Sorption Of Strontium Research Articles

Investigation of Strontium (II) Sorption Kinetic and Thermodynamic onto Straw-derived Biochar

Biochars have attracted much research attention recently because of their potential applications in many environmental areas. In this study, rice straw-derived biochars produced at different pyrolysis temperatures (550–750°C) were used as adsorbents for the removal of strontium (II) under different experimental conditions of time, pH, and temperature. Sr(II) sorption equilibrium occurs after 30 min and its sorption maximum achieved at pH 6. The kinetic data obtained were analyzed to predict the constant rate of sorption using three common kinetic models: pseudo-first-order, pseudo-second-order equation, and intraparticle diffusion equation. The pseudo-second-order model was suitable for describing the sorption kinetics for the removal of Sr(II) from aqueous solution onto straw-derived biochar. Sorption of Sr(II) onto biochar was endothermic. Biochar has the highest Sr(II) sorption capacity in comparison to other adsorbents.

Study on sorption and diffusion of Sr in crushed and intact basalt and granite investigated in through-diffusion experiments

This study investigates sorption and diffusion of strontium (Sr) in two potential host rocks (granite from Kingman Island and basalt from Penghu Island) by using batch and column methods. According to solid-phase analysis, the sorption component primarily contained iron–magnesium (Fe–Mg) minerals in basalt and granite. Moreover, the distribution coefficient (K d) of Sr in various concentrations obtained from batch tests indicated a higher sorption capacity in basalt than that in granite because of the 10 % Fe–Mg mineral content. According to the diffusive results in crushed and intact rocks, it showed that major retardation of Sr depended on the micro-porous structure of tested media, such as decreases of constrictivity and increases of tortuosity.

Sorption of strontium by the endoreceptor dibenzo-18-crown-6 immobilized in a polymer matrix

A set of new sorbent were obtained by impregnation different amounts of endoreceptor dibenzo-18-crown-6 in the styrene–divinylbenzene polymer matrix “Porolas-T”. Physical and chemical parameters of strontium sorption on a natural mixture of isotopes from nitric acid solutions were investigated, namely isotherm of sorption, dependence of the distribution coefficient on the concentration of nitric acid in a solution and concentration of crown ether in the sorbent, kinetics of sorption and desorption of strontium. The selectivity of strontium sorption was studied to the alkaline, alkaline-earth metals and cobalt. The sorption properties of sorbent were examined to extraction of radioactive 90Sr.

Sorption of strontium and yttrium radionuclides from aqueous solutions onto layered double hydroxides of various compositions

New experimental results and published data on sorption of strontium and yttrium radionuclides from aqueous solutions onto layered double hydroxides (LDHs) of various compositions are summarized. The effect of double-charged (Mg2+, Ba2+, Sr2+, Cu2+, Zn2+, Ni2+) and triple-charged (Al3+, Fe3+, Nd3+) cations incorporated in the LDH matrix and of anions incorporated in LDH (CO32−, SO42−, NO3−, OH−, Cl−, C2O42−, H2EDTA2−) on the physicochemical properties of this class of compounds, including the ability to sorb strontium and yttrium radionuclides, is examined.

Studies of strontium(II) sorption on soil samples in the presence of phosphate ions

Studies of 90Sr migration in soil systems require determination of some factors affecting this process. One of the most important factors is sorption of strontium cation in the presence of other ions. The paper presents the õstudies on Sr (II) sorption in the presence of phosphate ions in the solution. It was found that under the study cations at pH (3–10) in the presence of phosphate cation sorption increases depending on the soil type. The isotherms can be described by Freundlich equation.

