Removal Of Strontium Research Articles

Composite Magnetic Sorbents Based on Iron Oxides in Different Polymer Matrices: Comparison and Application for Removal of Strontium.

Introduction of magnetic nanoparticles into composite sorbents based on polymer matrices has received great attention due to the possibility of using cheap iron oxides and removing spent sorbents by means of magnetic separation. In the present paper, we discuss the problem of creating magnetic sorbents using two types of matrices as host materials: synthetic cation exchange resin and natural aminopolysaccharide chitosan. The possibilities of applying matrices for the in situ formation of oxide phases of a specified composition with the required content of an inorganic component in a composite material were estimated. The composition of the oxide phase formed in the composite material was studied, and particle sizes were evaluated by the method of X-ray diffraction analysis. Magnetic characteristics were investigated. Sorption characteristics with respect to strontium for the composites containing iron oxides were determined.

In situ electrochemical synthesis of Zn-Al layered double hydroxides for removal of strontium

In situ electrochemical synthesis method of Zn-Al layered double hydroxides (LDHs) was used to treat the simulated strontium containing liquid radioactive waste (LRW) from nuclear power plants. The removal rate of strontium can reach 98.48±0.20 % (the adsorption capacity is 0.45 mg/g) under the optimal experimental conditions of reaction temperature of 60 °C, reaction time of 240 min, Al electrode current density of 45 mA/cm2, Zn/Al current ratio of 3:1 and initial pH of 10. The composite samples were characterized by XRD, FT-IR and SEM. The results of the characterization and the leaching experiments indicated that Zn-Al LDHs was the major phase in the composite samples, and strontium was removed by substituting the zinc in the crystalline lattice of Zn-Al LDHs or by bonding with hydroxyl on the surface or carbonate in the interlayer of Zn-Al LDHs. In situ electrochemical synthesis method of Zn-Al LDHs has been proved feasible for the removal of strontium in LRW.

Evaluation of mercury adsorption and removal efficacy of pulverized Chlorella (C. vulgaris)

Chlorella is a green alga consumed as dietary food supplement in pulverized form. In addition to its high nutritional value, it is reported as an excellent detoxifying agent. Pulverized Chlorella has been reported for removal of cadmium and radioactive strontium from the body. Chlorella adsorbs these metal ions on its surface; thus, the physiological pH of gastrointestinal tract is an important factor which may affect its efficacy. Therefore, the present study aimed to evaluate mercury adsorption and removal efficacy of pulverized Chlorella vulgaris. The adsorption efficacy was investigated in terms of the weight of Chlorella, contact time, mercury concentration, simulated physiological fluids (SGF and SIF) and influence of pH. Langmuir and Freundlich adsorption isotherm models were fitted to determine the maximum adsorption capacity. In addition, mercury removal efficiency of Chlorella was evaluated in mice. The mercury content in major tissues, urine and faeces was estimated. The whole tissue retention of mercury after the treatment with Chlorella was taken as a measure of its mercury removal efficacy. The mercury content was measured using validated atomic absorption spectrometer. Chlorella showed significant increase in adsorption of mercury, and the equilibrium was achieved at 180 min. The maximum adsorption capacity was found to be 111.11, 83.33 and 125 mg g−1Chlorella in water, SGF and SIF, respectively. In mice, Chlorella significantly reduced the deposition of mercury in tissues and facilitated its excretion through faeces. Pulverized Chlorella showed potential adsorption efficiency and may considered a promising agent in counteracting the toxic effects elicited by mercury.

