Removal Of Strontium Research Articles

Decorating Channel Walls in Metal–Organic Frameworks with Crown Ethers for Efficient and Selective Separation of Radioactive Strontium(II)

AbstractNuclear accidents and the improper disposal of nuclear wastes have led to serious environmental radioactive pollutions. The rational design of adsorbents for the highly efficient separation of strontium(II) is essential in treating nuclear waste and recovering radioactive strontium resources. Metal–organic frameworks (MOFs) are potential materials for the separation of aqueous metal ions owing to their designable structure and tunable functionality. Herein, a novel 3D MOF material MOF‐18Cr6, in which 1D channels are formed using 18‐crown‐6‐ether‐containing ligands as channel walls, is fabricated for strontium(II) separation. In contrast to traditional MOFs designed by grafting functional groups in the framework pores, MOF‐18Cr6 possesses regular 18‐crown‐6‐ether cavities on the channel walls, which not only can transport and intake strontium(II) via the channels, but also prevent blockage of the channels after the binding of strontium(II). Consequently, the functional sites are fully utilized to achieve a high strontium(II) removal rate of 99.73 % in simulated nuclear wastewater. This study fabricates a highly promising adsorbent for the separation of aqueous radioactive strontium(II), and more importantly, can provide a new strategy for the rational design of high‐performance MOF adsorbents for separating target substances from complex aqueous environments.

Performance of Thermal-, Acid-, and Mechanochemical-Activated Montmorillonite for Environmental Protection from Radionuclides U(VI) and Sr(II)

Low-cost sorption materials based on the clay mineral of the smectite group—montmorillonite—were used for the removal of radionuclides uranium (VI) and strontium (II) from contaminated water. A wide range of industrial methods such as thermal treatment, acid activation, and mechanochemical activation were applied. Complex methods, such as SEM microscopy analysis, X-ray powder diffraction (XRD), thermal analysis, and nitrogen adsorption–desorption at −196 °C, were used to assess the characteristics of the structure of the obtained materials. The thermal treatment, acid activation, and mechanochemical activation resulted in changes in the surface properties of the clay minerals: specific surface area, porosity, and distribution of active sites. It was established that the mechanochemical activation of montmorillonite significantly increases the sorption characteristics of the material for U(VI) and Sr(II) and the acid activation of montmorillonite increases it for U(VI). The appropriateness of the experimental adsorption values for U(VI) and Sr(II) on modified montmorillonite to Langmuir and Freundlich models was found. Independently of the changes induced by acid attack, calcinations, or milling, the sorption of U(VI) and Sr(II) ions on treated montmorillonite occurs on a homogeneous surface through monolayer adsorption in a similar fashion to natural montmorillonite. Water purification technologies and modern environmental protection technologies may successfully use the obtained clay-based sorbents.

Fast removal of strontium from nitric acid solution using an acid-resistant silica-based adsorbent

To efficiently separate strontium (Sr) from simulated high level liquid waste (HLLW), a novel acid-resistant inorganic-organic hybrid adsorbent, named as HEMAP/SiO2-P, was prepared by loading 2-hydroxyethyl-2-methyl-2-propenoate phosphate (HEMAP) into styrene-divinylbenzene modified silica (SiO2-P) with vacuum impregnation method. The experimental results showed that the adsorbent exhibited good adsorption selectivity with the SFSr/metal ions over 64.2 in 3 M HNO3 simulated HLLW. In addition, the adsorption of Sr by the adsorbent was in accordance with the pseudo-second-order kinetic model and the Langmuir isotherm model, and the adsorption equilibrium was obtained within 1 min with the saturation adsorption capacity of 61.2 mg/g. The adsorption of Sr was not markedly changed with increasing temperature. Furthermore, the results of adsorption experiments, characterization analysis, extraction experiments and density functional theory (DFT) calculations revealed that two organic ligand molecules were coordinated with one Sr molecule and simultaneously involved two nitrate molecules to maintain the charge balance during the adsorption process.

Removal of cobalt and strontium by adsorption using Brewer's spent grain formed by pyrolysis.