Effect of γ-ray radiation on the biosorption of strontium ions to baker’s yeast

Radionuclide remediation is becoming an increasingly serious environmental problem, posing threat to biotic life. Biosorption is a technology for the treatment of wastewater containing metal ions. In this work, the biosorption of strontium ions (Sr2+) to baker’s yeast and the effect of γ-ray radiation on the biosorption process were investigated at different experimental conditions. The experimental results fitted well to the Langmuir and Freundlich model isotherms before and after the γ-ray radiation (r2 > 0.985), and the maximum biosorption capacity values were qmax > 33.0 mg g−1 at 30 °C. Negative values of ΔG0 and positive values of ΔH0 were observed indicating, the spontaneous and endothermic nature of Sr2+ biosorption on baker’s yeast, respectively. The biosorption kinetics followed a pseudo-second-order equation at different experimental temperatures (r2 > 0.999), the calculate results of the strontium sorption capacity at equilibrium (qe,cal) increased about 0.4–1.0 mg g−1 after γ-ray irradiated. The activation energy of baker’s yeast biosorption to Sr2+ decreased 0.79 kJ mol−1 after γ-ray radiation. The γ-ray radiation affects the amide bands of proteins and leads to a decrease of the isoelectric point from pH of 2.55 to 2.25 and an increase in the electronegativity of the cells wall. In summary, an appropriate γ-ray radiation condition not only has no negative effects, but also can enhance its biosorption capacity slightly of Sr2+ to baker’s yeast.

Investigation of strontium and uranium sorption onto zirconium-antimony oxide/polyacrylonitrile (Zr-Sb oxide/PAN) composite using experimental design

A study on the sorption of strontium (Sr2+) and uranium (UO22+) onto zirconium-antimony oxide/PAN (Zr-Sb oxide/PAN) composite was conducted. The zirconium-antimony oxide was synthesized and was then turned into composite spheres by mixing it with polyacrylonitrile (PAN). The single and combined effects of independent variables such as initial pH, temperature, initial ion concentration and contact time on the sorption of Sr2+ and UO22+ were separately analyzed using response surface methodology (RSM). Central composite design (CCD) was separately employed for Sr2+ and UO22+ sorption. Analysis of variance (ANOVA) revealed that all of the single effects found statistically significant on the sorption of Sr2+ and UO22+. Probability F-values (F=2.45×10−08 and F=9.63×10−12 for Sr2+ and UO22+, respectively) and correlation coefficients (R2=0.96 for Sr2+ and R2=0.98 for UO22+) indicate that both models fit the experimental data well. At optimum sorption conditions Sr2+ and UO22+ sorption capacities of the composite were found as 39.78 and 60.66mg/g, respectively. Sorption isotherm data pointed out that Langmuir model is more suitable for the Sr2+ sorption, whereas the sorption of UO22+ was correlated well with the Langmuir and Freundlich models. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° indicate that Sr2+ and UO22+ sorption processes are endothermic and spontaneous.

Adsorption of Strontium from Aqueous Solution Using Collagen Fiber Immobilized Tannins

The removal of strontium from aqueous solution with collagen fiber immobilized tannins was studied. The effects of several experimental parameters such as pH, dosage, temperature, contact time and initial concentration of strontium on removal efficiency of strontium were investigated to determine the optimum conditions of strontium sorption process. The adsorbent was characterized by SEM and FTIR analysis. The results of regression analysis indicated that temperature parameters were not individually statistically significant for Sr2+ adsorption. However, the efficiency of strontium adsorption increased with the increase in pH and dosage. The adsorption capacity was increased with increasing initial concentration of Sr2+. The removal efficiency of Sr2+ was 49% at optimum pH of 6 and initial concentration of 20mg/L. Moreover, the absorption data were fitted well to the Langmuir sorption isotherm model.