Influence of colloidal Fe(OH)3 on the adsorption characteristics of strontium in porous media from a candidate high-level radioactive waste geological disposal site

Colloids in groundwater or geological barriers generally play a key role in the migration of special nuclides. Adsorption characteristics of strontium were investigated on porous media in the presence of colloidal Fe(OH)3 from the Beishan Site, the only high-level radioactive waste disposal site candidate in China. The effects of colloid amounts, solid contents, and pH were determined and studied by batch texts. The results revealed that the presence of colloidal Fe(OH)3 in porous media contributed to promotion of the sorption effect, and the influencing factors had a significant impact on the adsorption process. The sorption ability increased with increasing colloid amount when the equilibrium time was approximately 10 h under an optimal solid-liquid ratio of 20 g L−1. The sorption effect in alkaline conditions was better than that under acidic conditions. The sorption kinetics indicated that the strong chemical interaction and/or surface complexation contributed primarily to strontium sorption. The sorption isotherms and model fitting revealed that the sorption of strontium onto porous media in the presence of colloidal Fe(OH)3 was a monolayer adsorption, and the presence of colloidal Fe(OH)3 is an important factor that greatly influences the removal of strontium from aqueous solutions. These findings provide useful information for the treatment of strontium in radioactive waste disposal sites.

Removal of barium and strontium from wastewater and radioactive wastes using a green bioadsorbent, Salvadora persica (Miswak)

Removal of barium and strontium from wastewater and radioactive wastes using a green bioadsorbent, Salvadora persica (Miswak)

Modeling and optimization of removal of strontium and cesium from aqueous streams by size enhanced ultrafiltration using chitosan derivative

Modeling and optimization of removal of strontium and cesium from aqueous streams by size enhanced ultrafiltration using chitosan derivative

Selectivity of Ar/O2 plasma-treated carbon nanotube membranes for Sr(II) and Cs(I) in water and wastewater: Fit-for-purpose water treatment

The need for high-performance and novel technologies for selective treatment of radionuclides in water has recently stimulated broad research. In this study, we examined the ability of carbon nanotube (CNT) membranes in selective removal of strontium (Sr2+) and cesium (Cs+) from water and wastewater. In single-metal systems that contained only Sr2+, Cs+ or their competitive metal ions, the distribution coefficients (Kd) of functionalized CNT membranes for divalent cations, i.e., Sr2+, Ca2+, and Mg2+, were measured as 4.41 mmol g−1, 2.14 mmol g−1, and 1.30 mmol g−1, respectively, and those for monovalent cations, i.e., Cs+, K+ and Na+, were 0.81 mmol g−1, 0.79 mmol g−1, and 0.81 mmol g−1, respectively. When Cs+ or Sr2+ co-existed with a competing cation, both pristine and functionalized CNT membranes showed excellent selectivity to Sr2+ over Mg2+ and Ca2+ while their selectivity to Cs+ over K+ and Na+ diminished. Moreover, the CNT membranes remained their selectivity for Sr2+ in a wastewater effluent despite the complex water composition. Overall, the selectivity sequence of the CNT membranes for divalent cations support the occurrence of inner-sphere complexation on CNT surfaces, while that for the monovalent cations was probably determined by electrostatic interactions. This study demonstrates that Ar/O2 plasma treatment is a greener technology for the production of CNT functionalized membranes for selective removal of contaminants from water to achieve “fit-for-purpose” treatment.

Investigation of interaction behaviours of cesium and strontium ions with engineering barrier material to prevent leakage to environmental

This study deals with performance of removal of cesium (Cs+) and strontium (Sr2+) ions from synthetic aqueous solution using amino pyridine sulfone amid resin as a barrier material for nuclear waste storage areas to reduce environmental risk. The effects of adsorbate concentration, temperature and contact time on the efficiencies of the engineering barrier material for Cs+ and Sr2+ ions were investigated and evaluated. It was found that total adsorption capacity was higher for cesium ions than strontium ions. Dubinin–Radushkevich (D-R) isotherm model was well fitted to the adsorption data for both ions. The micropore capacity of the barrier material was found as 4.20 mg for strontium ions and 5.40 mg for cesium ions. ΔH values were indicated that the interaction process is exothermic for both ions. The positive value of entropy for both ions show that randomness at the solid-solution interface increased. Pseudo-second-order model was well fitted the kinetic data.

