate that simultaneous and irreversible dehydration of the materials occurs with elevated temperatures under the conditions studied. Thermal processing also influences the sorption of Cs+, which decreases rapidly as the temperature increases. Adsorption was reduced by 80% at 550 °C for Cs+, when compared to the material processed at 50 °C and neutral pH. In contrast, the sorption of Sr2+ decreases substantially only when the processing temperature reaches 550 °C under the same conditions. In addition, the sorption of Cs+ and Sr2+ follow different trends as functions of pH after thermal treatment. The sorption of Cs+ decreases as a function of increased processing temperature and higher alkalinity. In contrast, the sorption of Sr2+ decreases with thermal processing; however, overall Sr2+ sorption increases as the pH becomes more alkaline. The sorption differences suggest that Cs+ uptake is structurally driven, while Sr2+ sorption is influenced by both the structure and the surface electrostatics of the material. These results suggest the effectiveness of the materials may be compromised due to changes in structure, hydration, and electrostatic interactions that occur when exposed to elevated temperatures.

Utilization of Modified Attapulgite for the Removal of Sr(II), Co(II), and Ni(II) Ions from Multicomponent System, Part I: Kinetic Studies.

Radionuclide sorption by natural and modified clays is extensively accepted to be an important process from the radioactive waste point of view. This work focused on modification of natural attapulgite with a layered double hydroxide to produce a novel chemisorbent for Sr2+, Ni2+, and Co2+ removal from multicomponent solution. The structural and surface characteristics of both attapulgite (ATP) and modified attapulgite (LDH-ATP) were investigated using XRD, FTIR, SEM, and thermal analysis. Comparison of sorption features of Sr2+, Ni2+, and Co2+ onto ATP and LDH-ATP was achieved; the results indicated that LDH-ATP was the most efficient sorbent for Sr2+, Ni2+, and Co2+. Kinetic studies established that the sorption is fast and reaching >90% within 30 min. The sorption of Sr2+, Ni2+, and Co2+ are well defined by non-linear pseudo-second-order model and controlled by an intra-particle diffusion mechanism. The diffusivity was determined using homogeneous surface diffusion (HSDM) model and found in the order 10-13 m2/min; this confirmed that the sorption of the three ions is chemisorption process. LDH-ATP can be employed as a candidate chemisorbent for the removal of some metal ions from waste solution.

Сорбция тяжелых металлов на клиноптилолит, модифицированном полиэтиленимином, из слабокислых сред

Методом динамических выходных кривых изучена кинетика сорбции тяжелых металлов(ТМ): Cr, Ni, Cu, Zn, Sr, Cd, Pb, а также макрокомпонентов H+, К+, Ca2+ из поверхностной воды с рН3.7 на модифицированном ПЭИ–КЛТ при совместном присутствии компонентов и низких концентрациях ТМ в исследуемом растворе (0.3-1.5 мг/дм3). Рассчитаны значения сорбционных характеристик(коэффициенты распределения и кинетические характеристики). На примере Н+, Cu, Cr показана возможность расчета динамики сорбции на ПЭИ–КЛТ из поверхностной воды с рН 3.7.

Sorption of Strontium Ions on Barium Silicates from Solutions of Complex Salt Composition

The comparative analysis of sorption properties of nanostructured barium silicates obtained in multicomponent systems BaCl2 · 2H2O–КОН–SiO2–H2O and BaCl2 · 2H2O–КОН–SiO2–AlCl3–H2O has been performed to extend previous data; the data on the composition and morphology of the systems have been presented. Their properties toward sorption of Sr2+ ions from solutions of complex ionic composition have been studied. It has been found that synthetic barium silicates and alumosilicates have high sorption and kinetic characteristics under static sorption conditions. The maximal degree of Sr2+ ions recovery from solutions of complex composition (>99%) was achieved for barium silicate BaSiO3 · 2.3H2O. The samples of barium alumosilicate BaAl2Si2O8 · 2.6H2O have the same sorption characteristics within measurement error. It has been shown that the studied sorbents, allowing for their kinetic properties, may be recommended for the deep purification of solutions of complex ionic composition, seawater including, from strontium ions under static conditions.