Sorption and retardation of strontium in saturated Chinese loess: experimental results and model analysis

Geological burial and landfill have been widely practiced for disposal of nuclear wastes. However, radionuclides in the waste leachate from landfill facilities can contaminate soil and groundwater. Chinese loess is widely distributed in China and has been involved in large-scale disposal of nuclear wastes. Consequently, there has been an urgent need for understanding and predicting the fate and transport of contaminants in both vadose and saturated zones in the loess. In this paper, the distribution coefficient (Kd) values of Strontium between a Chinese loess and groundwater were determined in batch experiments. The isotherm could be described with nearly linear isotherm model, which resulted in a Kd value of 40.0 cm3/g. Based on this Kd value, the retardation factor (Rd, the ratio of pore water velocity to solute transport velocity) value was calculated to be 112.6. As an alternative approach, the Rd value was also determined through independent column experiments and transport modeling. Bromide (Br−) was used as a non-reactive tracer, and reagent SrCl2 was used as a surrogate for the radioactive isotope (99Sr) in the experiment because they share the same adsorption and transportation characteristics. An equilibrium-based model and a two-region non-equilibrium model were employed to interpret the column sorption data of Sr. The computer program, CXTFIT 2.1, was used to estimate the parameters by simulating the breakthrough and retention curves of Br and Sr, respectively. The resultant D (dispersion coefficient) value for Sr transport was much lower than that of Br−, indicating the important effect of chemical non-equilibrium of Sr in the loess system. The observed Sr retention curves in the loess were best modeled by the two-site transport model. The Rd value determined from batch equilibrium tests differed markedly from that determined from the column transport experiments, and the Rd value decreased with increasing pore-water velocity. The relationship between D and pore water flow velocity (v) was determined as a D = 1.192v1.26. The results from this work indicate that the strong flow and non-equilibrium effects on the transport parameters (Rd and D) must be taken into account in Sr transport modeling.

Strontium sorption by pectins isolated from the Sea grasses Zostera marina and Phyllospadix iwatensis

In this study, we determined the parameters of sorption of strontium ions by pectins that were isolated from the sea grasses Zostera marina and Phyllospadix iwatensis collected in the Peter the Great Bay of the Sea of Japan. The maximum strontium binding capacity and the coefficient of affinity with respect to strontium ions were significantly higher in sea grass pectins than in commercial pectin. These parameters were correlated with the etherification degree of pectins. The sea grasses studied here can be considered as a promising source of pectins for the binding and removal of strontium radioisotopes from the human body.

Adsorption of strontium from aqueous solution using activated carbon produced from textile sewage sludges

Different types of activated carbons were prepared by changing the activation temperatures (400–700°C) and impregnation ratio (sewage sludge: KOH; 1:1, 1:2) and the removal of Sr+2 from aqueous solution was determined. The maximum adsorption yield (12.11mg/g) was obtained at 500°C for 1h carbonization conditions with impregnation ratio of 1:1. The affecting parameters were analyzed by using central composite design method. The selected parameters were initial pH, temperature, initial strontium concentration and carbon dosage. The analysis of variance was performed in 95% confidence level and checked to fitting of experimental value and predicted value. The significant F was P<0.05 with a model F value of 19.94 which revealed that this regression is statistically significant. The results of regression analysis indicated that pH and temperature parameters were not individually statistically significant for Sr+2sorption. However, the efficiency of strontium sorption increases with the increase in carbon dosage and decreases with the Sr+2 concentration. Influences of initial pH and temperature, pH and Sr+2 concentration, temperature and carbon dosage and Sr+2 concentration and carbon dosage on the adsorption process were considered statistically significant. Adsorption of strontium was described by Freundlich isotherm as a physical adsorption (E=7.2kJ/mol). The adsorption reactions were calculated as endothermic, spontaneous and favorable reactions.

Effect of groundwater pH and ionic strength on strontium sorption in aquifer sediments: Implications for 90Sr mobility at contaminated nuclear sites