A novel nanomaterial and its new application for efficient radioactive strontium removal from tap water: KZTS-NS metal sulfide adsorbent versus CTA-F-MF process

Developing materials with excellent adsorption performance and evaluating their feasibility for practical use are highly demanded for radioactive strontium removal from natural water. Herein, a novel K/Zn/Sn/S metal sulfide nanosheet (KZTS-NS) is prepared using a hydrothermal method. The powdered KZTS-NS consists of Lewis basic Zn/Sn/S layers and exchangeable K+, which are favorable for Sr2+ adsorption. Batch adsorption experiments confirmed that KZTS-NS was active in a wide pH range of 3–11. Ultrafast adsorption of Sr2+ was achieved by KZTS-NS with an equilibrium time of only 1 min. KZTS-NS possessed a high maximum adsorption capacity of 55.7 mg/g at 298 K, and demonstrated acceptable irreversibility in DI water and selectivity for Sr2+ adsorption. Negligible hazardous ions were leached, suggesting that KZTS-NS is an environment-friendly material. Unfortunately, Ca2+ and Mg2+ can severely interfere with Sr2+ adsorption in actual natural water. To overcome this limitation, a new application of the powdered adsorbent in a combined process of countercurrent two-stage adsorption-flocculation-microfiltration (CTA-F-MF) was evaluated in actual tap water. The results confirmed that the KZTS-NS-based CTA-F-MF process could fully utilize the adsorption capacity and also avoid the negative influence of the competing ions on Sr2+ adsorption, thus achieving a decontamination factor (DF) of Sr2+ as high as 1405. Only 19.5 mL of solid waste was generated when 1.8 L of tap water was treated. The results demonstrate that KZTS-NS is a promising nanomaterial with high Sr2+ adsorption performance and could be used practically in the CTA-F-MF process for the efficient removal of Sr2+ from tap water.

Designing yeast as plant-like hyperaccumulators for heavy metals

Hyperaccumulators typically refer to plants that absorb and tolerate elevated amounts of heavy metals. Due to their unique metal trafficking abilities, hyperaccumulators are promising candidates for bioremediation applications. However, compared to bacteria-based bioremediation systems, plant life cycle is long and growing conditions are difficult to maintain hindering their adoption. Herein, we combine the robust growth and engineerability of bacteria with the unique waste management mechanisms of plants by using a more tractable platform-the common baker’s yeast-to create plant-like hyperaccumulators. Through overexpression of metal transporters and engineering metal trafficking pathways, engineered yeast strains are able to sequester metals at concentrations 10–100 times more than established hyperaccumulator thresholds for chromium, arsenic, and cadmium. Strains are further engineered to be selective for either cadmium or strontium removal, specifically for radioactive Sr90. Overall, this work presents a systematic approach for transforming yeast into metal hyperaccumulators that are as effective as their plant counterparts.

Synthesis of carboxyl group functionalized silica composite resin for strontium removal

Radioactive strontium 90Sr with a half-life of 29 years is one of the most concerned elements in both nuclear accidents and spent fuel reprocessing. Herein, using macroporous silica SiO2 as support, methylacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linking agent, a novel resin named SiMaC was prepared via in situ polymerization method for strontium removal. The as-preapred SiMaC was characterized by SEM-EDS, TG-DSC, and BET. Various factors such as pH, m/V, time, and initial concentration of Sr(II) were studied. The maximum adsorption capacity towards Sr(II) was as high as 142.5 mg/g at 298 K. The adsorption equilibrium was almost obtained within 30 min. Moreover, SiMaC was easily and fastly regenerated by 0.1 M HCl and exhibited no obvious decrease in adsorption capacity after five times of successive adsorption-desorption cycles. Most attractively, the uptake rate of Sr(II) reached more than 99% in real river and lake water mediums, as well as reached 76% in real seawater mediums. Finally, XPS and FTIR were used to analyze the adsorption mechanism towards Sr(II).