Use of rice straw-based biochar for batch sorption of barium/strontium from saline water: Protection against scale formation in petroleum/desalination industries

The formation of hard mineral scale deposits (e.g., celestite (SrSO4) and barite (BaSO4)) is the most common problem that hinders sustainable operations of water-flooded oilfield and desalination systems (i.e., membrane fouling) when using poor quality water contaminated with barium (Ba(II)) and strontium (Sr(II)) ions. In this work, nanoscale biochar (∼53–712 nm) was synthesized from waste rice straw (cost = 380 to 560 ± 27 US$/Ton; n = 9) and applied as a protective approach against the formation of mineral scale deposits via adsorptive removal of Ba(II)/Sr(II) contaminants from 30,000 ppm saline wastewater. Adsorption of Ba(II)/Sr(II) ions onto biochar was investigated and optimized as a function of biochar amount, water pH, contact time, temperature, and Sr(II)/Ba(II) ratio using response surface methodology. Based on kinetic and isotherm analyses, the biochar exhibited enhanced potential to capture Sr(II)/Ba(II) ions via weak ion-exchange or pore-filling mechanisms (sorption energy (E)≈ 0.61–0.89 kJ/mol). A comparison of partition coefficient (PC) values verified that sorption of Sr(II) onto biochar is far superior to that of Ba(II) (PCs of 10.1 and 2.5 μmol g−1 μM−1, respectively). Sorption selectivity was mainly dependent on solution pH and the metallic properties of Ba(II)/Sr(II)(e.g., metal size, speciation, and mobility). Quantitative analysis of treated saline water using electrical conductivity and ion chromatography confirmed the ability of biochar sorbent to remove Ba(II) and Sr(II) ions (97.5%) with pre-desalination (e.g., total salts reduction of 25.7% after 48 h). It is thus recommended to utilize the prepared biochar as a promising pre-desalinating adsorptive medium to inhibit mineral scale formation before oilfield water flooding in the petroleum field and membrane desalination systems.

Sorption and desorption of Sr onto a rough single fractured granite

To investigate the migration behavior of Sr (strontium) in granite, a rough-walled single fracture of granite was prepared with the self-built rock splitting apparatus. Surface roughness angle and hydraulic aperture of the fracture were measured by 3D laser scanning and fluid flow experiment, respectively. The sorption and desorption breakthrough experiments of Sr in the single fracture were conducted at different flow rates and initial concentrates of Sr, and the important transport parameters were derived by fitting the BTCs and DPCs. The results suggested that the sorption of Sr onto the fracture surface was a linear and reversible ion-exchange process, unaffected by the variation of flow rate and initial concentrate of Sr.

Sorption of 90Sr onto Manganese Oxides Prepared in Aqueous-Ethanol Media

Sorbents based on manganese oxides were prepared by KMnO4 reduction in aqueous-ethanol medium. The influence of the synthesis conditions (temperature and time of the sol-gel synthesis, type of structure-forming cations, calcination temperature) on the pore structure and on the performance and selectivity in 90Sr sorption was studied. The sorbents have the mesoporous structure with the specific surface area of 180–220 m2 g−1 and mean pore size of 10–20 nm. Manganese oxide of channel structure in the Na+ form, prepared by the reaction at 25°C for 5 h and heat-treated at 350°C, exhibits the highest performance and selectivity in 90Sr sorption (distribution coefficient Kd = 1.04 × 104 cm3 g−1, Sr-Ca separation factor DSr/Ca = 99). The sorbents synthesized exhibit the highest performance and selectivity in neutral and alkaline media.

Sorption of Strontium and Lead by Impregnated Sorbents Based on Di(tert-butylcyclohexano)-18-crown-6 and an Ionic Liquid

Sorption of Sr(II) and Pb(II) onto impregnated sorbents based on di(tert-butylcyclohexano)-18-crown-6 and an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C4mim+Tf2N−), was studied. The influence of the crown ether concentration in the sorbent, kind and pretreatment of the support, and kind of the solvent used for impregnation on the sorption of Sr and Pb onto sorbents based on di(tert-butylcyclohexano)-18-crown-6 and C4mim+Tf2N− was analyzed. Sr(II) is taken up most efficiently from neutral and weakyl acidic (up to 0.01 M HNO3) media with the degree of sorption R > 90% and distribution coefficients Kd from 1410 to 706 cm3 g−1, respectively. The efficiency of the Sr(II) sorption is not affected by Na+ ions in the solution up to their concentration of 1 M. In the presence of calcium ions, as the Ca(II) concentration in the solution is increased from 0.02 to 0.16 M, Kd of Sr(II) decreases by a factor of 4. In sorption of 90Sr from seawater, Kd is 193 cm3 g−1; it increases by a factor of 1.05 and 1.25 upon dilution of seawater by a factor of 2 and 10, respectively. Lead(II) is quantitatively taken up from neutral media (R > 98%) and from 0.01–1.0 M HCl and 0.01–3.0 M HNO3 solutions (R > 87%). The sorbents prepared show promise for radioanalytical determination of Sr and Pb radionuclides in natural objects.