Abstract Strontium-90 is a beta emitting radionuclide produced during nuclear fission, and is a problem contaminant at many nuclear facilities. Transport of 90 Sr in groundwaters is primarily controlled by sorption reactions with aquifer sediments. The extent of sorption is controlled by the geochemistry of the groundwater and sediment mineralogy. Here, batch sorption experiments were used to examine the sorption behaviour of 90 Sr in sediment–water systems representative of the UK Sellafield nuclear site based on groundwater and contaminant fluid compositions. In experiments with low ionic strength groundwaters ( −1 ), pH variation is the main control on sorption. The sorption edge for 90 Sr was observed between pH 4 and 6 with maximum sorption occurring ( K d ∼ 10 3 L kg −1 ) at pH 6–8. At ionic strengths above 10 mmol L −1 , and at pH values between 6 and 8, cation exchange processes reduced 90 Sr uptake to the sediment. This exchange process explains the lower 90 Sr sorption ( K d ∼ 40 L kg −1 ) in the presence of artificial Magnox tank liquor (IS = 29 mmol L −1 ). Strontium K-edge EXAFS spectra collected from sediments incubated with Sr 2+ in either HCO 3 -buffered groundwater or artificial Magnox tank liquor, revealed a coordination environment of ∼9 O atoms at 2.58–2.61 A after 10 days. This is equivalent to the Sr 2+ hydration sphere for the aqueous ion and indicates that Sr occurs primarily in outer sphere sorption complexes. No change was observed in the Sr sorption environment with EXAFS analysis after 365 days incubation. Sequential extractions performed on sediments after 365 days also found that ∼80% of solid associated 90 Sr was exchangeable with 1 M MgCl 2 in all experiments. These results suggest that over long periods, 90 Sr in contaminated sediments will remain primarily in weakly bound surface complexes. Therefore, if groundwater ionic strength increases (e.g. by saline intrusion related to sea level rise or by design during site remediation) then substantial remobilisation of 90 Sr is to be expected.

Strontium sorption and precipitation behaviour during bioreduction in nitrate impacted sediments

The behaviour of strontium (Sr2+) during microbial reduction in nitrate impacted sediments was investigated in sediment microcosm experiments relevant to nuclear sites. Although Sr2+ is not expected to be influenced directly by redox state, bioreduction of nitrate caused reduced Sr2+ solubility due to an increase in pH during bioreduction and denitrification. Sr2+ removal was greatest in systems with the highest initial nitrate loading and consequently more alkaline conditions at the end of denitrification. After denitrification, a limited re-release of Sr2+ back into solution occurred coincident with the onset of metal (Mn(IV) and Fe(III)) reduction which caused minor pH changes in all microcosms with the exception of the bicarbonate buffered system with initial nitrate of 100mM and final pH>9. In this system ~95% of Sr2+ remained associated with the sediment throughout the progression of bioreduction. Analysis of this pH 9 system using X-ray absorption spectroscopy (XAS) and electron microscopy coupled to thermodynamic modelling showed that Sr2+ became partially incorporated within carbonate phases which were formed at higher pH. This is in contrast to all other systems where final pH was <9, here XAS analysis showed that outer sphere Sr2+ sorption predominated. These results provide novel insight into the likely environmental fate of the significant radioactive contaminant, 90Sr, during changes in sediment biogeochemistry induced by bioreduction in nitrate impacted nuclear contaminated environments.

Sorption of Nuclear Waste Components by Layered Hydrazinium Titanate: a Straightforward Route to Durable Ceramic Forms

ABSTRACTLayered hydrazinium titanate LHT-9, (N2H5)1/2Ti1.87O4 is a new nanohybrid material related to lepidocrocite-type titanates. Unique combination of ion exchange, reductive properties, surface activity due to Brønsted acid sites and occurrence of surface titanyl groups allows exploring LHT-9 for simultaneous uptake of almost all components of liquid nuclear wastes. LHT-9 irreversibly removes technetium, molybdenum, palladium and selenium from their aqueous solutions by specific mechanism of reductive adsorption. For removal of cesium, strontium, transition elements, actinides and lanthanides LHT-9 provides mechanisms of ion exchange and surface complexation. Products of adsorption are nanocrystalline and homogeneous powders loaded with 5 to 15 wt. % of radionuclides and non-radioactive elements. LHT-9 can be applied as ready-to-use precursor for one-step synthesis of durable titanate ceramic waste forms similar to SYNROC. An essential advantage of LHT-9 in comparison with other titanate sorbents (monosodium titanate and peroxo-titanate materials) is the absence of Na in its composition that permits arbitrary tailoring of sorbent properties by simple pre-treatment with the desired elements. Results on sorption of americium, cesium, strontium and lanthanides by LHT-9 are discussed.