One byproduct of brewing beer is Brewer's spent grain (BSG), which is reused in animal feed. However, BSG has valuable potential for other products such as biochar because of its high protein and fiber content. Radioactive waste is one of the biggest concerns in Korea because of the permanent shutdown of the Gori nuclear power plant. In this study, we aimed to use BSG-850, a biochar originating from BSG after pyrolysis at 850°C, for the adsorption of cobalt (Co) and strontium (Sr), which are two radionuclides that contribute to radioactive waste. The adsorption capacity of Co and Sr was reinforced with increased temperature which are 3.304, 4.659, 5.516mg/g (Co) and 1.462, 2.54, 3.036mg/g (Sr) at 298, 308, and 318K, respectively. The reusability of BSG-850 capacity was 75.3, 47.8, 43.6, 36.2% and 93.6, 84.2, 57.2, and 32.7% after 1, 2, 3, and 4 cycles, for Co and Sr, respectively. In the presence of other competitive ions, the adsorption capacity decreased. The adsorption capacity and properties of BSG-origin biochar for Co and Sr were confirmed and BSG can be a desirable option for solving radioactive waste issue.

Study of ultrasound, initial concentration and electrode material on the electrochemical removal of selenium and strontium

Since high concentrations of selenium and strontium in water can potentially harm human health, various methods have been developed for their treatment. The objective of this paper was to validate previously published studies on the electrochemical removal of selenium and strontium, while also reducing the reactor operating time and using an ultrasound assisted process. After careful evaluation of the preliminary experiments, a combination of aluminum and iron electrodes was identified as the most suitable option for further investigation. The Design of Experiments approach was utilized to study the effects of ultrasound intensity (0%, 50%, 100%), operating time (2, 6, 10 minutes), applied current (2.5, 7.5, 12.5 A), and initial concentrations of selenium and strontium (1, 3, 5 mg L−1) on the sono-electrochemical removal of selenium and strontium from a synthetic solution. A modified ultrasonic bath, operating at 25 kHz, was used for all the experiments. The results showed that ultrasound and the initial selenium and strontium concentrations had no effect on the removal efficiency. The obtained reduced quadratic models predicted a removal efficiency of 93% for selenium and 34% for strontium under the optimal conditions, which included 10 minutes of operation and 12.5 A of current.

Development of environment-friendly magnetic nanobiocomposites and full factorial design (FFD) analysis for strontium removal from aqueous solutions

Development of environment-friendly magnetic nanobiocomposites and full factorial design (FFD) analysis for strontium removal from aqueous solutions

A novel Sn/SnOx Ti3C2Tx nanosheet for adsorptive strontium removal in aqueous solution

A novel Sn/SnOx@Ti3C2Tx adsorbent was fabricated via in situ growth of Sn/SnOx particles on layers of Ti3C2Tx nanosheets using facile electrostatic attraction followed by liquid-phase reduction. The characterization results demonstrated that Sn/SnOx particles were uniformly anchored onto the Ti3C2Tx surface and a sandwich-like-structured nanocomposite was formed. The introduction of Sn/SnOx particles increased the space between the Ti3C2Tx nanosheets, thereby increasing the number of active sites for Sr2+ ion removal. Moreover, the incorporated particles served as pillars to strengthen the structural stability of the Ti3C2Tx matrix and inhibited nanolayer restacking during Sr2+ion removal. Experimental results indicated that an initial strontium concentration of 5.0 mg/L was reduced to approximately 0.26 mg/L by Sn/SnOx@Ti3C2Tx within 90 min at pH 7. Furthermore, the Langmuir isotherm best fitted the adsorption data, and the maximum adsorption capacity of Sn/SnOx@Ti3C2Tx for Sr2+ ions was 71.04 mg/g at 298 K. Thus, Sn/SnOx@Ti3C2Tx nanocomposites is a promising adsorbent for the removal of Sr2+ ions from aqueous media.