Adsorptive and Kinetic Studies of Resin for Removal of Cs+ and Sr2+ from Aqueous Solution

Mixed bed resin was prepared using T-46 (H+) and A-33 (OH−) through mixing their ratio 1: 1.6 and characterized by Fourier transform infrared scanning electron microscopy and energy dispersive X-Ray spectroscopy. The mixed bed resin was evaluated for the removal of cesium and strontium from contaminated water. The aim of our study was to find the suitable condition for removal of Cs and Sr ions from water under different conditions viz. initial concentration of Cs and Sr ions, contact time, dose of resin and pH. Cs and Sr ions, adsorption data are fitted well with Freundlich and Langmuir isotherm models. The adsorption capacity was 7.53 and 9.58 mg/g for Cs and Sr ions, respectively as obtained at initial concentration 10 mg/L by Langmuir isotherm. Adsorption kinetics was followed by pseudo-second order reaction. The rate constants of pseudo-second order reaction were calculated and quite high correlation coefficients R2 98–99.5 were obtained. The resin also used for removal of Cs and Sr ions from tap water (TDS—200 mg/L) and saline water (TDS—2000 mg/L), and showed 90% (Cs) and 95% (Sr) removal at 10 mg/L of each ion concentration.

The sorption behavior of CHA-type zeolite for removing radioactive strontium from aqueous solutions

The highly efficient removal of radioactive metal ions (e.g.137Cs, 90Sr) remains a challenge from the standpoint of environmental protection and public health. Although adsorption has been proven to be an effective and economical technology to eliminate the radioactive metal ions from aqueous solutions, few adsorption materials have been reported for the efficient removal of 90Sr. In this work, an aluminosilicate with CHA-type zeolite framework was synthesized and investigated for the adsorption of Sr2+ ions. The CHA aluminosilicate zeolite was hydrothermally synthesized with a cost-effective method by employing N,N,N-dimethylethylcyclohexylamine hydroxide as the structure directing agent. Its structure was confirmed by powder X-ray diffraction and N2 sorption experiments. Batch scale experiments suggested that the CHA-type zeolite could efficiently remove Sr2+ ions from aqueous solutions. The sorption process was kinetically fast with a maximum sorption attained within 60 min, and the high sorption capacity can be maintained at varied pH levels (3–11) and temperatures (298–328 K). Regeneration of the adsorbent showed that more than 96% of the initial capacity remains intact after five cycles. Additionally, the CHA zeolite packed in fixed-bed columns enables a continuous efficient removal of strontium for 60 min. Our results suggested that the CHA zeolite could potentially serve as chromatographic column materials for the removal of radioactive Sr2+, prefiguring their great promise for the application in nuclear waste management.

Studies on the separation and in-situ sintering solidification of strontium by a highly-efficient titanate-based adsorbent

Abstract Nuclear accident and daily nuclear plants are the main strontium (Sr 2+ ) releasing source and the removal of strontium from aqueous solution has aroused great attention. Among the different remediation ways, adsorption with the properties of low cost, high-removal efficiency, and excellent operational simplicity is intensively adopted in the removal of hazard ions in aqueous solution. However, adsorbent could be accumulated and might cause secondary solid wastes after the treatment of hazard ions, which increases troubles and challenges in the disposal process. In this work, a sodium titanate powder (Na 2 Ti n O 2n+1 ) was prepared by an improved sol-gel method. The X-ray diffraction (XRD) demonstrates that Na 2 Ti n O 2n+1 is transformed into anatase structure after calcining at 400 °C for 10h. The specific surface area (BET) of the synthesized adsorbent is 65.01 m 2 /g. The results of batch adsorption experiments reveal that Na 2 Ti n O 2n+1 is a promising adsorbent for removing Sr 2+ , which the maximum adsorption capacity could achieve to 49.6 mg/g. The adsorbent also shows high selectivity towards Sr 2+ in the co-existence ions of Ba 2+ , Ca 2+ , Mg 2+ , Cs + , K + , and the affinity order is Sr 2+ > Ba 2+ > Ca 2+ > Mg 2+ >Cs + >K + . In the solidification stage, Sr–Na 2 Ti n O 2n+1 adsorbent is cold pressed at 40Mp and then calcined into titanate ceramics (Na–Sr-Ti n O 2n+1 ) at 1100 °C. The leaching experiment of titanate ceramics on various medium exhibits excellent solidification capability towards adsorbed Sr 2+ .