Amidoxime Functionalization of Algal/Polyethyleneimine Beads for the Sorption of Sr(II) from Aqueous Solutions.

There is a need for developing new sorbents that incorporate renewable resources for the treatment of metal-containing solutions. Algal-polyethyleneimine beads (APEI) (reinforced with alginate) are functionalized by grafting amidoxime groups (AO-APEI). Physicochemical characteristics of the new material are characterized using FTIR, XPS, TGA, SEM, SEM-EDX, and BET. AO-APEI beads are tested for the recovery of Sr(II) from synthetic solutions after pH optimization (≈ pH 6). Uptake kinetics is fast (equilibrium ≈ 60–90 min). Sorption isotherm (fitted by the Langmuir equation) shows remarkable sorption capacity (≈ 189 mg Sr g−1). Sr(II) is desorbed using 0.2 M HCl/0.5 M CaCl2 solution; sorbent recycling over five cycles shows high stability in terms of sorption/desorption performances. The presence of competitor cations is studied in relation to the pH; the selectivity for Sr(II) is correlated to the softness parameter. Finally, the recovery of Sr(II) is carried out in complex solutions (seawater samples): AO-APEI is remarkably selective over highly concentrated metal cations such as Na(I), K(I), Mg(II), and Ca(II), with weaker selectivity over B(I) and As(V). AO-APEI appears to be a promising material for selective recovery of strontium from complex solutions (including seawater).

Effect of Colloidal Silicate on the Migration Behaviour of Strontium in Groundwater Environment of Geological Disposal Candidate Site

Various colloids are present in the natural groundwater environment, and colloids act on the processes involved when radionuclides leak from a repository in a high-level waste disposal site. This paper investigates the effect of colloidal silicate in natural groundwater environments on the migration behaviour of Sr(II). Three different experimental cases have been designed: (1) effect in the presence of colloidal silicate, (2) effect in the presence of a porous medium, and (3) effect in the presence of both colloidal silicate and porous medium (referred to as CS, PM, and PC, respectively). Batch experiments were used to study the effect of influencing factors on Sr(II) migration behaviour, such as the amount of CS, solid-to-liquid ratio, pH, contact time, and initial concentration of Sr(II). The experiments showed that the effect of PC on the migration behaviour of Sr(II) was greatest, and the presence of CS enhanced the sorption. The colloid amount, pH, and solid-to-liquid ratio significantly affected the migration behaviour. The more the colloids were added, the better the adsorption effect. The optimal pH and solid-to-liquid ratio were 6 and 20 : 1, respectively. The alkaline environment is more conductive to colloid sorption. When the solid-to-liquid ratio was 20 : 1, the sorption percentage of PC is 0.5 times larger than PM. Although the PC has a longer adsorption equilibrium time, the percentage of adsorption can be larger than that in the other two cases. The kinetics and isotherms of Sr(II) were best described by the pseudo-second-order and Langmuir models. It was inferred that strong chemical interactions and/or surface complexation contributed primarily to Sr(II) sorption, and the process was on the monolayer adsorption of the outer surface. These findings provide valuable information for the migration behaviour of strontium in groundwater environments of geological disposal site. At the same time, it provides information for the implementation of permeable reactive barrier technology to control the transport of radioactive Sr(II) and its species in natural surface and groundwater.

Effect of a humic acid colloid on the sorption behaviour of Sr onto soil in a candidate high-level radioactive waste geological disposal site

We explored the effect of the presence or absence of humic acid (HA) on the sorption behaviour of Sr onto soil. We examined three different experimental cases for Sr sorption: (1) sorption in the presence of only colloidal HA, (2) sorption in the presence of only soil and (3) sorption in the presence of both colloidal HA and soil (HS). A batch technique was used to study the influencing factors, including the amount of colloidal HA, solid content, pH, initial concentration of Sr and contact time. The experiments showed that the influencing factors significantly affected the sorption process. For example, in the case of soil and HS, the sorption percentage increased rapidly with increasing solid content at m/V < 20g/L, changing from 8.35% and 37.54% to 49.09% and 77.03%, respectively. Moreover, scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize samples. The kinetics and isotherms of Sr were best described by the pseudo-second-order and Langmuir models, which indicated that the process was controlled by chemisorption and uniform monolayer sorption with constant energy on the outer surface. These findings provide valuable information for predicting strontium migration in radioactive waste disposal sites.