Efficient removal of Sr2+ ions by a one-dimensional potassium phosphatoantimonate

90Sr is one of the most dangerous artificial radionuclides. 90Sr generally exists in the form of 90Sr2+ ions in radioactive waste liquids. The efficient removal of radioactive strontium from the complex aqueous environments remains a challenge due to high solubility and easy migration of 90Sr2+ ions and the complex compositions of the radioactive waste liquids. Herein, a one-dimensional potassium phosphatoantimonate (1D-K2SbPO6) with the low cost presents the efficient removal of Sr2+ ions. It possesses the wide pH durability, excellent irradiation resistance and thermal stability. It exhibits the high adsorption capacity of qm = 175.90 mg/g and excellent selectivity for Sr2+ ions in the presence of competing Na+, Cs+, Mg2+ and Ca2+ ions and even in actual aqueous systems. The Sr2+ removal mechanism of K2SbPO6 is attributed to the ion exchange between Sr2+ and easily exchangeable K+ ions located between the [SbPO6]n2n− chains in K2SbPO6. K2SbPO6 is the first example of antimonate(V)-based ion exchange materials with a one-dimensional structure for the Sr2+ capture. This work paves the way to the design and synthesis of new inorganic antimonite (V)-based ion exchange materials for radionuclides remediation.

Removal of strontium by ion exchange and lime softening at eight drinking water treatment plants

The United States (US) Environmental Protection Agency (EPA) included strontium (Sr) in the Contaminant Candidate List 3 as a chemical for potential future regulatory consideration.

Strontium removal from aquatic solution using electric arc furnace slag: kinetic, equilibrium and thermodynamic approach

Strontium removal from aquatic solution using electric arc furnace slag: kinetic, equilibrium and thermodynamic approach

Development of titanium doped hydroxyapatite for efficient removal of radioactive strontium from contaminated water

In this study, we focused on synthesizing an efficient composite material for the decontamination of non-radioactive surrogates of strontium and extensively studied the adsorption and thermodynamic parameters.

Response surface methodology approach for optimization of removal of strontium by in-situ electrochemical synthesis of monohydric phosphate intercalated layered double hydroxides

Response surface methodology approach for optimization of removal of strontium by in-situ electrochemical synthesis of monohydric phosphate intercalated layered double hydroxides

Efficient Capture of Sr2+ Ions by a Layered Potassium Neodymium Phosphate

90Sr has a long half-life, strong radioactivity, and high mobility. The removal of radioactive strontium from the water environment is of great significance to human safety and the sustainable development of nuclear energy. In this study, a two-dimensional rare earth phosphate K3Nd(PO4)2 efficiently captured Sr2+ ions in aqueous solutions. At room temperature, the adsorption isotherm, kinetics, and pH dependence experiments of K3Nd(PO4)2 for Sr2+ ions were examined (V/m = 1000 mL/g, 12 h contact time). The experimental results show that the maximum adsorption capacity of K3Nd(PO4)2 for Sr2+ (qmSr) was 42.35 mg/g. The removal efficiency for Sr2+ (RSr) was 87.47% within 24 h. It had a good affinity with Sr2+ ions in neutral or even high alkaline environments (distribution coefficient KdSr = 1.46 × 106 mL/g, RSr = 99.93%). The adsorption mechanism was attributed to the ion exchange between Sr2+ and K+ ions by batch adsorption experiments combined with multiple characterizations, including XPS, EDS, and PXRD. This is the first report of Sr2+ removal by ion exchange via rare earth phosphate materials with a two-dimensional structure. This work provides insight into the future development of rare earth phosphates as ion exchange materials for radionuclide remediation.

Removal of cesium and strontium for radioactive wastewater by Prussian blue nanorods.

In this work, novel Prussian blue tetragonal nanorods were prepared by template-free solvothermal methods to remove radionuclide Cs and Sr. The as-prepared Prussian blue nanorods were identified and characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopic, thermogravimetric analysis, zeta potential, and surface analysis, and its sorption performance was tested by batch experiments. Our results suggest that Prussian blue nanorods exhibited better adsorption performance than co-precipitation PB or Prussian blue analogue composites. Thermodynamic analysis implied that the adsorption process was spontaneous and endothermic which was described well with the Langmuir isotherm and pseudo-second-order equation. The maximum adsorption capacity of PB nanorod was estimated to be 194.26mgg-1 and 256.62mgg-1 for Cs+ and Sr2+(adsorbate concentration at 500mg L-1, the temperature at 298k, pH at 7.0). Moreover, the experimental results showed that the Prussian blue nanorods have high crystallinity, few crystal defects, and good stability under alkaline conditions. The adsorption mechanism of Cs+ and Sr2+ was studied by X-ray photoelectron spectroscopy, X-ray diffraction, and 57Fe Mössbauer spectroscopy. The results revealed that Cs+ entered the PB crystal to generate a new phase, and most of Sr2+ was trapped in the internal crystal and the other exchanged Fe2+. Furthermore, the effect of co-existing ions and pH on PB adsorption process was also investigated. The results suggest that PB nanorods were an outstanding candidate for removing Cs+ and Sr2+ from radioactive wastewater.