Application of fly ash-based geopolymer for removal of cesium, strontium and arsenate from aqueous solutions: kinetic, equilibrium and mechanism analysis.

Geopolymerization is a developing reaction process for the utilization of solid wastes. In the present study, fly ash-based geopolymer and its derivative (Fe(II)-modified geopolymer) were synthesized and characterized using XRD, SEM, FTIR, BET, UV-Vis DRS as well as TG-DTA, and adopted as adsorbents for removal of Cs+ and Sr2+, and AsO3- 4 from solutions. Each sorption kinetic was well fitted to the pseudo-second-order model. The sorption of Cs+ and Sr2+ onto original geopolymer were better fitted to the Langmuir model. However, the Freundlich model is more befitting for sorption of AsO3- 4 onto Fe(II)-modified geopolymer. The free energies calculated from the D-R isotherm indicated that the sorption for Cs+ and Sr2+ were dominantly ion exchanges. Ring size plays a decisive role in ion exchanges for both Cs+ and Sr2+. Furthermore, the arrangement of SiO4 and AlO4 tetrahedrons has significant impacts on the ion exchange of Sr2+. XPS results indicated that a part of Fe2+ in Fe (II)-modified geopolymer had been oxidized to Fe3+ after sorption. Precipitation of FeAsO4 could partially contribute to the arsenate removal from solution. AsO3- 4sorption has also occurred through the formation of inner-sphere complexes via ion exchange reaction, which could be predominantly attached by bidentate linkages.

Removal of strontium from aqueous solutions by sodium dodecyl sulfate-modified palygorskite

Palygorskite (PAL) was modified with sodium dodecyl sulfate (SDS) for the removal of Sr(II) from aqueous solutions. Analysis of the structural characteristics of PAL before and after modification showed that PAL was successfully modified with SDS. Sorption experiments were conducted in batch mode under optimum conditions to evaluate the effect of initial pH and co-existing ions on the removal of Sr(II) by SDS-modified PAL. The equilibrium sorption isotherm data for Sr(II) were analyzed using Freundlich and Langmuir isotherm sorption equations, and the data fitted well to the Freundlich isotherm model. Pseudo-first-order and pseudo-second-order kinetic models were examined, and the sorption of Sr(II) showed better agreement with the pseudo-second-order kinetic model (r2 > 0.99). The desorption experiments indicated that the SDS-modified PAL having sorbed Sr(II) does not release significant amounts of Sr(II) into the environment under natural conditions, thus avoiding secondary pollution.

Preparation of new magnetic zeolite nanocomposites for removal of strontium from polluted waters

Efficient separation of strontium ions (Sr2+) from waters has become a critical technological requirement after the nuclear accident at Fukushima Daiichi power station. In the present investigation, new nanocomposites of zero valent iron nanoparticles–zeolite (nZVI–Z) and nano-Fe/Cu–zeolite (nFe/Cu–Z) were synthesized via a simple liquid-phase reduction approach and tested to determine their effectiveness in the sorptive removal of Sr2+ from aqueous solutions. The sorption of Sr2+ on both nanocomposites was studied in a batch sorption mode as a function of various environmental conditions such as initial Sr2+ concentration, contact time, pH, temperature, dosage of sorbent and competing cations (Na+, K+, Mg2+ and Ca2+). The results indicated that initial pH and temperature were significant for Sr2+ sorption on both nanocomposites. The Sr2+ sorption efficiency increases with the increase in nanocomposite dosage and decreases with the Sr+2 concentration. It was also found that although the sorption of Sr2+ was decreased by the presence of coexisting cations, the nanocomposites still exhibited high uptake capacity of Sr2+ ions. The Sr2+ sorption kinetics can be satisfactorily fitted by a pseudo-second-order kinetic model. The sorption isotherm data were well predicted using the Langmuir model. The maximum sorption capacity for nFe/Cu–Z was found to be 88.74 mg/g, which was greater than that for nZVI–Z (84.12 mg/g). In addition to the high sorption capacity, the nanocomposites could be easily separated from aqueous media after Sr2+ sorption using an external magnetic field. The calculated thermodynamic parameters such as ∆H°, ∆S° and ∆G° revealed the endothermic and spontaneous nature of the sorption process. The nanocomposites were also applied in a real seawater medium. The present study confirmed that the prepared nZVI–Z and nFe/Cu–Z nanocomposites could be employed as promising methods for the removal of Sr2+ from wastewater streams.