Strontium(II) sorption by complexing o-hydroxy-azo-o’-hydroxy functionalized polystyrene polymer sorbents

Optimal parameters for strontium(II) complexing and sorption from aqueous solutions by sorbents based on styrene/divinylbenzene copolymers functionalized with a complexing o-hydroxy-azo-o-hydroxy functionality have been studied, namely, pHopt, 50% sorption pH (pH50), and the time and temperature of quantitative strontium(II) sorption. Strontium(II) sorption capacities have been determined for the sorbents under study; sorption isotherms have been constructed. For a complex formed with polystyrene-o-hydroxy-azo-o’-hydroxy-sulfobenzene, which is an efficient sorbent, the structure has been determined.

Investigation of strontium sorption onto Kula volcanics using Central Composite Design

In performance assessment studies, the uptake of the radioactive elements by rock formations play an important role in retarding their aqueous phase migration. Sorption studies of radionuclides have been conducted to obtain data on the distribution coefficient ( K d) that is as an input parameter in the performance assessment of the geological disposal of radioactive wastes. In this work, sorption experiments were studied in a batch sorption system using Sr(NO 3) 2 solution on non-treated and HCl-treated Kula volcanics. The distribution coefficient ( K d) values of Sr 2+ derived from batch experiments were used to evaluate the migration behavior of Sr 2+. Central Composite Design was used in the experiments. Sr sorption was studied as a function of pH, temperature, initial concentration of adsorbate and contact time. The results show that the K d values are higher at pH 7–9 which is the pH range of the natural waters. The kinetic data conformed better to the pseudo-second-order equation. Thermodynamic parameters Δ H°, Δ S° and Δ G° were estimated and these parameters show that adsorption is endothermic. The correlation coefficients indicate that the Langmuir model fits better for the strontium sorption onto non-treated and HCl-treated Kula volcanics with monolayer capacities as 2.04 and 1.72 mg/g, respectively.

Dust in HTRs: Its nature and improving prediction of its resuspension

The HTR primary-system environment comprises nuclear graphites, alloys, dust (primarily carbonaceous) and high-purity helium. The amount of carbonaceous dust produced in a pebble-bed system would be considerably greater than one using a prismatic core with a significant contribution arising from the partially-graphitized binder of the pebbles. The dust is very fine, <10μm in size. Experience with HTRs shows the primary system to be contaminated by the isotopes 134Cs, 137Cs, 90Sr, 110mAg, 131I, 135Xe, 85Kr and tritium at a level representing an occupational-health issue rather than a safety issue. However, strong sorption of caesium, strontium, iodine and tritium onto carbonaceous dust has been observed. Hence, the extent to which deposited dust can be resuspended during a depressurization accident is a safety issue since the dust comprises the main vector for release of radioactivity into the confinement. For fine dust on a surface, the principal force keeping it in place arises from inter-molecular (van der Waals) forces while aerodynamic forces, mainly drag, act to remove it. The reference model chosen here for improving resuspension predictions is the so-called Rock’n’Roll model. This model is based on a statistical approach leading to a resuspension rate for the escape of particles from a potential well via the action of the fluctuating aerodynamic force caused by turbulence. The as-published Rock’n’Roll model assumes that the fluctuations of the aerodynamic force obey a Gaussian distribution. Here, we introduce calculated statistics for the fluctuations taken from a large-eddy simulation of turbulent channel flow (work is in progress on generating these statistics using direct numerical simulation of turbulence). The overall influence of more-realistic (non-Gaussian) forces on the resuspension rate is found to be an increase in short-term resuspension. Given this and the fact that the adhesive force is based on an empirical correlation, work has started on developing specific modelling for multi-layer deposits.