Fabrication of cobalt iron oxide alginate nanocomposite as an eco-friendly sorbent for Y(III) and Sr(II) removal from aqueous solution

Alginate cobalt iron oxide, Alg-CoFe2O4 nanocomposite was synthesized by ionic polymerization method and employed as a magnetically separable low-cost sorbent for yttrium and strontium removal from an aqueous phase. The produced nanocomposite was characterized using x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. The hysteresis loop of the nanocomposite, obtained by the vibrating sample magnetometer, shows a soft magnetic behavior with a saturation magnetization of about 6.96 emu/g. The optimum pH for the sorption of Y(III) and Sr(II), studied by the batch mode, was found to be 4.7 and that ion exchange is not the only mechanism in the sorption process. The obtained kinetic data of Y(III) and Sr(II) was analyzed using the reaction rate and diffusion models and it was found that the pseudo-second-order fits well the data with a high correlation coefficient > 0.99. The isotherm study revealed that the sorption of Y(III) was well described by the Freundlich model, whereas the Langmuir model provided the best fit for the sorption of Sr(II).The maximum sorption capacity of the nanocomposite was 78.22 mg/g for Y(III) and 47.5 mg/g for Sr(II). Furthermore, Y(III) and Sr(II) were recovered from the loaded nanocomposite with a high desorption percentage using 1.0 mol/L of HNO3 demonstrating its reusability. It can be concluded based on the results that the Alg-CoFe2O4 nanocomposite has good sorption potential of Y(III) and Sr(II).

Adsorption of Sr(II) in aqueous solution by multilayer titanium carbon nitrogen (Ti3CNTx) MXene: Box-Behnken modeling design and experimental study

The discharge of low-level radioactive wastewater from nuclear power accidents is an important source of radionuclides that enter and pollute the environment, such as 90Sr, which has a long half-life and is harmful. The effectiveness of multilayer Ti3CNTx MXene as a novel adsorbent for the removal of wastewater containing Sr2+ was explored. The synthesized multilayer Ti3CNTx MXene was characterized by XPS, FTIR, SEM, BET, and XRD. The influence of basic process parameters, such as time, pH, coexisting ion concentration, and initial concentration, on strontium adsorption efficiency, was determined. Ti3CNTx showed rapid kinetics (nearly 90% strontium removal after 15 min) and a broad active pH range of 3–12. The adsorption capacity of Ti3CNTx was better than that of Ti3C2Tx under the same reaction conditions. The maximum adsorption capacity of Ti3CNTx was 26.53 mg∙g−1 at 313 K according to the Langmuir isotherm. And the adsorption was consistent with the pseudo-second-order kinetic. The experiments of initial concentration and coexisting ions showed that the Ti3CNTx has a high affinity for strontium at low concentration, and the inhibition of Ca2+ is the largest. Ti3CNTx adsorbed Sr2+ via complex formation, electrostatic attraction, and encapsulation as revealed by various instrument characterization and analysis. The reusability of Ti3CNTx was good, after four cycles, the removal efficiency was 73%. Finally, the RSM model was applied to explore the optimal conditions of adsorbent to provide a reference for practical application. In conclusion, the results showed that the multilayer Ti3CNTx MXene has a good adsorption performance for strontium.