Removal and recovery of strontium (Sr(II)) from seawater by Fe3O4/MnO2/fulvic acid nanocomposite

In this study, Fe3O4/MnO2/FA nanocomposite was synthesized as a low cost adsorbent with high adsorption capacity, desorption efficiency and reusability for Sr(II) extraction from seawater. FT-IR, FESEM-EDS, XRD, VSM and BET experiments were used to characterize the composite. Sr(II) adsorption onto Fe3O4/MnO2/FA followed a pseudo-first-order kinetic model and was well fitted with the Langmuir isotherm model. Fe3O4/MnO2/FA has demonstrated an excellent adsorption capacity of 227.3 mg/g for Sr(II) ions at 25 °C and pH 8. The composite showed high selective uptake of Sr(II) in the presence of cations Na, Mg and Ca. However, Ca ions reduced the Sr(II) uptake from 49.1 to 41.0 mg/g at 600 mg/L Ca. Sr(II) desorption was performed using 0.1 M HCl which showed an excellent desorption efficiency. In natural seawater containing 9.4 mg/L Sr(II), without changing the physicochemical conditions, Fe3O4/MnO2/FA composite showed 6.4 mg/g of Sr(II) adsorption, which leads to save time and energy consumption.

Carbonaceous materials synthesized from thermally treated waste materials and its application for the treatment of Strontium metal solution: Batch and optimization using Response Surface Methodology

Abstract Strontium is one of the major components discharged from nuclear power plant, ceramic industry and fire cracker manufacturing Industry. Due to usage of strontium in various fields, the disposal of the wastes is often found to be inadequate. Strontium has an innate ability to replace calcium in bones and food chain may get affected by the bioaccumulative property of strontium. In this paper, thermally activated sawdust was used for removal of strontium present in solution. This work was mainly focused on removal of strontium from aqueous solution by batch study and optimization of the process parameter was performed using Response Surface methodology (RSM). 95% removal was obtained by using 100 mg/ml adsorbent dose, at 308.15 K temperature and pH 8 in batch study. The maximum removal of Sr+2 was obtained at pH: 7.41 with temperature: 326.15 K, and adsorbent dose: 14 g/L by using RSM. Three types of adsorbent were used in this study raw sawdust (SDR), thermally activated sawdust at 623.15 K (SDTh1) and thermally activated sawdust at 973.15 K (SDTh2) and it was observed that SDTh2 was best among the three adsorbent.

Preparation of Sulfonylcalix[4]arene-loaded XAD-7 Resin for Strontium(II) Adsorption

Sulfonylcalix[4]arene-loaded XAD-7 Resin was prepared and used as an adsorbent for removal of Strontium(II) from aqueous solutions. The adsorption of the metal ions onto SCA-XAD-7 as a function of pH, contact time, metal ions concentration, temperature, and reuses was investigated. The adsorption capacity of SCA-XAD-7 composite towards tested ions reached a maximum at pH values of ∼6. The adsorption has reached equilibrium within 7 h. The adsorption isotherms were well fitted by the Langmuir model, and the maximum values of adsorption capacity of the adsorbent were 28.87 mg⋅g−1. Thermodynamic studies imply the adsorption was a spontaneous and exothermic process in nature.