Geochemical and thermodynamic aspects of sorption of strontium on kaolinite dominated clay samples at Kalpakkam

The mobility of strontium in subsurface is largely influenced by sorption on to clay minerals. In the present study, kaolinite clay samples collected from the Kalpakkam nuclear plant site were employed to understand the sorption characteristics of strontium by batch method. The effect of several parameters such as time, strontium ion concentration, pH, temperature and ionic strength was investigated. The kinetic studies suggested pseudo-second-order mechanism. The experimental sorption data was fitted to Langmuir adsorption model for obtaining the sorption capacity of the sorbent. The maximum sorption capacity was 5.77 mg/g at 298 K and was found to increase with an increase in temperature. It was observed that the distribution coefficient (K d) of strontium on clay increased as the pH of the solution increased. The distribution coefficient was found to decrease with an increase in concentration of Na+ and Ca2+ ions. This variation of K d suggests that cation exchange is the predominant sorption process. It was also observed that sorption process is endothermic. The thermodynamic parameters such as ∆G 0, ∆H 0 and ∆S 0 were calculated. The negative values obtained for ∆G 0 indicated that the sorption of strontium on clay was spontaneous at all studied concentrations. ∆G 0 becomes more negative with an increase in temperature, suggests that the sorption process is more favorable at higher temperatures.

Distribution of strontium in milk component

The distribution of strontium between the milk components, i.e., serum, casein micelles, whey and hydroxyapatite was determined. The sorption on hydroxyapatite was investigated using batch method and radiotracer technique. The aqueous phase comprised of either milk or whey. The sorption of strontium on hydroxyapatite depended on the method of its preparation and on the composition of the aqueous phase. The sorption of strontium was increased with an increase of pH. The presence of citrate species resulted in decrease of the sorption of strontium on hydroxyapatite. The sorption of 85Sr on hydroxyapatite decreased with the increasing concentration of Ca2+ ions. Addition of Ca2+ ions to milk resulted in milk pH decrease. The decrease in pH value after calcium addition to milk is related to exchanges between added calcium and micellar H+. The average value of strontium sorption on casein micelles in milk with presence of hydroxyapatite was (47.3 ± 5.6) %. The average value of sorption of 85Sr on casein micelles in milk without the addition of hydroxyapatite was (68.9 ± 2.2) %.

Retention of Iodide by Bacteriogenic Iron Oxides

This study was performed to determine the ability of wetland bacteriogenic iron oxides (BIOS) to immobilize iodide in contaminated groundwater systems near Chalk River, Canada. The sorption of iodide onto synthetic hydrous ferric oxide (HFO) and BIOS was investigated using an autotitrator and an I− ion-selective electrode to generate high-resolution anion sorption data over a pH range of 2.5 to 9. The effect of strontium sorption in the presence of I− was also investigated to determine its effect on iodide retention as it is also a common contaminant near Chalk River. Both HFO and BIOS correspond to 2-line ferrihydrite with surface areas of 227.7 m2 g−1 and 92.52 m2 g−1, respectively. Sorption of I− was found to be pH dependent for both HFO and BIOS and was most strongly immobilized at pH 2.5. The pH at which 50% of the I− was bound to HFO occurred at pH 4.0, whereas BIOS maintained 50% sorption to pH 9. Field data also indicated a 54% decrease for iodine and 75% for 129I in waters passing over in-situ BIOS at circumneutral pH. Iodide sorption to HFO is best explained by homogeneous functional groups, whereas sorption of I− to BIOS is best explained by heterogeneous functional groups, due to the presence of bacterial functional groups with pKa values that extend to 9.0. The presence of Sr2+ decreased iodide sorption on HFO by 10–20%, but had no effect on BIOS due to its surface functional groups being reactive over the pH range investigated in this study. These results imply that BIOS is a useful sorbent for natural retention of I− from groundwater and that the amount of organic material present in iron oxides is an important factor when considering remediation strategies for radionuclides in groundwater.