The effect of organic impurities on the efficiency of strontium removal by sorbents based on manganese oxide

The effect of organic impurities on the efficiency of strontium removal by sorbents based on manganese oxide

Three-dimension titanium phosphate aerogel for selective removal of radioactive strontium(II) from contaminated waters

The effective removal of radioactive strontium (especially 90Sr) from nuclear wastewater is crucial to environmental safety. Nevertheless, materials with excellent selectivity in Sr removal remain a challenge since the similarity with alkaline earth metal ions in the liquid phase. In this work, a novel titanium phosphate (TiP) aerogel was investigated for Sr(II) removal from the radioactive wastewater based on the sol-gel method and supercritical drying technique. The TiP aerogel has amorphous, three-dimensional and mesoporous structures with abundant phosphate groups, which was confirmed by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR). The adsorbent exhibited high efficiency and selectivity for the removal of Sr(II) with an extensive distribution coefficient up to 4740.03 mL/g. The adsorption equilibrium reached within 10 min and the maximum adsorption capacity was 373.6 mg/g at pH 5. And the kinetics and thermodynamics data fitted well with the pseudo-second-order model and Langmuir model respectively. It can be attributed to the rapid trapping and slow intraparticle diffusion of Sr(II) inside the mesoporous channels of the TiP aerogel. Furthermore, TiP aerogel exhibited over 80% removal for 50 mg/L Sr2+ in real water systems (seawater, lake water and tap water). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that strong ionic bonding formed during Sr(II) adsorption with the phosphate group on TiP aerogel. These results indicated that TiP aerogel is a promising high-capacity adsorbent for the effective and selective capture of Sr(II) from radioactive wastewater.

Microwave-assisted synthesis of MnO2 nanosorbent for adsorptive removal of Cs(I) and Sr(II) from water solutions.

In this study, a flower-like porous δ-MnO2 nanostructure was synthesized by a microwave-assisted hydrothermal process for adsorptive removal of strontium (Sr(II)) and cesium (Cs(I)) from wastewater. The prepared δ-MnO2 nanosorbent exhibited superior affinity for Sr(II) over Cs(I) in the single-solute system, with partition coefficient (PC) values of 10.2 and 2.3L/g, respectively, at pH 6.0. In the two-solute system, the flower-like δ-MnO2 also adsorbed Sr(II) (PC=3.81L/g) more selectively than Cs(I) (PC 1.15L/g). Further, their adsorption capacities decreased by 12 and 16%, respectively, relative to the single-solute system. In contrast, adsorption of the ions onto δ-MnO2 was affected less sensitively in dual than in single system when changes occurred in environmental variables such as pH (2-8) and ionic strength (1-100mM). Adsorption kinetics, thermodynamics, and isotherm studies demonstrated the pivotal role of the monolayer surface active sites of endothermic δ-MnO2 (e.g., a complexation interaction with Mn-OH). Furthermore, the δ-MnO2 nanosorbent exhibited good regenerability, retaining more than 80% of its adsorption capacity when tested over four reuse cycles. The overall results of this study are expected to help establish strategies to effectively remove metal contaminants from wastewater using a green and low-cost hierarchical nanosorbent.

Designer biochar with enhanced functionality for efficient removal of radioactive cesium and strontium from water

Radioactive elements released into the environment by accidental discharge constitute serious health hazards to humans and other organisms. In this study, three gasified biochars prepared from feedstock mixtures of wood, chicken manure, and food waste, and a KOH-activated biochar (40% food waste + 60% wood biochar (WFWK)) were used to remove cesium (Cs+) and strontium (Sr2+) ions from water. The physicochemical properties of the biochars before and after adsorbing Cs+ and Sr2+ were determined using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, extended X-Ray absorption fine structure (EXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDX). The WFWK exhibited the highest adsorption capacity for Cs+ (62.7 mg/g) and Sr2+ (43.0 mg/g) among the biochars tested herein. The removal of radioactive 137Cs and 90Sr exceeded 80% and 47%, respectively, in the presence of competing ions like Na+ and Ca2+. The functional groups present in biochar, including –OH, –NH2, and –COOH, facilitated the adsorption of Cs+ and Sr2+. The Cs K-edge EXAFS spectra revealed that a single coordination shell was assigned to the Cs–O bonding at 3.11 Å, corresponding to an outer-sphere complex formed between Cs and the biochar. The designer biochar WFWK may be used as an effective adsorbent to treat radioactive 137Cs- and 90Sr-contaminated water generated during the operation of nuclear power plants and/or unintentional release, owing to the enrichment effect of the functional groups in biochar via alkaline activation.